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Quantum spins mimic refrigerator magnets - Argonne National Laboratories,
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Highlights > Quantum spins mimic refrigerator Highlights > Quantum spins mimic refrigerator magnets Quantum spins mimic refrigerator magnets By Joseph Bernstein * October 11, 2012 The behavior of magnetic moments in metal oxides such as layered iridium is dominated by strong spin-orbit coupling effects. In layered compounds such as Sr3Ir2O7 (shown on the left), the direction of these moments (blue arrows) is controlled at the quantum level by dipolar interactions that are akin to those of classical bar magnets. Another outcome is an unprecedented 'magnon gap' (shown at right), which was measured at the Argonne Advanced Photon Source and reveals that these underlying dipolar magnetic interactions are extremely strong. Current electronic devices depend on manipulating charge. Alternative approaches may rely on not only charge but also the spin of electrons.
Magnetic Monopoles in Spin Ice
E-Print Network (OSTI)
Electrically charged particles, such as the electron, are ubiquitous. By contrast, no elementary particles with a net magnetic charge have ever been observed, despite intensive and prolonged searches. We pursue an alternative strategy, namely that of realising them not as elementary but rather as emergent particles, i.e., as manifestations of the correlations present in a strongly interacting many-body system. The most prominent examples of emergent quasiparticles are the ones with fractional electric charge e/3 in quantum Hall physics. Here we show that magnetic monopoles do emerge in a class of exotic magnets known collectively as spin ice: the dipole moment of the underlying electronic degrees of freedom fractionalises into monopoles. This enables us to account for a mysterious phase transition observed experimentally in spin ice in a magnetic field, which is a liquid-gas transition of the magnetic monopoles. These monopoles can also be detected by other means, e.g., in an experiment modelled after the celebrated Stanford magnetic monopole search.
Claudio Castelnovo; Roderich Moessner; Shivaji L. Sondhi
Nano-Signals Get a Boost from Magnetic Spin Waves
Science Conference Proceedings (OSTI)
Nano-Signals Get a Boost from Magnetic Spin Waves. ... Electrical measurement of spin-wave interactions of proximate spin transfer nano-oscillators. ...
Magnetization rotation or generation of incoherent spin waves? Suggestions for a spin-transfer effect experiment.
SciTech Connect
''Spin-transfer'' torque is created when electric current is passed through metallic ferromagnets and may have interesting applications in spintronics. So far it was experimentally studied in ''collinear'' geometries, where it is difficult to predict whether magnetization will coherently rotate or spin-waves will be generated. Here we propose an easy modification of existing experiment in which the spin-polarization of incoming current will no longer be collinear with magnetization and recalculate the switching behavior of the device. We expect that a better agreement with the magnetization rotation theory will be achieved. That can be an important step in reconciling alternative points of view on the effect of spin-transfer torque.
Bazaliy, Y. B.; Jones, B. A.
Spin precession modulation in a magnetic bilayer
We report on modulation of the spin precession in a Co/garnet bilayer by femtosecond laser excitation using time-resolved magneto-optical tools. Damped oscillations in the Faraday rotation transients representing precessional motion of the magnetization vector are observed in both the 2 nm Co layer and 1.8 {mu}m garnet of the bilayer with distinct frequencies differing by about a factor of two. The excitation efficiency of these precessions strongly depends on the out-of-plane magnetic field. The modulation effect with the coupling in a magnetic bilayer can be useful for non-thermally controlling the magnetization of nanomagnets and ultrafast switching in magnetic nanodevices.
Stupakiewicz, A.; Maziewski, A. [Laboratory of Magnetism, Faculty of Physics, University of Bialystok, Lipowa 41, Bialystok (Poland); Pashkevich, M. [Laboratory of Magnetism, Faculty of Physics, University of Bialystok, Lipowa 41, Bialystok (Poland); Scientific-Practical Materials Research Centre of the NASB, P. Brovki 19, Minsk (Belarus); Stognij, A.; Novitskii, N. [Scientific-Practical Materials Research Centre of the NASB, P. Brovki 19, Minsk (Belarus)
Tunable Polarization of Spin Polarized Current by Magnetic Field
The spin polarization of a high g-factor bulk semiconductor is theoretically investigated in the presence of a magnetic field parallel to a driving electric field. Calculations have been carried out using the energy-dependent relaxation time approximation in association with spin-flip scattering. As the magnitude of the magnetic field increases, the spin-polarized current alternates between the spin-up and spin-down states for the low spin-scattering system. This implies that the current polarization can be tuned by controlling the magnetic field strength, suggesting possible applications to spintronic devices. An experimental method for investigating alternative current polarization is also considered.
Joo, S.; Kim, K.; Lee, J.; Kim, T.; Rhie, K.; Hong, J.; Shin, K-H.
Spin microscope based on optically detected magnetic resonance
DOE Patents (OSTI)
The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.
Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)
The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of impaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.
Magnetic charge crystals imaged in artificial spin ice
Magnetic charge crystals imaged in artificial spin ice Magnetic charge crystals imaged in artificial spin ice Magnetic charge crystals imaged in artificial spin ice Potential data storage and computational advances could follow August 27, 2013 Potential data storage and computational advances could follow A 3-D depiction of the honeycomb artificial spin ice topography after the annealing and cooling protocols. The light and dark colors represent the north and south magnetic poles of the islands. Image by Ian Gilbert, U. of I. Department of Physics and Frederick Seitz Materials Research Laboratory Contact Nancy Ambrosiano Communications Office (505) 667-0471 Email Siv Schwink U. Illinois (217) 300-2201 Email "The emergence of magnetic monopoles in spin ice systems is a particular case of what physicists call fractionalization, or deconfinement of
Observation and implications of magnetic domains in lateral spin valves
Co/Cu/Co lateral spin valves (LSV), with Co being the topmost layer, are in situ prepared and measured under ultrahigh vacuum conditions. The clean process yields a non-local spin signal of 0.9 m{Omega}. Scanning electron microscopy with polarization analysis (SEMPA) reveals domain structures in both magnetic electrodes that depend on the LSV dimensions. The spin signal correlates to SEMPA images as well as the anisotropic magnetoresistance of both Co magnets, revealing a strong impact of multi-domain states on the spin signal.
Mennig, J.; Matthes, F.; Buergler, D. E.; Schneider, C. M. [Peter Gruenberg Institute, Electronic Properties (PGI-6) and Juelich-Aachen Research Alliance, Fundamentals of Future Information Technology (JARA-FIT), Forschungszentrum Juelich GmbH, Juelich D-52425 (Germany)
Dynamic Switching of the Spin Circulation in Tapered Magnetic Nanodisks
Dynamic Switching of the Spin Dynamic Switching of the Spin Circulation in Tapered Magnetic Nanodisks Dynamic Switching of the Spin Circulation in Tapered Magnetic Nanodisks Print Monday, 22 April 2013 12:09 fischer-magnetic vortices Ferromagnetic NiFe disks (500-nm-wide and 20-nm-thick), were fabricated by e-beam lithography onto a waveguide structure. Field pulses, generated by launching current pulses into the waveguide trigger the magnetization dynamics in the elements. Using the soft x-ray microscope XM-1 providing 25-nm spatial resolution, circularly polarized soft x-rays give rise to XMCD contrast which allows to record an image of the in-plane circulation of the magnetic vortex. The topology of vortices-areas where there is a spinning motion around an imaginary axis-is a physical phenomenon which is found across a large
Spin flip probability of electron in a uniform magnetic field
The probability that an electromagnetic wave can flip the spin of an electron is calculated. It is assumed that the electron resides in a uniform magnetic field and interacts with an incoming electromagnetic pulse. The scattering matrix is constructed and the time needed to flip the spin is calculated.
Hammond, Richard T. [Department of Physics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina and Army Research Office, Research Triangle Park, North Carolina 27703 (United States)
Nonlinear spin relaxation in strongly nonequilibrium magnets
A general theory is developed for describing the nonlinear relaxation of spin systems from a strongly nonequilibrium initial state, when, in addition, the sample is coupled to a resonator. Such processes are characterized by nonlinear stochastic differential equations. This makes these strongly nonequilibrium processes principally different from the spin relaxation close to an equilibrium state, which is represented by linear differential equations. The consideration is based on a realistic microscopic Hamiltonian including the Zeeman terms, dipole interactions, exchange interactions, and a single-site anisotropy. The influence of cross correlations between several spin species is investigated. The critically important function of coupling between the spin system and a resonant electric circuit is emphasized. The role of all main relaxation rates is analyzed. The phenomenon of self-organization of transition coherence in spin motion, from the quantum chaotic stage of incoherent fluctuations, is thoroughly described. Local spin fluctuations are found to be the triggering cause for starting the spin relaxation from an incoherent nonequilibrium state. The basic regimes of collective coherent spin relaxation are studied.
V. I. Yukalov
Spin-stabilized magnetic levitation without vertical axis of rotation
The symmetry properties of a magnetic levitation arrangement are exploited to produce spin-stabilized magnetic levitation without aligning the rotational axis of the rotor with the direction of the force of gravity. The rotation of the rotor stabilizes perturbations directed parallel to the rotational axis.
Romero, Louis (Albuquerque, NM); Christenson, Todd (Albuquerque, NM); Aaronson, Gene (Albuquerque, NM)
Comment on Magnetic Monopole Excitations in Spin Ice
It has been proposed recently \\cite{son} that excitations in Spin Ice can be of the form of magnetic monopoles that does not obey the Dirac Quantization Condition. It is also well known \\cite{rj} that the above scenario leads to non-associativity among translation generators. It will be interesting to see how the monopole picture in Spin Ice survives in the light of the latter observation.
Subir Ghosh
Magnetism and spin transport studies on indium tin oxide
MAGNETISM AND SPIN TRANSPORT STUDIES ON INDIUM TIN OXIDE Ali Moraad Hakimi Darwin College University of Cambridge A dissertation submitted for the degree of Doctor of Philosophy at the University of Cambridge February 2011 In loving memory of my... Grandfathers, Cyrus and Peter Abstract This dissertation reports on a detailed systematic study of the investigation into using Indium Oxide based materials in next generation spin-transport electronic ap- plications. Initial studies focused on the optimisation...
Hakimi, Ali Moraad Heydar
Spin-polarized photoelectron spectroscopy has developed into a versatile tool for the study of surface and thin film magnetism. In this chapter, we examine the methodology of the technique and its recent application to a number of different problems. We first examine the photoemission process itself followed by a detailed review of spin-polarization measurement techniques and the related experimental requirements. We review studies of spin polarized surface states, interface states and quantum well states followed by studies of the technologically important oxide systems including half-metallic transition metal oxides, ferromagnet/oxide interfaces and the antiferromagnetic cuprates that exhibit high Tc Superconductivity. We also discuss the application of high-resolution photoemission with spin resolving capabilities to the study of spin dependent self energy effects.
Effects of inelastic spin-dependent electron transport through a spin nanostructure in a magnetic field
The transport properties and current-voltage (I-V) characteristics of a system of spin dimers with antiferromagnetic coupling arranged between metallic contacts are investigated in the tight binding approximation using the Landauer-Buttiker formalism. It is shown that the s-d(f) exchange interaction between the spin moments of the electrons being transported and the spins of the nanostructure leads to the formation of a potential profile as well as its variation due to spin-flip processes. As a result, the spin-dependent transport becomes inelastic, and the transmission coefficient and the I-V characteristic are strongly modified. It is found that the application of a magnetic field induces additional transparency peaks in the spectral characteristic of the system and causes the colossal magnetoresistance effect.
Val'kov, V. V., E-mail: firstname.lastname@example.com; Aksenov, S. V. [Russian Academy of Sciences, Institute of Physics, Siberian Branch (Russian Federation)
Dilute magnetic semiconductors in spin-polarized electronics (invited)
Dilute magnetic semiconductors have proven to be very useful in building an all-semiconductor platform for spintronics{emdash}so far they provide the only viable route to establish spin-polarized current injection into a nonmagnetic semiconductor. The reasons for this become apparent from a simple spin-channel model, which predicts that spin injection into a semiconductor can, within linear response, only readily be achieved from a ferromagnetic injector that has: (i) a resistivity that is comparable to the semiconductor and (ii) preferably is 100% spin polarized. Both of these criteria can be met in magnetic semiconductors, but (so far) are hard to achieve using other materials. Experimentally, we demonstrate how dilute magnetic II{endash}VI semiconductors can be used to inject a strongly (up to 90%) spin-polarized current into a light emitting diode. In addition, we discuss the implications of the spin-channel model for the observation of giant magnetoresistance-like effects in the magnetoresistance of an all-semiconductor device. {copyright} 2001 American Institute of Physics.
Schmidt, Georg; Molenkamp, Laurens W.
A Model for the Behavior of Magnetic Tunnel Junctions
A magnetic tunnel junction is a device that changes its electrical resistance with a change in an applied magnetic field. A typical junction consists of two magnetic electrodes separated by a nonmagnetic insulating layer. The magnetizations of the two electrodes can have two possible extreme configurations, parallel and antiparallel. The antiparallel configuration is observed to have the higher measured resistance and the parallel configuration has the lower resistance. To switch between these two configurations a magnetic field is applied to the device which is primarily used to change the orientation of the magnetization of one electrode usually called the free layer, although with sufficient high magnetic field the orientation of the magnetizations of both of the electrodes can be changed. The most commonly used models for describing and explaining the electronic behavior of tunnel junctions are the Simmons model and the Brinkman model. However, both of these models were designed for simple, spin independent tunneling. The Simmons model does not address the issue of applied magnetic fields nor does it address the form of the electronic band structure in the metallic electrodes, including the important factor of spin polarization. The Brinkman model is similar, the main difference between the two models being the shape of the tunneling barrier potential between the two electrodes. Therefore, the research conducted in this thesis has developed a new theoretical model that addresses these important issues starting from basic principles. The main features of the new model include: the development of equations for true spin dependent tunneling through the insulating barrier, the differences in the orientations of the electrode magnetizations on either side of the barrier, and the effects of the density of states function on the behavior of the junction. The present work has explored densities of states that are more realistic than the simplified free electron density of states function, and has developed an exact analytic solution for the case of an electron band of finite width. The approach taken in this thesis easily allows extension to cases where the band structure is different on either side of the barrier (known as heterojunctions) which are of greater interest in real magnetic tunnel junction devices rather than the simple, identical band structure devices.
Bryan John Baker
Fully relativistic calculation of nuclear magnetic shieldings and indirect nuclear spin-spin couplings in group-15 and -16 hydrides
Fully relativistic calculations of the isotropic and anisotropic parts of both indirect nuclear spin�spin couplings 1 J(X- H ) and 2 J( H-H ) and nuclear magnetic shieldings ?(X) and ?(H) for the group-15 and -16 hydrides are presented. Relativistic calculations were performed with Dirac�Fock wave functions and the random phase approximation method. Results are compared to its nonrelativistic counterpart. Paramagnetic and diamagnetic contributions to the nuclear magnetic shielding constants are also reported. We found very large relativistic corrections to both properties in the sixth-row hydrides ( BiH 3 and PoH 2 ). Our calculations of the relativistic corrections to the isotropic part of ? at the heavy nucleus X show that it is roughly proportional to Z 3.2 in both series of molecules. Paramagnetic term ? p is more sensitive to the effects of relativity than the diamagnetic one ? d even though both have a behavior proportional to third power of the nuclear charge Z.
Sergio S. Gomez; Rodolfo H. Romero; Gustavo A. Aucar
Charge and Spin Transport in Dilute Magnetic Semiconductors
This proposal to the DOE outlines a three-year plan of research in theoretical and computational condensed-matter physics, with the aim of developing a microscopic theory for charge and spin dynamics in disordered materials with magnetic impurities. Important representatives of this class of materials are the dilute magnetic semiconductors (DMS), which have attracted great attention as a promising basis for spintronics devices. There is an intense experimental effort underway to study the transport properties of ferromagnetic DMS such as (Ga,Mn)As, and a number of interesting features have emerged: negative magnetoresistance, anomalous Hall effect, non-Drude dynamical conductivity, and resistivity maxima at the Curie temperature. Available theories have been able to account for some of these features, but at present we are still far away from a systematic microscopic understanding of transport in DMS. We propose to address this challenge by developing a theory of charge and spin dynamics based on a combination of the memory-function formalism and time-dependent density functional theory. This approach will be capable of dealing with two important issues: (a) the strong degree of correlated disorder in DMS, close to the localization transition (which invalidates the usual relaxation-time approximation to the Boltzmann equation), (b) the essentially unknown role of dynamical many-body effects such as spin Coulomb drag. We will calculate static and dynamical conductivities in DMS as functions of magnetic order and carrier density, which will advance our understanding of recent transport and infrared absorption measurements. Furthermore, we will study collective plasmon excitations in DMS (3D, 2D and quantum wells), whose linewidths could constitute a new experimental probe of the correlation of disorder, many-body effects and charge and spin dynamics in these materials.
Ullrich, Carsten A.
Spin glass transition in a magnetic field: a renormalization group study
We study the transition of short range Ising spin glasses in a magnetic field, within a general replica symmetric field theory, which contains three masses and eight cubic couplings, that is defined in terms of the fields representing the replicon, anomalous and longitudinal modes. We discuss the symmetry of the theory in the limit of replica number n ? 0, and consider the regular case where the longitudinal and anomalous masses remain degenerate. The spin glass transitions in zero and non-zero field are analyzed in a common framework. The mean field treatment shows the usual results, that is a transition in zero field, where all the modes become critical, and a transition in nonzero field, at the de Almeida-Thouless (AT) line, with only the replicon mode critical. Renormalization group methods are used to study the critical behavior, to order ? = 6 ? d. In the general theory we find a stable fixed-point associated to the spin glass transition in zero field. This fixed-point becomes unstable in the presence of a small magnetic field, and we calculate crossover exponents, which we relate to zero-field critical exponents. In a finite magnetic field, we find no physical stable fixed-point to describe the AT transition, in agreement with previous results of other authors. PACS numbers: 75.50.Lk, 75.40.Cx 1 I
I. R. Pimentel; T. Temesv�ri; C. De Dominicis
Bias-tunable electron-spin polarization in an antiparallel double ?-magnetic-barrier nanostructure
We present a theoretical study of spin-dependent electron transport in an antiparallel double @d-magnetic-barrier nanostructure with an applied bias. It is shown that large spin-polarized current can be achieved in such a device with unidentical strength ... Keywords: 72.25.-b, 73.23.-b, 73.40.Gk, 75.75.+a, Magnetic quantum structure, Spin filtering, Spin polarization, Spintronics
Mao-Wang Lu; Gui-Lian Zhang; Yong-Hong Kong
Direct observation of dynamics of single spinning dust grains in weakly magnetized complex plasma
The rotational dynamics of single dust grains in a weak magnetic field is investigated on a kinetic level. Experiments reveal spin-up of spherical dust grains and alignment of their magnetic moments parallel to the magnetic induction vector. The angular velocity of spinning prolate grains varies as magnetic induction increases to 250 G. Spinning dust grains are found to flip over only when the magnetic field magnitude is changing. The results demonstrate that dusty plasma has paramagnetic properties. Qualitative interpretations are proposed to explain newly discovered phenomena.
Dzlieva, E. S.; Karasev, V. Yu., E-mail: firstname.lastname@example.com [St. Petersburg State University, Institute of Physics (Russian Federation); Petrov, O. F. [Russian Academy of Sciences, Institute for High Energy Densities, Joint Institute for High Temperatures (Russian Federation)
Magnetic Phase Transition and Spin Wave Excitations in the ...
... An energy scan through the spin wave excitations ... The intensity above TC comes from paramagnetic spin ... quickly move to higher energies and out ...
Spinning a New Type of Magnetic Field | U.S. DOE Office of Science (SC)
Spinning a New Type of Magnetic Field Spinning a New Type of Magnetic Field Basic Energy Sciences (BES) BES Home About Research Facilities Science Highlights Benefits of BES Funding Opportunities Basic Energy Sciences Advisory Committee (BESAC) News & Resources Contact Information Basic Energy Sciences U.S. Department of Energy SC-22/Germantown Building 1000 Independence Ave., SW Washington, DC 20585 P: (301) 903-3081 F: (301) 903-6594 E: email@example.com More Information » October 2013 Spinning a New Type of Magnetic Field Harnessing the spins of electrons in a new way - enabling efficient magnetic switching and holding promise for spintronic devices. Print Text Size: A A A Subscribe FeedbackShare Page Click to enlarge photo. Enlarge Photo Image courtesy of John Xiao Schematic of mechanism for generating a magnetic field. The system consists
Magnetic soft x-ray microscopy-imaging fast spin dynamics inmagnetic nanostructures
Magnetic soft X-ray microscopy combines 15nm spatial resolution with 70ps time resolution and elemental sensitivity. Fresnel zone plates are used as X-ray optics and X-ray magnetic circular dichroism serves as magnetic contrast mechanism. Thus scientifically interesting and technologically relevant low dimensional nanomagnetic systems can be imaged at fundamental length and ultrafast time scales in a unique way. Studies include magnetization reversal in magnetic multilayers, nanopatterned systems, vortex dynamics in nanoelements and spin current induced phenomena.
Fischer, Peter; Kim, Dong-Hyun; Mesler, Brooke L.; Chao, Weilun; Sakdinawat, Anne E.; Anderson, Erik H.
Coherent spin control by electrical manipulation of the magnetic anisotropy
High-spin paramagnetic manganese defects in polar piezoelectric zinc oxide exhibit a simple almost axial anisotropy and phase coherence times of the order of a millisecond at low temperatures. The anisotropy energy is tunable using an externally applied electric field. This can be used to control electrically the phase of spin superpositions and to drive spin transitions with resonant microwave electric fields.
Richard E George; James P Edwards; Arzhang Ardavan
Ferrofluid spin-up flows from uniform and non-uniform rotating magnetic fields
When ferrofluid in a cylindrical container is subjected to a rotating azimuthally directed magnetic field, the fluid "spins up" into an almost rigid-body rotation where ferrofluid nanoparticles have both a linear and an ...
Khushrushahi, Shahriar Rohinton
Classical relativistic model for spin dependence in a magnetized electron gas
The response of a cold electron gas is generalized to include the spin of the electron described by the relativistically correct quasiclassical Bargmann-Michel-Telegdi (BMT) equation. The magnetization of the electron gas is assumed to be along the background magnetic field B and the spin-dependent contribution to the response tensor is proportional to the magnitude of the magnetization. The dispersion equation is shown to be quadratic in the refractive index squared, and dispersion curves for the two wave modes are plotted for cases where the magnetic field associated with magnetization is comparable with B. Two intrinsically spin-dependent wave modes are identified: one bounded by two resonances and the other by two cutoffs. The counterpart of the z mode can escape without encountering a resonance or a cutoff.
Melrose, D. B. [School of Physics, University of Sydney, NSW 2006 (Australia); Mushtaq, A. [School of Physics, University of Sydney, NSW 2006 (Australia); TPPD, PINSTECH, P. O. Nilore Islamabad 44000 (Pakistan)
Quantum spins mimic refrigerator magnets | Argonne National Laboratory
but also the spin of electrons. This approach is known within scientific circles as "spintronics." One of the significant hurdles to future spintronic devices is finding ways to...
Synchronization of an array of spin torque nano oscillators in periodic applied external magnetic field
Considering an array of spin torque transfer nano oscillators (STNOs), we have investigated the synchronization property of the system under the action of a common periodically driven applied external magnetic field by numerically analyzing the underlying system of Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equations for the macro-spin variables. We find the novel result that the applied external magnetic field can act as a medium to induce synchronization of periodic oscillations, both in-phase and anti-phase, even without coupling through spin current, thereby leading to the exciting possibility of enhancement of microwave power in a straightforward way.
B. Subash; V. K. Chandrasekar; M. Lakshmanan
Dynamic Phase Transitions In The Spin-2 Ising System Under An Oscillating Magnetic Field Within The Effective-Field Theory
The dynamic phase transitions are studied in the spin-2 Ising model under a time-dependent oscillating magnetic field by using the effective-field theory with correlations. The effective-field dynamic equation is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first- or second-order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic order parameter and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are presented in (T/zJ, h/zJ) plane.
Ertas, Mehmet; Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey)
Nanoscale magnetic field mapping with a single spin scanning probe magnetometer
We demonstrate quantitative magnetic field mapping with nanoscale resolution, by applying a lock-in technique on the electron spin resonance frequency of a single nitrogen-vacancy defect placed at the apex of an atomic force microscope tip. In addition, we report an all-optical magnetic imaging technique which is sensitive to large off-axis magnetic fields, thus extending the operation range of diamond-based magnetometry. Both techniques are illustrated by using a magnetic hard disk as a test sample. Owing to the non-perturbing and quantitative nature of the magnetic probe, this work should open up numerous perspectives in nanomagnetism and spintronics.
Rondin, L.; Tetienne, J.-P.; Spinicelli, P.; Roch, J.-F.; Jacques, V. [Laboratoire de Photonique Quantique et Moleculaire, Ecole Normale Superieure de Cachan and CNRS UMR 8537, 94235 Cachan Cedex (France); Dal Savio, C.; Karrai, K. [Attocube systems AG, Koeniginstrasse 11A RGB, Munich 80539 (Germany); Dantelle, G. [Laboratoire de Physique de la Matiere Condensee, Ecole Polytechnique and CNRS UMR 7643, 91128 Palaiseau (France); Thiaville, A.; Rohart, S. [Laboratoire de Physique des Solides, Universite Paris-Sud and CNRS UMR 8502, 91405 Orsay (France)
Spin polarization and magnetic dichroism in core-level photoemission from ferromagnets
In this thesis we present a theoretical investigation of angle- and spin-resolved core-level photoemission from ferromagnetic Fe and Ni. We also consider magneto-dichroic effects due to reversal of the photon helicity or reversal of the sample magnetization direction. In chapter 1, we provide a brief outline of the history of photoemission, and show how it has played an important role in the development of modern physics. We then review the basic elements of the theory of core-level photoemission, and discuss the validity of the some of the commonly-used approximations. In chapter 2, we present a one-electron theory to calculate spin- and angle-resolved photoemission spectra for an arbitrary photon polarization. The Hamiltonian includes both spin-orbit and exchange interactions. As test cases for the theory, we calculate the spin polarization and magnetic dichroism for the Fe 2p core level, and find that agreement with experiment is very good.
Menchero, J.G. [Univ. of California, Berkeley, CA (United States). Dept. of Physics]|[Lawrence Berkeley National Lab., CA (United States)
Nuclear-electronic spin systems, magnetic resonance, and quantum information processing
A promising platform for quantum information processing is that of silicon impurities, where the quantum states are manipulated by magnetic resonance. Such systems, in abstraction, can be considered as a nucleus of arbitrary spin coupled to an electron of spin one-half via an isotropic hyperfine interaction. We therefore refer to them as "nuclear-electronic spin systems". The traditional example, being subject to intensive experimental studies, is that of phosphorus doped silicon (Si:P) which couples a spin one-half electron to a nucleus of the same spin, with a hyperfine strength of 117.5 MHz. More recently, bismuth doped silicon (Si:Bi) has been suggested as an alternative instantiation of nuclear-electronic spin systems, differing from Si:P by its larger nuclear spin and hyperfine strength of 9/2 and 1.4754 GHz respectively. The aim of this thesis has been to develop a model that is capable of predicting the magnetic resonance properties of nuclear-electronic spin systems. The theoretical predictions of this model have been tested against experimental data collected on Si:Bi at 4.044 GHz, and have proven quite successful. Furthermore, the larger nuclear spin and hyperfine strength of Si:Bi, compared with that of Si:P, are predicted to offer advantages for quantum information processing. Most notable amongst these is that magnetic field-dependent two-dimensional decoherence free subspaces, called optimal working points, have been identified to exist in Si:Bi, but not Si:P.
M. H. Mohammady
Magnetism reflectometer study shows LiF layers improve efficiency in spin valve devices
New, more efficient materials for spin valves - a device used in magnetic sensors, random access memories, and hard disk drives - may be on the way based on research using the magnetism reflectometer at Oak Ridge National Laboratory (ORNL). Spin valve devices work by means of two or more conducting magnetic material layers that alternate their electrical resistance depending on the layers alignment. Giant magnetoresistance is a quantum mechanical effect first observed in thin film structures about 20 years ago. The effect is observed as a significant change in electrical resistance, depending on whether the magnetization of adjacent ferromagnetic layers is in a parallel or an antiparallel magnetic alignment. 'What we are doing here is developing new materials. The search for new materials suitable for injecting and transferring carriers with a preferential spin orientation is most important for the development of spintronics,' said Valeria Lauter, lead instrument scientist on the magnetism reflectometer at the Spallation Neutron Source (SNS), who collaborated on the experiment. The researchers discovered that the conductivity of such materials is improved when an organic polymer semiconductor layer is placed between the magnetic materials. Organic semiconductors are now the material of choice for future spin valve devices because they preserve spin coherence over longer times and distances than conventional semiconductors. While research into spin valves has been ongoing, research into organic semiconductors is recent. Previous research has shown that a 'conductivity mismatch' exists in spin valve systems in which ferromagnetic metal electrodes interface with such organic semiconductors as Alq3 ({pi}-conjugated molecule tris(8-hydroxy-quinoline) aluminium). This mismatch limits the efficient injection of the electrons from the electrodes at the interface with the semiconductor material. However, lithium fluoride (LiF), commonly used in light-emitting diodes, has been found to enhance the injection of electrons through the semiconductor. Researchers from the University of Alabama and ORNL used polarized neutrons at the magnetism reflectometer at SNS to investigate the electronic, magnetic, and structural properties of the electrodes in a novel system. In this system, the magnetic layers cobalt and Ni{sub 80}Fe{sub 20} are interfaced with spacer layers composed of the organic semiconductor Alq3. A coupling layer of LiF is inserted to separate the magnetized layers from the semiconductor. 'ALQ3 is an organic semiconductor material,' said Lauter. 'Normally in these systems a first magnetic layer is grown on a hard substrate so that one can get the controlled magnetic parameters. Then you grow the organic semiconductor layer, followed by another magnetic material layer, such as cobalt.' In addition to determining the effect of the LiF layers on the efficiency of the electron injection, the researchers wanted to determine the magnetic properties of the cobalt and Ni{sub 80}Fe{sub 20} as well as the interfacial properties: whether there is interdiffusion of cobalt through the LiF layer to the semiconductor, for example. The researchers used polarized neutrons at beam line 4A to probe the entire, layer-by-layer assembly of the system. 'Reflectometry with polarized neutrons is a perfect method to study thin magnetic films,' Lauter said. 'These thin films - if you put one on a substrate, you see it just like a mirror. However, this mirror has a very complicated internal multilayer structure. The neutrons look inside this complicated structure and characterize each and every interface. Due to the depth sensitivity of the method, we measure the structural and magnetic properties of each layer with the resolution of 0.5 nm. The neutron scattering results found that inserting LiF as a barrier significantly improves the quality of the interface, increasing the injection of electrons from the magnetic layer through the organic semiconductor in the spin valve and enhancing the overall properties of the system. In related work the magneti
Bardoel, Agatha A [ORNL; Lauter, Valeria [ORNL; Szulczewski, Greg J [ORNL
Three-dimensional finite element modeling of a magnet array spinning above a conductor
DOE Green Energy (OSTI)
Drag forces due to eddy currents induced by the relative motion of a conductor and a magnetic field occur in many practical devices: motors, brakes, magnetic bearings, and magnetically levitated vehicles. Recently, finite element codes have included solvers for 3-D eddy current geometries and have the potential to be very useful in the design and analysis of these devices. In this paper, numerical results from three-dimensional modeling of a magnet array spinning above a conductor are compared to experimental results in order to assess the capabilities of these codes.
Lorimer, W.L.; Lieu, D.K. [Univ. of California, Berkeley, CA (United States). Dept. of Mechanical Engineering; Hull, J.R.; Mulcahy, T.M.; Rossing, T.D. [Argonne National Lab., IL (United States)
Superfluid-Mott Insulator Transition of Spin-2 Cold Bosons in an Optical Lattice in a Magnetic Field
The superfluid-Mott insulator transition of spin-2 boson atoms with repulsive interaction in an optical lattice in a magnetic field is presented. By using the mean field theory, Mott ground states and phase diagrams of superfluid-Mott insulator transition at zero temperature are revealed. Applied magnetic field leads to some phase boundaries splitting. For all the initial Mott ground states containing multiple spin components, different spin components take on different phase boundaries. It is found that in this system the phase boundaries with different magnetization can be moved in different ways by only changing the intensity of the applied magnetic field.
Shuo Jin; Jing-Min Hou; Bing-Hao Xie; Li-Jun Tian; Mo-Lin Ge
Spin-polarized current oscillations in diluted magnetic semiconductor multiple quantum wells Manuel Bejar,1
Spin-polarized current oscillations in diluted magnetic semiconductor multiple quantum wells Manuel and charge dynamics of electrons in n-doped II-VI semiconductor multiple quantum wells when one or more quantum wells are doped with Mn. The interplay between strongly nonlinear interwell charge transport
Sánchez, David
Spin flip loss in magnetic storage of ultracold neutrons
We analyze the depolarization of ultracold neutrons confined in a magnetic field configuration similar to those used in existing or proposed magneto-gravitational storage experiments aiming at a precise measurement of the neutron lifetime. We use an approximate quantum mechanical analysis such as pioneered by Walstrom \\emph{et al} [Nucl. Instrum. Methods Phys. Res. A 599, 82 (2009)]. Our analysis is not restricted to purely vertical modes of neutron motion. The lateral motion is shown to cause the predominant depolarization loss in a magnetic storage trap.
A. Steyerl; C. Kaufman; G. M�ller; S. S. Malik; A. M. Desai
Ni spin switching induced by magnetic frustration in FeMn/Ni/Cu(001)
Epitaxially grown FeMn/Ni/Cu(001) films are investigated by Photoemission Electron Microscopy and Magneto-Optic Kerr Effect. We find that as the FeMn overlayer changes from paramagnetic to antiferromagnetic state, it could switch the ferromagnetic Ni spin direction from out-of-plane to in-plane direction of the film. This phenomenon reveals a new mechanism of creating magnetic anisotropy and is attributed to the out-of-plane spin frustration at the FeMn-Ni interface.
Wu, J.; Choi, J.; Scholl, A.; Doran, A.; Arenholz, E.; Hwang, Chanyong; Qiu, Z. Q.
Coherent Spin Manipulations of a Polarized Beam With a Localized RF Magnetic Field
The coherent manipulation of spin observables in storage rings provides opportunities to test the application of some fundamental dynamical principles. In this context, it is possible to confirm, using gauge invariance and Lorentz invariance, a conjecture framed by A. M. Kondratenko concerning the "natural" or "intrinsic" resonance strength applicable to a spin rotation from a controlled Froissart-Stora sweep with an RF dipole magnet. The discussion includes a brief treatment of the "forced" component of the resonance strength associated with the effect of the betatron oscillations induced by the operation of the RF diple and a discussion of the effective resonance strength as a function of betatron tunes.
Dennis Sivers
High-pressure Magic Angle Spinning Nuclear Magnetic Resonance
A high-pressure magic angle spinning (MAS) NMR capability, consisting of a reusable high-pressure MAS rotor, a high-pressure loading/reaction chamber for in situ sealing and re-opening of the high-pressure MAS rotor, and a MAS probe with a localized RF coil for background signal suppression, is reported. The unusual technical challenges associated with development of a reusable high-pressure MAS rotor are addressed in part by modifying standard ceramics for the rotor sleeve to include micro-groves at the internal surface at both ends of the cylinder. In this way, not only is the advantage of ceramic cylinders for withstanding very high-pressure utilized, but also plastic bushings can be glued tightly in place so that other plastic sealing mechanisms/components and O-rings can be mounted to create the desired high-pressure seal. Using this strategy, sealed internal pressures exceeding 150 bars have been achieved and sustained under ambient external pressure with minimal penetration loss of pressure for 72 hours. As an application example, in situ 13C MAS NMR studies of mineral carbonation reaction intermediates and final products of forsterite (Mg2SiO4) reacted with supercritical CO2 and H2O at 150 bar and 50?C are reported, with relevance to geological sequestration of carbon dioxide.
Hoyt, David W.; Turcu, Romulus VF; Sears, Jesse A.; Rosso, Kevin M.; Burton, Sarah D.; Felmy, Andrew R.; Hu, Jian Z.
Calculation of the expectation values of the spin and the magnetic moment of the gamma photons created as a result of the electron-positron annihilation
We have calculated the expectation values of the spin and the intrinsic magnetic moment of the gamma photons created as a result of the electron-positron annihilation. We show that, depending on its helicity a gamma photon propagating in z direction with an angular frequency carries a magnetic moment of along the propagation direction. Here the (+) and (-) signs stand for the right hand and left circular helicity respectively. We also show that whatever the helicity is, the spin of each gamma photon is equal to zero (but not !). We argue that in a Stern-Gerlach experiment (SGE) the magnetic moment is an important property but not the spin of the particles. Because of these two symmetric values of the magnetic moment, we expect a splitting of the gamma photon beam into two symmetric subbeams in a (SGE). We believe that the present result will be helpful for understanding the recent attempts on the (SGE) with slow light and the behavior of the dark polaritons and also the atomic spinor polaritons.
Saglam, Mesude
Effect of Electric and Magnetic Fields on Spin Dynamics in the Resonant Electric Dipole Moment Experiment
A buildup of the vertical polarization in the resonant electric dipole moment (EDM) experiment [Y. F. Orlov, W. M. Morse, and Y. K. Semertzidis, Phys. Rev. Lett. 96, 214802 (2006)] is affected by a horizontal electric field in the particle rest frame oscillating at a resonant frequency. This field is defined by the Lorentz transformation of an oscillating longitudinal electric field and a uniform vertical magnetic one. The effect of a longitudinal electric field is significant, while the contribution from a magnetic field caused by forced coherent longitudinal oscillations of particles is dominant. The effect of electric field on the spin dynamics was not taken into account in previous calculations. This effect is considerable and leads to decreasing the EDM effect for the deuteron and increasing it for the proton. The formula for resonance strengths in the EDM experiment has been derived. The spin dynamics has been calculated.
Alexander J. Silenko
Single-spin measurements for quantum computation using magnetic resonance force microscopy
The quantum theory of a singlespin measurements using a magnetic resonance force microscopy is presented. We use an oscillating cantilever-driven adiabatic reversals technique. The frequency shift of the cantilever vibrations is estimated. We show that the frequency shift causes the formation of the Schroedinger cat state for the cantilever. The interaction between the cantilever and the environment quickly destroys the coherence between the two cantilever trajectories. It is shown that using partial adiabatic reversals one can obtain a significant increase in the frequency shift. We discuss the possibility of sub-magneton spin density detection in molecules using magnetic resonance force microscopy.
Berman, G. P. (Gennady P.); Borgonovi, F.; Rinkevicius, Z.; Tsifrinovich, V. I. (Vladimir I.)
Probing Spin Liquids with a New Pulsed-Magnet System | Advanced Photon
a Magnetic Moment in a Split Picosecond a Magnetic Moment in a Split Picosecond Unpeeling Atoms and Molecules from the Inside Out Butterfly Wing Yields Clues to Light-Altering Structures Squeezing Information from Materials under Extreme Pressure Quick-Change Molecules Caught in the Act Science Highlights Archives: 2013 | 2012 | 2011 | 2010 2009 | 2008 | 2007 | 2006 2005 | 2004 | 2003 | 2002 2001 | 2000 | 1998 | Subscribe to APS Science Highlights rss feed Probing Spin Liquids with a New Pulsed-Magnet System AUGUST 26, 2010 Bookmark and Share The (008) intensity color map on a θ vs. 2θ mesh. With increasing magnetic field the peak splits at a critical field of H ~29 T, which is a hallmark of a structural phase transition with a reduction from cubic to tetragonal or orthorhombic symmetry. Above the critical field,
Magnetic ordering in tetragonal FeS: Evidence for strong itinerant spin fluctuations
Mackinawite is a naturally occurring layer-type FeS mineral important in biogeochemical cycles and, more recently, in the development of microbial fuel cells. Conflicting results have been published as to the magnetic properties of this mineral, with Moessbauer spectroscopy indicating no magnetic ordering down to 4.2 K but density functional theory (DFT) predicting an antiferromagnetic ground state, similar to the Fe-based high-temperature superconductors with which it is isostructural and for which it is known that magnetism is suppressed by strong itinerant spin fluctuations. We investigated this latter possibility for mackinawite using photoemission spectroscopy, near-edge x-ray absorption fine structure spectroscopy, and DFT computations. Our Fe 3{sub s} core-level photoemission spectrum of mackinawite showed a clear exchange-energy splitting (2.9 eV) consistent with a 1 {micro}{sub B} magnetic moment on the Fe ions, while the Fe L-edge x-ray absorption spectrum indicated rather delocalized Fe 3{sub d} electrons in mackinawite similar to those in Fe metal. Our DFT computations demonstrated that the ground state of mackinawite is single-stripe antiferromagnetic, with an Fe magnetic moment (2.7 {micro}{sub B}) that is significantly larger than the experimental estimate and has a strong dependence on the S height and lattice parameters. All of these trends signal the existence of strong itinerant spin fluctuations. If spin fluctuations prove to be mediators of electron pairing, we conjecture that mackinawite may be one of the simplest Fe-based superconductors.
Kwon, K.D.; Refson, K.; Bone, S.; Qiao, R.; Yang, W.; Liu, Z.; Sposito, G.
Rotor Design for High Pressure Magic Angle Spinning Nuclear Magnetic Resonance
High pressure magic angle spinning (MAS) nuclear magnetic resonance (NMR) with a sample spinning rate exceeding 2.1 kHz and pressure greater than 165 bar has never been realized. In this work, a new sample cell design is reported, suitable for constructing cells of different sizes. Using a 7.5 mm high pressure MAS rotor as an example, internal pressure as high as 200 bar at a sample spinning rate of 6 kHz is achieved. The new high pressure MAS rotor is re-usable and compatible with most commercial NMR set-ups, exhibiting low 1H and 13C NMR background and offering maximal NMR sensitivity. As an example of its many possible applications, this new capability is applied to determine reaction products associated with the carbonation reaction of a natural mineral, antigorite ((Mg,Fe2+)3Si2O5(OH)4), in contact with liquid water in water-saturated supercritical CO2 (scCO2) at 150 bar and 50 ?C. This mineral is relevant to the deep geologic disposal of CO2, but its iron content results in too many sample spinning sidebands at low spinning rate. Hence, this chemical system is a good case study to demonstrate the utility of the higher sample spinning rates that can be achieved by our new rotor design. We expect this new capability will be useful for exploring solid-state, including interfacial, chemistry at new levels of high-pressure in a wide variety of fields.
Turcu, Romulus VF; Hoyt, David W.; Rosso, Kevin M.; Sears, Jesse A.; Loring, John S.; Felmy, Andrew R.; Hu, Jian Z.
Cyanide clusters of ReII with 3d metal ions and their magnetic properties: incorporating anisotropic ions into metal-cyanide clusters with high spin magnetic ground states
Clusters of metal ions that possess large numbers of magnetically coupled unpaired electrons have attracted much interest in recent years due to their fascinating magnetic behavior. With an appreciable component of magnetic anisotropy, these large-spin paramagnetic molecules can exhibit an energy barrier to inversion of their magnetic dipole, leading to spontaneous magnetization and magnetic hysteresis below a critical temperature. Since this behavior is a property of an individual clusters rather than a collection of molecules, this phenomenon has been dubbed ??Single Molecule Magnetism??. Our approach to the study of new high-spin systems has been to exert a measure of synthetic control in the preparation of clusters. Specifically we are employing highly anisotropic metal ions with the anticipation that these ions would engender large overall magnetic anisotropy in the resulting clusters. The first step in this process was the development of the chemistry of two new d5 ReII (S = ??) complexes, namely [ReII(triphos)(CH3CN)3][PF6]2 and [Et4N][ReII(triphos)(CN)3]. The magnetic, optical and electrochemical properties were studied and theoretical models were developed to describe the origin of the large temperature independent paramagnetism that was observed. Next, we successfully employed transition metal cyanide chemistry using the ReII building blocks to prepare a family of isostructural, cubic clusters of the general formula {[MCl]4[Re(triphos)(CN)3]4} M = Mn, Fe, Co, Ni, Cu, Zn whose 3d ions adopt local tetrahedral geometries. Within the clusters, magnetic exchange is observed between the paramagnetic ions, which has been modeled using an Ising exchange model to account for the dominating anisotropy of the ReII ion. Despite the high pseudo-symmetry of the clusters (Td), this work has yielded a rare example of a metal-cyanide single molecule magnet, {[MCl]4[Re(triphos)(CN)3]4} with an S = 8 ground state, D = -0.39 cm-1 and an effective energy barrier for magnetization reversal of Ueff = 8.8 cm-1. The elucidation of this family of isostructural clusters has also allowed us to pursue fundamental work on the structure/property relationships of the exotic, paramagnetic ReII ion. As the clusters are soluble, stable compounds, the future of this chemistry lies in the development of a true building-block approach to ??super-clusters?? that exhibit very high ground state spin values.
Schelter, Eric John
Identification and selection rules of the spin-wave eigen-modes in a normally magnetized nano-pillar
Identification and selection rules of the spin-wave eigen-modes in a normally magnetized nano nano-pillar (Permalloy-Copper-Permalloy) by means of a Magnetic Resonance Force Microscope (MRFM). We azimuthal index = 0, the RF cur- rent flowing through the nano-pillar, creating a circular RF Oersted field
Spin Asymmetries Arising In Neutrino-Lepton Processes In A Magnetic Field And Their Macroscopic Appearance
We present expressions that determine the differential cross sections and energy and momentum losses for the neutrino-lepton processes {nu}le- {yields} {nu}le-, {nu}-tildele- {yields} {nu}-tildele-, {nu}l{nu}-tildel {yields} e-e+, {nu}l{nu}-tildee {yields} l-e+, {nu}le- {yields} {nu}el- in a magnetic field with allowance for the longitudinal and transverse polarizations of the charged leptons and antileptons and the results on the spin asymmetries arising in these processes.
Huseynov, Vali A. [Department of General and Theoretical Physics, Nakhchivan State University, AZ 7000, Nakhchivan (Azerbaijan); Laboratory of Physical Research, Nakhchivan Division of Azerbaijan National Academy of Sciences, AZ 7000, Nakhchivan (Azerbaijan); Gasimova, Rasmiyya E.; Akbarova, Nurida Y.; Hajiyeva, Billura T. [Department of General and Theoretical Physics, Nakhchivan State University, AZ 7000, Nakhchivan (Azerbaijan)
Group velocity of extraordinary waves in superdense magnetized quantum plasma with spin-1/2 effects
Based on the one component plasma model, a new dispersion relation and group velocity of elliptically polarized extraordinary electromagnetic waves in a superdense quantum magnetoplasma are derived. The group velocity of the extraordinary wave is modified due to the quantum forces and magnetization effects within a certain range of wave numbers. It means that the quantum spin-1/2 effects can reduce the transport of energy in such quantum plasma systems. Our work should be of relevance for the dense astrophysical environments and the condensed matter physics.
Li Chunhua; Ren Haijun; Yang Weihong [Department of Modern Physics, University of Science and Technology of China, 230026 Hefei (China); Wu Zhengwei [Department of Modern Physics, University of Science and Technology of China, 230026 Hefei (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong); Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong)
Non-Uniform Switching of the Perpendicular Magnetization in a Spin-Torque Magnetic Nanopillar
Time-resolved scanning transmission x-ray microscopy (STXM) measurements were performed to study the current-induced magnetization switching mechanism in nanopillars exhibiting strong perpendicular magnetic anisotropy (PMA). This technique provides both short time (70 ps) and high spatial (25 nm) resolution. Direct imaging of the magnetization demonstrates that, after an incubation time of {approx} 1.3 ns, a 100 x 300 nm{sup 2} ellipsoidal device switches in {approx} 1 ns via a central domain nucleation and opposite propagation of two domain walls towards the edges. High domain wall velocities on the order of 100m/s are measured. Micromagnetic simulations are shown to be in good agreement with experimental results and provide insight into magnetization dynamics during the incubation and reversal period.
Bernstein, David
Spin-polarized relativistic linear-muffin-tin-orbital method: Volume-dependent electronic structure and magnetic moment of plutonium
The linear-muffin-tin-orbital method is generalized to the case of relativistic and spin-polarized self-consistent band calculations. Our formalism is analogous to the standard orthogonal--linear-muffin-tin-orbital formalism, except that the potential functions and the potential parameters are now matrices. The method is used to perform density-functional calculations for fcc plutonium with different atomic volumes. The formation of spin and orbital magnetic moments, as well as the changes in the energy bands for volume changes corresponding to the {alpha}-{delta} transition, are investigated. The calculated magnetic moments agree quite well with the experimental ones.
Solovyev, I.V. (Institute of Chemistry, Ural Branch of U.S.S.R. Academy of Science, Sverdlovsk GSP-145, U.S.S.R. (SU)); Liechtenstein, A.I. (Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-7000 Stuttgart 80, Federal Republic of Germany (DE)); Gubanov, V.A. (Institute of Chemistry, Ural Branch of U.S.S.R. Academy of Science, Sverdlovsk GSP-145, U.S.S.R. (SU)); Antropov, V.P. (Institute of Metal Physics, Ural Branch of U.S.S.R. Academy of Science, Sverdlosk GSP-145, U.S.S.R. (SU)); Andersen, O.K. (Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-7000 Stuttgart 80, Federal Republic of Germany (DE))
Spin relaxation and linear-in-electric-field frequency shift in an arbitrary, time-independent magnetic field
A method is presented to calculate the spin relaxation times T{sub 1}, T{sub 2} due to a nonuniform magnetic field, and the linear-in-electric-field precession frequency shift {delta}{omega}{sub E} when an electric field is present, in the diffusion approximation for spins confined to a rectangular cell. It is found that the rectangular cell geometry admits of a general result for T{sub 1}, T{sub 2}, and {delta}{omega}{sub E} in terms of the spatial cosine-transform components of the magnetic field.
Clayton, Steven Michael [Los Alamos National Laboratory
Spin flip of neutrinos with magnetic moment in core-collapse supernova
Neutrinos with magnetic moment experience chirality flips while scattering off charged particles. It is known that if neutrino is a Dirac fermion, then such chirality flips lead to the production of sterile right-handed neutrinos inside the core of a star during the stellar collapse, which may facilitate the supernova explosion and modify the supernova neutrino signal. In the present paper we reexamine the production of right-handed neutrinos during the collapse using a dynamical model of the collapse. We refine the estimates of the values of the Dirac magnetic moment which are necessary to substantially alter the supernova dynamics and neutrno signal. It is argued in particular that Super-Kamiokande will be sensitive at least to {mu}{sub {nu}Dirac} = 10{sup -13{mu}}{sub B} in case of a galactic supernova explosion. Also we briefly discuss the case of Majorana neutrino magnetic moment. It is pointed out that in the inner supernova core spin flips may quickly equilibrate electron neutrinos with nonelectron antineutrinos if {mu}{sub {nu}Majorana} {>=} 10{sup -12{mu}}{sub B}. This may lead to various consequences for supernova physics.
Lychkovskiy, O. V., E-mail: firstname.lastname@example.com; Blinnikov, S. I. [Institute for Theoretical and Experimental Physics (Russian Federation)
Magnetism Highlights| Neutron Science | ORNL
Magnetism Magnetism SHARE Magnetism Highlights 1-5 of 5 Results ARCS maps collaborative magnetic spin behavior in iron telluride December 01, 2011 - Researchers have long thought that magnetism and superconductivity are mutually exclusive. The former typically involves localized atomic electrons. The latter requires freely propagating, itinerant electrons. Unexpected Magnetic Excitations in Doped Insulator Surprise Researchers October 01, 2011 - When doping a disordered magnetic insulator material with atoms of a nonmagnetic material, the conventional wisdom is that the magnetic interactions between the magnetic ions in the material will be weakened. Neutron Analysis Reveals Unique Atomic-Scale Behavior of "Cobalt Blue" September 01, 2011 - Neutron scattering studies of "cobalt blue," a
Stripe-to-bubble transition of magnetic domains at the spin reorientation of (Fe/Ni)/Cu/Ni/Cu(001)
Magnetic domain evolution at the spin reorientation transition (SRT) of (Fe/Ni)/Cu/Ni/Cu(001) is investigated using photoemission electron microscopy. While the (Fe/Ni) layer exhibits the SRT, the interlayer coupling of the perpendicularly magnetized Ni layer to the (Fe/Ni) layer serves as a virtual perpendicular magnetic field exerted on the (Fe/Ni) layer. We find that the perpendicular virtual magnetic field breaks the up-down symmetry of the (Fe/Ni) stripe domains to induce a net magnetization in the normal direction of the film. Moreover, as the virtual magnetic field increases to exceed a critical field, the stripe domain phase evolves into a bubble domain phase. Although the critical field depends on the Fe film thickness, we show that the area fraction of the minority domain exhibits a universal value that determines the stripe-to-bubble phase transition.
Wu, J.; Choi, J.; Won, C.; Wu, Y. Z.; Scholl, A.; Doran, A.; Hwang, Chanyong; Qiu, Z.
Probing the spin polarization of current by soft x-ray imaging of current-induced magnetic vortex dynamics
Time-resolved soft X-ray transmission microscopy is applied to image the current-induced resonant dynamics of the magnetic vortex core realized in a micron-sized Permalloy disk. The high spatial resolution better than 25 nm enables us to observe the resonant motion of the vortex core. The result also provides the spin polarization of the current to be 0.67 {+-} 0.16 for Permalloy by fitting the experimental results with an analytical model in the framework of the spin-transfer torque.
Kasai, Shinya; Fischer, Peter; Im, Mi-Young; Yamada, Keisuke; Nakatani, Yoshinobu; Kobayashi, Kensuke; Kohno, Hiroshi; Ono, Teruo
Studies of transition metal and overlayers dynamics and magnetism by HE and spin-polarized metastable HE beam spectroscopies
Experimental results for the investigation of quantum delocalization of hydrogen on the Pd(111) surface; the investigation of the structural and dynamical trends in the growth of Cu overlayers on Pd(111) surface; and the investigation of the magnetic structure of the NiO(111) surface using spin-polarized metastable He beam scattering are included in this paper. Planned research is also discussed.
El-Batanouny, M.
Magnet-only loudspeaker motors: linear behavior theory vs. Nonlinear measurements
Magnet-only loudspeaker motors: linear behavior theory vs. Nonlinear measurements A. Novaka and B, the exclusive use of permanent magnets and the absence of iron can lead to uniform motor parameters (force [6] presented loudspeaker distortion reduction us- ing bonded magnet-only motors. Advantages
Paris-Sud XI, Université de
Magnetic and M�ssbauer Behavior of Iron Oxide Nanoparticles ...
Binary and Ternary Phase Diagram Studies of Thermal Energy Storage Materials ... of Core-shell Structured Multiferroic Nanocomposites for Energy Harvesting .... Low-temperature Spin Spray Deposited Ferrite/Piezoelectric Thin Film ... Multi-
Search for magnetic dipole strength and giant spin-flip resonances in heavy nuclei. [120 to 200 MeV
A description is given of the use of high-resolution (n,n) scattering and the (p,n) reaction as tools to investigate highly excited states, with emphasis on information pertaining to magnetic dipole strength and giant spin-flip resonances in heavy nuclei. It is shown how the ability to determine uniquely the spins and parities of resonances observed in neutron scattering has been instrumental to an understanding of the distribution of M1 strength in /sup 207/ /sup 208/Pb. Some recent results of (p,n) studies with intermediate energy protons are discussed. Energy systematics of the giant Gamow-Teller (GT) resonance as well as new ..delta..l = ..delta..S = 1 resonance with J/sup ..pi../ = (1,2)/sup -/ are presented. It is shown how the (p,n) reaction might be useful in locating M1 strength in heavy nuclei. 20 figures.
Horen, D.J.
Optimizing a low-energy electron diffraction spin-polarization analyzer for imaging of magnetic surface structures
A newly designed scanning electron microscope with polarization analysis (SEMPA or spin-SEM) for the acquisition of magnetic images is presented. Core component is the spin detector, based on the scattering of low-energy electrons at a W(100) surface in ultrahigh vacuum. The instrument has been optimized with respect to ease of handling and efficiency. The operation and performance of a general low-energy electron diffraction (LEED) detector for SEMPA have been modeled in order to find the optimum operating parameters and to predict the obtainable image asymmetry. Based on the energy dependence of the secondary electron polarization and intensity, the detector output is simulated. For our instrument with optimized performance we demonstrate experimentally 8.6% polarization asymmetry in the domain structure of an iron whisker. This corresponds to 17.2% image contrast, in excellent agreement with the predicted simulated value. A contrast to noise ratio of 27 is achieved at 5 ms acquisition time per pixel.
Froemter, Robert; Hankemeier, Sebastian; Oepen, Hans Peter [Institut fuer Angewandte Physik, Universitaet Hamburg, Jungiusstr. 11, 20355 Hamburg (Germany); Kirschner, Juergen [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany)
Dynamics of quantum spin liquid and spin solid phases in IPA-CuCl3 under an applied magnetic field studied with neutron scattering
Inelastic and elastic neutron scattering is used to study spin correlations in the quasi-one-dimensional quantum antiferromagnet IPA-CuCl3 in strong applied magnetic fields. A condensation of magnons and commensurate transverse long-range ordering is observe at a critical field Hc=9.5 T. The field dependencies of the energies and polarizations of all magnon branches are investigated both below and above the transition point. Their dispersion is measured across the entire one-dimensional Brillouin zone in magnetic fields up to 14 T. The critical wave vector of magnon spectrum truncation Masuda et al., Phys. Rev. Lett. 96, 047210 2006 is found to shift from hc0,35 at HHC to hc=0.25 for HHC. A drastic reduction of magnon bandwidths in the ordered phase Garlea et al., Phys. Rev. Lett. 98, 167202 2007 is observed and studied in detail. New features of the spectrum, presumably related to this bandwidth collapse, are observed just above the transition field.
Zheludev, Andrey I [ORNL; Garlea, Vasile O [ORNL; Masuda, T. [Yokohama City University, Japan; Manaka, H. [Kagoshima University, Kagoshima JAPAN; Regnault, L.-P. [CEA, Grenoble, France; Ressouche, E. [CEA, Grenoble, France; Grenier, B. [CEA, Grenoble, France; Chung, J.-H. [National Institute of Standards and Technology (NIST); Qiu, Y. [National Institute of Standards and Technology (NIST); Habicht, Klaus [Hahn-Meitner Institut, Berlin, Germany; Kiefer, K. [Hahn-Meitner Institut, Berlin, Germany; Boehm, Martin [Institut Laue-Langevin (ILL)
Level crossings and zero-field splitting in the {Cr8}-cubane spin-cluster studied using inelastic neutron scattering and magnetization
Inelastic neutron scattering (INS) in variable magnetic field and high-field magnetization measurements in the millikelvin temperature range were performed to gain insight into the low-energy magnetic excitation spectrum and the field-induced level crossings in the molecular spin cluster {Cr8}-cubane. These complementary techniques provide consistent estimates of the lowest level-crossing field. The overall features of the experimental data are explained using an isotropic Heisenberg model, based on three distinct exchange interactions linking the eight CrIII paramagnetic centers (spins s = 3/2), that is supplemented with a relatively large molecular magnetic anisotropy term for the lowest S = 1 multiplet. It is noted that the existence of the anisotropy is clearly evident from the magnetic field dependence of the excitations in the INS measurements, while the magnetization measurements are not sensitive to its effects.
Vaknin, D. [Ames Laboratory; Garlea, Vasile O [ORNL; Demmel, F. [ISIS Facility, Rutherford Appleton Laboratory; Mamontov, Eugene [ORNL; Nojiri, H [Institute for Materials Research, Tohoku University, Sendai, Japan; Martin, Catalin [Florida State University; Chiorescu, Irinel [Florida State University; Qiu, Y. [National Institute of Standards and Technology (NIST); Luban, M. [Ames Laboratory; Kogerler, P. [Ames Laboratory; Fielden, J. [Ames Laboratory; Engelhardt, L [Francis Marion University, Florence, South Sarolina; Rainey, C [Francis Marion University, Florence, South Sarolina
Synthesis, structure, and magnetic properties of spin-1/2 kagom� antiferromagnets
Stoichiometrically pure S = 1/2 Cu2+ kagom� materials have been synthesized. Such materials provide an ideal venue for exploration of quantum states on a kagom� because they exhibit strong geometric spin frustration and ...
Nytko, Emily A
Current Controller with Defined Dynamic Behavior for an Interior Permanent Magnet
Current Controller with Defined Dynamic Behavior for an Interior Permanent Magnet Synchronous Motor saturation and changing motor parameters. In this paper a current control scheme is presented that ensures combustion vehicles already provide. Today's modern HEV and EV mostly include interior permanent magnet
Noé, Reinhold
Nuclear Spin Lattice Relaxation and Conductivity Studies of the Non-Arrhenius Conductivity Behavior in Lithium Fast Ion Conducting Sulfide Glasses
As time progresses, the world is using up more of the planet's natural resources. Without technological advances, the day will eventually arrive when these natural resources will no longer be sufficient to supply all of the energy needs. As a result, society is seeing a push for the development of alternative fuel sources such as wind power, solar power, fuel cells, and etc. These pursuits are even occurring in the state of Iowa with increasing social pressure to incorporate larger percentages of ethanol in gasoline. Consumers are increasingly demanding that energy sources be more powerful, more durable, and, ultimately, more cost efficient. Fast Ionic Conducting (FIC) glasses are a material that offers great potential for the development of new batteries and/or fuel cells to help inspire the energy density of battery power supplies. This dissertation probes the mechanisms by which ions conduct in these glasses. A variety of different experimental techniques give a better understanding of the interesting materials science taking place within these systems. This dissertation discusses Nuclear Magnetic Resonance (NMR) techniques performed on FIC glasses over the past few years. These NMR results have been complimented with other measurement techniques, primarily impedance spectroscopy, to develop models that describe the mechanisms by which ionic conduction takes place and the dependence of the ion dynamics on the local structure of the glass. The aim of these measurements was to probe the cause of a non-Arrhenius behavior of the conductivity which has been seen at high temperatures in the silver thio-borosilicate glasses. One aspect that will be addressed is if this behavior is unique to silver containing fast ion conducting glasses. more specifically, this study will determine if a non-Arrhenius correlation time, {tau}, can be observed in the Nuclear Spin Lattice Relaxation (NSLR) measurements. If so, then can this behavior be modeled with a new single distribution of activation energies (DAE) to calculate the corresponding conductivity and relaxation rates as a function of temperature and frequency?
Benjamin Michael Meyer
Intervalley Scattering and Localization Behaviors of Spin-Valley Coupled Dirac Fermions
We study the quantum diffusive transport of multivalley massive Dirac cones, where time-reversal symmetry requires opposite spin orientations in inequivalent valleys. We show that the intervalley scattering and intravalley scattering can be distinguished from the quantum conductivity that corrects the semiclassical Drude conductivity, due to their distinct symmetries and localization trends. In immediate practice, it allows transport measurements to estimate the intervalley scattering rate in holedoped monolayers of group-VI transition metal dichalcogenides (e.g., molybdenum dichalcogenides and tungsten dichalcogenides), an ideal class of materials for valleytronics applications. The results can be generalized to a large class of multivalley massive Dirac systems with spin-valley coupling and timereversal symmetry.
Lu, Hai-Zhou [University of Hong Kong, The; Yao, Wang [University of Hong Kong, The; Xiao, Di [Carnegie Mellon University; Shen, Shun-Qing [University of Hong Kong, The
Paramagnetic spin-up of a field reversed configuration with rotating magnetic field current drive.
??A transverse Rotating Magnetic Field (RMF) can drive toroidal current and sustain the poloidal flux of a Field Reversed Configuration (FRC) through the application of� (more)
Peter, Andrew Maxwell
Energy levels and decoherence properties of single electron and nuclear spins in a defect center in diamond
The coherent behavior of the single electron and single nuclear spins of a defect center in diamond and a 13C nucleus in its vicinity, respectively, are investigated. The energy levels associated with the hyperfine coupling of the electron spin of the defect center to the 13C nuclear spin are analyzed. Methods of magnetic resonance together with optical readout of single defect centers have been applied in order to observe the coherent dynamics of the electron and nuclear spins. Long coherence times, in the order of microseconds for electron spins and tens of microseconds for nuclear spins, recommend the studied system as a good experimental approach for implementing a 2-qubit gate.
I. Popa; T. Gaebel; M. Domhan; C. Wittmann; F. Jelezko; J. Wrachtrup
Determination of the Fe magnetic anisotropies and the CoO frozen spins in epitaxial CoO/Fe/Ag(001)
CoO/Fe/Ag(001) films were grown epitaxially and studied by X-ray Magnetic Circular Dichroism (XMCD) and X-ray Magnetic Linear Dichroism (XMLD). After field cooling along the Fe[100] axis to 80 K, exchange bias, uniaxial anisotropy, and 4-fold anisotropy of the films were determined by hysteresis loop and XMCD measurements by rotating the Fe magnetization within the film plane. The CoO frozen spins were determined by XMLD measurement as a function of CoO thickness.We find that among the exchange bias, uniaxial anisotropy, and 4-fold anisotropy, only the uniaxial magnetic anisotropy follows thickness dependence of the CoO frozen spins.
Meng, J. Li, Y.; Park, J. S.; Jenkins, C. A.; Arenholz, E.; Scholl, A.; Tan, A.; Son, H.; Zhao, H. W.; Hwang, Chanyong; Qiu, Z. Q.
Scaling Behavior of the First Arrival Time of a Random-Walking Magnetic Domain
We report a universal scaling behavior of the first arrival time of a traveling magnetic domain wall into a finite space-time observation window of a magneto-optical microscope enabling direct visualization of a Barkhausen avalanche in real time. The first arrival time of the traveling magnetic domain wall exhibits a nontrivial fluctuation and its statistical distribution is described by universal power-law scaling with scaling exponents of 1.34 {+-} 0.07 for CoCr and CoCrPt films, despite their quite different domain evolution patterns. Numerical simulation of the first arrival time with an assumption that the magnetic domain wall traveled as a random walker well matches our experimentally observed scaling behavior, providing an experimental support for the random-walking model of traveling magnetic domain walls.
Im, M.-Y.; Lee, S.-H.; Kim, D.-H.; Fischer, P.; Shin, S.-C.
RHIC | Spin Physics
Spin Physics Spin Physics RHIC is the world's only machine capable of colliding high-energy beams of polarized protons, and is a unique tool for exploring the puzzle of the proton's 'missing' spin. In addition to colliding heavy ions, RHIC is able to collide single protons. While these collisions don't produce quark-gluon plasma, they're interesting to physicists for other reasons. Scientists want to know more about a property of particles called 'spin'. Spin is the direction a particle is spinning around an axis as it travels -- just like the Earth spins on its axis as it travels around the sun. Each proton has a specific spin, which helps give it a characteristic magnetic property. spin In this picture of a proton-proton collision, the spin of the particles is shown as arrows circling the spherical particles. The red and green
ARPES Provides Direct Evidence of Spin-Wave Coupling
ARPES Provides Direct Evidence of Spin-Wave Coupling Print ARPES Provides Direct Evidence of Spin-Wave Coupling Print The electronic properties of a metal are determined by the dynamical behavior of its conduction electrons. Conventional band theory accounts for the interaction of the electrons with the static ion lattice. However, coupling to further microscopic degrees of freedom can alter the electron dynamics considerably. For example, "conventional" superconductivity emerges as a result of the electrons' interaction with lattice vibrations (phonons). In magnetic materials, coupling with spin waves (magnons) is also expected. Such interactions may contribute to high-temperature superconductivity in novel materials. Unfortunately, lattice vibrations and spin waves have similar energy scales, hindering detailed study. Researchers have taken a new approach in analyzing the electron bands of ferromagnetic iron. Angle-resolved photoemission spectroscopy (ARPES) provides direct spectroscopic evidence of altered electron mass and energy (quasiparticle formation) in a magnetic solid due to coupling with spin waves.
Sensing remote nuclear spins
Sensing single nuclear spins is a central challenge in magnetic resonance based imaging techniques. Although different methods and especially diamond defect based sensing and imaging techniques in principle have shown sufficient sensitivity, signals from single nuclear spins are usually too weak to be distinguished from background noise. Here, we present the detection and identification of remote single C-13 nuclear spins embedded in nuclear spin baths surrounding a single electron spins of a nitrogen-vacancy centre in diamond. With dynamical decoupling control of the centre electron spin, the weak magnetic field ~10 nT from a single nuclear spin located ~3 nm from the centre with hyperfine coupling as weak as ~500 Hz is amplified and detected. The quantum nature of the coupling is confirmed and precise position and the vector components of the nuclear field are determined. Given the distance over which nuclear magnetic fields can be detected the technique marks a firm step towards imaging, detecting and cont...
Zhao, Nan; Schmid, Berhard; Isoya, Junichi; Markham, Mathew; Twitchen, Daniel; Jelezko, Fedor; Liu, Ren-Bao; Fedder, Helmut; Wrachtrup, J�rg
Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic
Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic Vortices Print Influence of Domain Wall Pinning on the Dynamic Behavior of Magnetic Vortices Print Soft magnetic, micron-sized thin-film structures with magnetic vortices are intriguing systems that may one day be used in ultrafast computer memories. In such systems, the otherwise in-plane magnetization turns perpendicular to the plane at the center of the vortex, forming the vortex core. Because such a core has two possible polarizations (up or down) and can be switched between these two states by a small alternating magnetic field, it could serve as a memory bit in future magnetic memory devices. However, these magnetic structures often contain numerous imperfections such as domain wall pinning sites, which have to be taken into account for the practical application of such systems. To study how these defects affect the dynamics of magnetic vortices, researchers from Belgium, Germany, and the United States investigated square-shaped and disk-shaped thin-film structures with artificially introduced imperfections in the form of nanometer-sized holes. They used time-resolved scanning transmission x-ray microscopy (STXM) at ALS Beamline 11.0.2 to determine the frequency at which these vortices vibrate (their eigenfrequency). The imperfections were found to cause a higher vibrational frequency in square-shaped structures, but did not influence the disk-shaped structures. Knowledge of the frequency is crucial for vortex-based memories, since the electric signal for writing data needs to be precisely tuned to it.
Magnetic behavior of 360� domain walls in patterned magnetic thin films
360� transverse domain walls (360DWs), which form readily from transverse 180� domain walls (180DWs) of opposite sense, demonstrate qualitatively distinct behaviors from their constituent 180DWs and are therefore of interest ...
Mascaro, Mark Daniel
A New Spin on Photoemission Spectroscopy
The electronic spin degree of freedom is of general fundamental importance to all matter. Understanding its complex roles and behavior in the solid state, particularly in highly correlated and magnetic materials, has grown increasingly desirable as technology demands advanced devices and materials based on ever stricter comprehension and control of the electron spin. However, direct and efficient spin dependent probes of electronic structure are currently lacking. Angle Resolved Photoemission Spectroscopy (ARPES) has become one of the most successful experimental tools for elucidating solid state electronic structures, bolstered bycontinual breakthroughs in efficient instrumentation. In contrast, spin-resolved photoemission spectroscopy has lagged behind due to a lack of similar instrumental advances. The power of photoemission spectroscopy and the pertinence of electronic spin in the current research climate combine to make breakthroughs in Spin and Angle Resolved Photoemission Spectroscopy (SARPES) a high priority . This thesis details the development of a unique instrument for efficient SARPES and represents a radical departure from conventional methods. A custom designed spin polarimeter based on low energy exchange scattering is developed, with projected efficiency gains of two orders of magnitude over current state-of-the-art polarimeters. For energy analysis, the popular hemispherical analyzer is eschewed for a custom Time-of-Flight (TOF) analyzer offering an additional order of magnitude gain in efficiency. The combined instrument signifies the breakthrough needed to perform the high resolution SARPES experiments necessary for untangling the complex spin-dependent electronic structures central to today?s condensed matter physics.
Advanced Light Source; Jozwiak, Chris
Cerenkov radiation of spinning particle
The Cerenkov radiation of a neutral particle with magnetic moment is considered, as well as the spin-dependent contribution to the Cerenkov radiation of a charged spinning particle. The corresponding radiation intensity is obtained for an arbitrary value of spin and for an arbitrary spin orientation with respect to velocity.
I. B. Khriplovich
Spin Stability
Stability Stability of Asymmetrically Charged Plasma Dust I. H. Hutchinson Plasma Science and Fusion Center Massachusetts Institute of Technology, Cambridge, MA, USA Recently it has been reported that, under some circumstances, dust particles sus- pended in the sheath edge are observed to spin [1, 2, 3]. The present paper shows that there is a natural electrostatic mechanism that should cause even perfectly spherical par- ticles in a perfectly irrotational, magnetic-field-free flowing plasma to spin. The stability criterion and the final spin state are obtained[4]. When the particle is made of an insulating material, it can support potential dif- ferences around its surface. In the limit of zero conductivity, and ignoring all charging effects other than electron or ion collection, the surface charge density accumulates in such a way as to bring the local electric current density to zero.
Magnetite and magnetite/silver core/shell nanoparticles with diluted magnet-like behavior
In the present work is reported the use of the biopolymer chitosan as template for the preparation of magnetite and magnetite/silver core/shell nanoparticles systems, following a two step procedure of magnetite nanoparticles in situ precipitation and subsequent silver ions reduction. The crystalline and morphological characteristics of both magnetite and magnetite/silver core/shell nanoparticles systems were analyzed by high resolution transmission electron microscopy (HRTEM) and nanobeam diffraction patterns (NBD). The results of these studies corroborate the core/shell morphology and the crystalline structure of the magnetite core and the silver shell. Moreover, magnetization temperature dependent, M(T), measurements show an unusual diluted magnetic behavior attributed to the dilution of the magnetic ordering in the magnetite and magnetite/silver core/shell nanoparticles systems. - Graphical abstract: Biopolymer chitosan was used as stabilization media to synthesize both magnetite and magnetite/silver core/shell nanoparticles. Results of HRTEM and NBD patterns confirm core/shell morphology of the obtained nanoparticles. It was found that the composites show diluted magnet-like behavior.
Garza-Navarro, Marco [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Universidad s/n, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Torres-Castro, Alejandro, E-mail: email@example.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Universidad s/n, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon 66600 (Mexico); Gonzalez, Virgilio; Ortiz, Ubaldo [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Universidad s/n, Cd. Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon 66600 (Mexico); De la Rosa, Elder [Centro de Investigaciones en Optica, A.P. 1-948, Leon Gto. 37160 (Mexico)
Theory of Spin Transfer Torque
... In the phenomenon known as spin transfer torque, a current can give a jolt to thin magnetic layers sandwiched between nonmagnetic materials. ...
Spin-orbit Coupling Induced Magnetism in the d-density Wave Phase of La2-xBaxCuO4 Superconductors
We study the effects of spin-orbit coupling in the d-density wave (DDW) phase. In the low-temperature orthorhombic phase of La{sub 2-x}Ba{sub x}CuO{sub 4}, we find that spin-orbit coupling induces ferromagnetic moments in the DDW phase, which are polarized along the [110] direction with a considerable magnitude. This effect does not exist in the superconducting phase. On the other hand, if the d-density wave order does not exist at zero field, a magnetic field along the [110] direction always induces such a staggered orbital current. We discuss experimental constraints on the DDW states in light of our theoretical predictions.
Wu, Congjun; /Stanford U., Phys. Dept. /Santa Barbara, KITP; Zaanen, Jan; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
Ground State Magnetic Moments of Mirror Nuclei Studied at NSCL
Progress in the measurement of the ground state magnetic moments of mirror nuclei at NSCL is presented. The systematic trend of the spin expectation value $$ and the linear behavior of $\\gamma_p$ versus $\\gamma_n$, both extracted from the magnetic moments of mirror partners, are updated to include all available data.
P. F. Mantica; K. Minamisono
Critical behavior of the aperiodic quantum Ising chain in a transverse magnetic field
The authors consider the quantum spin-1/2 Ising chain in an uniform transverse magnetic field, with an aperiodic sequence of ferromagnetic exchange couplings. This system is a limiting anisotropic case of the classical two-dimensional Ising model with an arbitrary layered modulation. Its formal solution via a Jordan-Winger transformation enables one to obtain a detailed description of the influence of the aperiodic modulation on the singularity of the ground-state energy at the critical point. The key concept is that of the fluctuation of the sums of any number of consecutive couplings at the critical point. When the fluctuation is bounded, the model belongs to the Onsager universality class of the uniform chain. The amplitude of the logarithmic divergence in the specific heat is proportional to the velocity of the fermionic excitations, for which the authors give explicit expressions in most cases of interest, including the periodic and quasiperiodic cases, the Thue-Morse chain, and the random dimer model. When the couplings exhibit an unbounded fluctuation, the critical singularity is shown to be generically similar to that of the critical point, and an exponentially small singular part, for which the authors give a quantitative estimate. In the marginal case of a logarithmically divergent fluctuation, e.g., for the period-doubling sequence or the circle sequence or the circle sequence, there is a negative specific heat exponent [alpha], which varies continuously with the strength of the aperiodic modulation. 55 refs., 2 figs.
Luck, J.M. (Centre D'Etudes de Saclay, Gif-sur-Yvette (France))
Photo of the Week: Controlling Chaos with Magnetic Fields | Department of
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
Controlling Chaos with Magnetic Fields Controlling Chaos with Magnetic Fields Photo of the Week: Controlling Chaos with Magnetic Fields January 18, 2013 - 11:26am Addthis This artistic rendition of "spin vortices" illustrates tiny magnetic vortices that spin according to the polarization of each disk's vortex core. At Argonne National Laboratory, scientists are using alternating magnetic fields to control the behavior of these spin vortices, which are small dots made of iron and nickel. The experiments will help to create new, more efficient magnetic devices -- like the random access memory (RAM) in the device you are using to look at this very photo. Learn more about spin vortices. | Photo courtesy of Sander Munster, Dresden University of Technology.
Spin rotation and birefringence effect for a particle in a high energy storage ring and measurement of the real part of the coherent elastic zero-angle scattering amplitude, electric and magnetic polarizabilities
In the present paper the equations for the spin evolution of a particle in a storage ring are analyzed considering contributions from the tensor electric and magnetic polarizabilities of the particle. Study of spin rotation and birefringence effect for a particle in a high energy storage ring provides for measurement as the real part of the coherent elastic zero-angle scattering amplitude as well as tensor electric and magnetic polarizabilities. We proposed the method for measurement the real part of the elastic coherent zero-angle scattering amplitude of particles and nuclei in a storage ring by the paramagnetic resonance in the periodical in time nuclear pseudoelectric and pseudomagnetic fields.
V. G. Baryshevsky; A. A. Gurinovich
Breakdown by magnetic field in a La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/MgO/Fe spin valve
A La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/MgO/Fe spin valve with inverse tunneling magnetoresistance (TMR) was fabricated on a (100) SrTiO{sub 3} substrate by radio frequency magnetron sputtering. Giant TMR ratios up to 540% were obtained. The breakdown of the spin valve was observed at high magnetic field, which was attributed to the joint action of the invalidation of MgO barrier and the shift of Fermi energy in La{sub 0.7}Sr{sub 0.3}MnO{sub 3} at high magnetic field.
Wu Xiaojie; Meng Jian [State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun 130022 (China); Zhang Zhenzhong [State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Dongnanhu Road, Changchun 130033 (China)
Realizing a lattice spin model with polar molecules
With the recent production of polar molecules in the quantum regime, long-range dipolar interactions are expected to facilitate the understanding of strongly interacting many-body quantum systems and to realize lattice spin models for exploring quantum magnetism. In atomic systems, where interactions require wave function overlap, effective spin interactions on a lattice can be realized via superexchange; however, the coupling is weak and limited to nearest-neighbor interactions. In contrast, dipolar interactions exist in the absence of tunneling and extend beyond nearest neighbors. This allows coherent spin dynamics to persist even at high entropy and low lattice filling. Effects of dipolar interactions in ultracold molecular gases have so far been limited to the modification of chemical reactions. We now report the observation of dipolar interactions of polar molecules pinned in a 3D optical lattice. We realize a lattice spin model with spin encoded in rotational states, prepared and probed by microwaves. This spin-exchange interaction arises from the resonant exchange of rotational angular momentum between two molecules. We observe clear oscillations in the evolution of the spin coherence in addition to an overall decay. The frequency of these oscillations, the strong dependence of the spin coherence time on the lattice filling, and the effect of a multi-pulse sequence designed to reverse dynamics due to two-body exchange interactions all provide evidence of dipolar interactions. We also demonstrate suppression of loss in weak lattices due to a quantum Zeno mechanism. Measurements of these tunneling-induced losses allow us to independently determine the lattice filling factor. These results comprise an initial exploration of the behavior of many-body spin models with direct, long-range spin interactions and lay the groundwork for future studies of many-body dynamics in spin lattices.
Bo Yan; Steven A. Moses; Bryce Gadway; Jacob P. Covey; Kaden R. A. Hazzard; Ana Maria Rey; Deborah S. Jin; Jun Ye
Spin as state variable for computation: prospects and perspectives
Recent experiments on spin devices like magnetic tunnel junctions (MTJ's), domain wall magnets (DWM) and spin valves have led to the possibility of having very high density on-chip memories and logic. While the possibility of having on-chip spin transfer ... Keywords: low power, spin device, state variable, ultra low voltage
Kaushik Roy
Effects of boron composition on tunneling magnetoresistance ratio and microstructure of CoFeB/MgO/CoFeB pseudo-spin-valve magnetic tunnel junctions
The effect of B concentration on the tunneling magnetoresistance (TMR) of (Co{sub 25}Fe{sub 75}){sub 100-x}B{sub x}/MgO/(Co{sub 25}Fe{sub 75}){sub 100-x}B{sub x} (x = 22 and 33) pseudo-spin-valve (P-SV) magnetic tunnel junctions (MTJs) was investigated. The TMR ratios for optimally annealed MTJs with x = 22 and 33 were 340% and 170%, respectively, at room temperature. High resolution transmission electron microscopy (HRTEM) observation showed a weaker (001) texture in the MgO barrier in the MTJ with x = 33. The bottom electrode was not fully crystallized even with a considerable amount of B in the (Co{sub 25}Fe{sub 75}){sub 67}B{sub 33}, while good epitaxy was observed between (001) textured MgO and (Co{sub 25}Fe{sub 75}){sub 78}B{sub 22} electrodes.
Kodzuka, M. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); Ohkubo, T. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Hono, K. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); National Institute for Materials Science, Tsukuba 305-0047 (Japan); Ikeda, S.; Ohno, H. [Center for Spintronics Integrated Systems, Tohoku University, Sendai 980-8577 (Japan); Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Gan, H. D. [Center for Spintronics Integrated Systems, Tohoku University, Sendai 980-8577 (Japan)
Spin-disorder scattering and band structure of the ferromagnetic chalcogenide spinels
Magnetic semiconductors are characterized by the presence of charge carriers and magnetic moments. The interaction between the charge carriers and the magnetic moments leads to a spin splitting of the energy bands, and to spin-disorder scattering of ...
C. Haas
Entanglement of dipolar coupling spins
Entanglement of dipole-dipole interacting spins 1/2 is usually investigated when the energy of interaction with an external magnetic field (the Zeeman energy) is greater than the energy of dipole interactions by three orders. Under this condition only ... Keywords: Dipolar interaction, Entanglement, Spin system
G. B. Furman; V. M. Meerovich; V. L. Sokolovsky
Torsion-induced spin precession
We investigate the motion of a spinning test particle in a spatially-flat FRW-type space-time in the framework of the Einstein-Cartan theory. The space-time has a torsion arising from a spinning fluid filling the space-time. We show that for spinning particles with nonzero transverse spin components, the torsion induces a precession of particle spin around the direction of the fluid spin. We also show that a charged spinning particle moving in a torsion-less spatially-flat FRW space-time in the presence of a uniform magnetic field undergoes a precession of a different character. PACS: 04.40.Nr, 04.90.+e 1
Morteza Mohseni
Spin Transport in Semiconductor heterostructures
The focus of the research performed under this grant has been the investigation of spin transport in magnetic semiconductor heterostructures. The interest in these systems is motivated both by their intriguing physical properties, as the physical embodiment of a spin-polarized Fermi liquid, as well as by their potential applications as spintronics devices. In our work we have analyzed several different problems that affect the spin dynamics in single and bi-layer spin-polarized two-dimensional (2D) systems. The topics of interests ranged from the fundamental aspects of the electron-electron interactions, to collective spin and charge density excitations and spin transport in the presence of the spin-orbit coupling. The common denominator of these subjects is the impact at the macroscopic scale of the spin-dependent electron-electron interaction, which plays a much more subtle role than in unpolarized electron systems. Our calculations of several measurable parameters, such as the excitation frequencies of magneto-plasma modes, the spin mass, and the spin transresistivity, propose realistic theoretical estimates of the opposite-spin many-body effects, in particular opposite-spin correlations, that can be directly connected with experimental measurements.
Domnita Catalina Marinescu
ARPES Provides Direct Evidence ARPES Provides Direct Evidence of Spin-Wave Coupling ARPES Provides Direct Evidence of Spin-Wave Coupling Print Wednesday, 30 March 2005 00:00 The electronic properties of a metal are determined by the dynamical behavior of its conduction electrons. Conventional band theory accounts for the interaction of the electrons with the static ion lattice. However, coupling to further microscopic degrees of freedom can alter the electron dynamics considerably. For example, "conventional" superconductivity emerges as a result of the electrons' interaction with lattice vibrations (phonons). In magnetic materials, coupling with spin waves (magnons) is also expected. Such interactions may contribute to high-temperature superconductivity in novel materials. Unfortunately, lattice vibrations and spin waves have similar energy scales, hindering detailed study. Researchers have taken a new approach in analyzing the electron bands of ferromagnetic iron. Angle-resolved photoemission spectroscopy (ARPES) provides direct spectroscopic evidence of altered electron mass and energy (quasiparticle formation) in a magnetic solid due to coupling with spin waves.
Potential contour shaping and sheath behavior with wall electrodes and near-wall magnetic fields in Hall thrusters
Graphite electrodes are embedded within the discharge channel of a Hall effect thruster to focus ions for improved performance. Cusp-shaped magnetic fields are added around the electrodes to shield the electrodes from high electron current. Internal plasma potential measurements inside the discharge channel show that the presence of floating graphite does not significantly affect the potential contours at 150 V anode potential. Creation of closed contour pockets are observed with the electrodes biased 10 and 30 V above the anode potential. The electrodes also cause a compression of the acceleration region in the thruster. The cause of the changes in the potential contours is attributed to a shifting of discharge electrode from the anode to the electrodes and an expansion of the near-wall plasma sheath. The presence of the cusp magnetic fields is shown to affect the current collected by the electrodes, a behavior associated with modification of the plasma sheath properties due to magnetization of electrons.
Xu, K. G. [Department of Mechanical and Aerospace Engineering, University of Alabama in Huntsville, Huntsville, Alabama 35899 (United States); Dao, H.; Walker, M. L. R. [Department of Aerospace Engineering, Georgia Institute of Technology, Atlanta, Georgia 30318 (United States)
Inhomogeneous magnetism in the doped kagome lattice of LaCuO2.66
The hole-doped kagome lattice of Cu2+ ions in LaCuO2.66 was investigated by nuclear quadrupole resonance (NQR), electron spin resonance (ESR), electrical resistivity, bulk magnetization and specific heat measurements. For temperatures above 180 K, the spin and charge properties show an activated behavior suggestive of a narrow-gap semiconductor. At lower temperatures, the results indicate an insulating ground state which may or may not be charge ordered. While the frustrated spins in remaining patches of the original kagome lattice might not be directly detected here, the observation of coexisting non-magnetic sites, free spins and frozen moments reveals an intrinsically inhomogeneous magnetism. Numerical simulations of a 1/3-diluted kagome lattice rationalize this magnetic state in terms of a heterogeneous distribution of cluster sizes and morphologies near the site-percolation threshold.
Julien, M.-H. [Laboratoire National des Champs Magn�etiques Intenses; Simonet, V [Institut Neel, CNRS-UJF; Canals, B. [Institut Neel, CNRS-UJF; Garlea, Vasile O [ORNL; Bordet, Pierre [Laboratoire of Cristallographie, Grenoble; Darie, Celine [Laboratoire of Cristallographie, Grenoble
Propagation of nonclassical correlations across a quantum spin chain
We study the transport of quantum correlations across a chain of interacting spin-1/2 particles. As a quantitative figure of merit, we choose a symmetric version of quantum discord and compare it with the transported entanglement, addressing various operating regimes of the spin medium. Discord turns out to be better transported for a wide range of working points and initial conditions of the system. We relate this behavior to the efficiency of propagation of a single excitation across the spin chain. Moreover, we point out the role played by a magnetic field in the dynamics of discord in the effective channel embodied by the chain. Our analysis can be interestingly extended to transport processes in more complex networks and the study of nonclassical correlations under general quantum channels.
Campbell, S. [Centre for Theoretical Atomic, Molecular and Optical Physics, School of Mathematics and Physics, Queen's University, Belfast BT7 1NN, Northern Ireland (United Kingdom); Physics Department, University College Cork, Cork (Ireland); Quantum Systems Unit, Okinawa Institute of Science and Technology, Okinawa (Japan); Apollaro, T. J. G. [Dipartimento di Fisica e Astronomia, Universita di Firenze, Via G. Sansone 1, IT-50019 Sesto Fiorentino (Italy); Di Franco, C. [Physics Department, University College Cork, Cork, Republic of Ireland (Ireland); Banchi, L.; Cuccoli, A. [Dipartimento di Fisica e Astronomia, Universita di Firenze, Via G. Sansone 1, IT-50019 Sesto Fiorentino (Italy); INFN Sezione di Firenze, via G.Sansone 1, IT-50019 Sesto Fiorentino (Italy); Vaia, R. [Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, via Madonna del Piano 10, IT-50019 Sesto Fiorentino (Italy); Plastina, F. [Dipartimento di Fisica, Universita della Calabria, IT-87036 Arcavacata di Rende (Italy); INFN Gruppo collegato di Cosenza, Universita della Calabria, IT-87036, Arcavacata di Rende (Italy); Paternostro, M. [Centre for Theoretical Atomic, Molecular and Optical Physics, School of Mathematics and Physics, Queen's University, Belfast BT7 1NN, Northern Ireland (United Kingdom)
Switched Control of Electron Nuclear Spin Systems
In this article, we study control of electron-nuclear spin dynamics at magnetic field strengths where the Larmor frequency of the nucleus is comparable to the hyperfine coupling strength. The quantization axis for the nuclear spin differs from the static B_0 field direction and depends on the state of the electron spin. The quantization axis can be switched by flipping the state of electron spin, allowing for universal control on nuclear spin states. We show that by performing a sequence of flips (each followed by a suitable delay), we can perform any desired rotation on the nuclear spins, which can also be conditioned on the state of the electron spin. These operations, combined with electron spin rotations can be used to synthesize any unitary transformation on the coupled electron-nuclear spin system. We discuss how these methods can be used for design of experiments for transfer of polarization from the electron to the nuclear spins.
Navin Khaneja
Polaron Behavior in CMR Manganites
Polaron Behavior in CMR Manganites Print Polaron Behavior in CMR Manganites Print Spintronic devices manipulate electron spin to sense magnetic fields, store information, or perform logical operations. Colossal magnetoresistive (CMR) manganites are a class of materials under study for future spintronic applications such as nonvolatile magnetic computer memory (MRAM). Researchers have recently used several soft x-ray spectroscopies at the ALS to study a prototypical CMR manganite as it was heated past its Curie temperature-the point at which the material ceases to be magnetic. They were able to observe the formation of polarons: electrons whose interaction with the lattice creates a deformation (energy well) that traps the electron, as a pocket on a pool table traps a billiard ball. For the first time, this provided a direct look inside polaron formation in a CMR material, indicating that electron localization as polarons is a defining characteristic of all CMR materials.
Photo-Induced Spin State Switching In [Fe(bpp){sub 2}](NCS){sub 2{center_dot}}2H{sub 2}O
We present the results of our investigation into the effect of irradiation of green light on the high spin low spin transition behavior of the mononuclear iron(II) compound [Fe(bpp){sub 2}](NCS){sub 2{center_dot}}2H{sub 2}O explored with the help of magnetic as well as Moessbauer spectroscopic studies. It has been found that the compound exhibits molecular bistability under irradiation of light due to LIESST effect.
Bhattacharjee, Ashis [Department of Physics, Visva-Bharati University, Santiniketan -731235 (India); Institut fuer Anorganische Chemie und Analytische Chemie, Johannes-Gutenberg Universitaet, D-55099 Mainz (Germany); Goodwin, Harry A. [School of Chemistry, University of New South Wales, UNSW 2052, Sydney (Australia); Guetlich, Philipp [Institut fuer Anorganische Chemie und Analytische Chemie, Johannes-Gutenberg Universitaet, D-55099 Mainz (Germany)
Studies of transition metal and overlayers dynamics and magnetism by HE and spin-polarized metastable HE beam spectroscopies. Technical progress report, 1 October, 1990--30 September, 1991
Spin Noise Exchange in Coupled Alkali-Metal Vapors
The physics of spin exchange collisions has fueled a large number of discoveries in fundamental physics, chemistry and biology, and has led to several applications in medical imaging and nuclear magnetic resonance. We here report on the experimental observation and theoretical justification of a novel effect, the transfer of spin noise from one atomic species to another, through the mechanism of spin exchange. Essentially, we extend the foundational studies of spin exchange into the deeper layer of quantum fluctuations. The signature of spin noise exchange is an increase of the total spin noise power at low magnetic fields where the two-species spin noise resonances overlap.
A. T. Dellis; M. Loulakis; I. K. Kominis
Investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al alloy with Ag and Mn additions
The investigation of thermal, mechanical and magnetic behaviors of the Cu-11%Al, Cu-11%Al-3%Ag, Cu-11%Al-10%Mn and Cu-11%Al-10%Mn-3%Ag alloys was made using microhardness measurements, differential scanning calorimetry, X-ray diffractometry, scanning electron microscopy, energy dispersion X-ray spectroscopy and magnetic moment change with applied field measurement. The results indicated that the Mn addition changes the phase stability range, the microhardness values and makes undetectable the eutectoid reaction in annealed Cu-11%Al and Cu-11%Al-3%Ag alloys while the presence of Ag does not modify the phase transformation sequence neither microhardness values of the annealed Cu-11%Al and Cu-11%Al-10%Mn alloys, but it increases the magnetic moment of this latter at about 2.7 times and decreases the rates of eutectoid and peritectoid reactions of the former. - Highlights: Black-Right-Pointing-Pointer The microstructure of Cu-Al alloy is modified in the Ag presence. Black-Right-Pointing-Pointer ({alpha} + {gamma}) phase is stabilized down to room temperature when Ag is added to Cu-Al alloy. Black-Right-Pointing-Pointer Ag-rich phase modifies the magnetic characteristics of Cu-Al-Mn alloy.
Silva, R.A.G., E-mail: email@example.com [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil)] [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil); Paganotti, A.; Gama, S. [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil)] [Departamento de Ciencias Exatas e da Terra-UNIFESP, Diadema-SP (Brazil); Adorno, A.T.; Carvalho, T.M.; Santos, C.M.A. [Instituto de Quimica - UNESP, Araraquara-SP (Brazil)] [Instituto de Quimica - UNESP, Araraquara-SP (Brazil)
Neutrino magnetic moment in a magnetized plasma
The contribution of a magnetized plasma to the neutrino magnetic moment is calculated. It is shown that only part of the additional neutrino energy in magnetized plasma connecting with its spin and magnetic field strength defines the neutrino magnetic moment. It is found that the presence of magnetized plasma does not lead to the considerable increase of the neutrino magnetic moment in contrast to the results presented in literature previously.
N. V. Mikheev; E. N. Narynskaya
Measuring the Magnetic Center Behavior of an ILC Superconducting Quadrupole Prototype
The main linacs of the proposed International Linear Collider (ILC) consist of superconducting cavities operated at 2K. The accelerating cavities are contained in a contiguous series of cryogenic modules that also house the main linac quadrupoles, thus the quadrupoles also need to be superconducting. In an early ILC design, these magnets are about 0.6 m long, have cos (2{theta}) coils, and operate at constant field gradients up to 60 T/m. In order to preserve the small beam emittances in the ILC linacs, the e+ and e- beams need to traverse the quadrupoles near their magnetic centers. A quadrupole shunting technique is used to measure the quadrupole alignment with the beams; this process requires the magnetic centers move by no more than about 5 micrometers when their strength is changed. To determine if such tight stability is achievable in a superconducting quadrupole, we at SLAC measured the magnetic center motions in a prototype ILC quadrupole built at CIEMAT in Spain. A rotating coil technique was used with a better than 0.1 micrometer precision in the relative field center position, and less than a 2 micrometer systematic error over 30 minutes. This paper describes the warm-bore cryomodule that houses the quadrupole in its Helium vessel, the magnetic center measurement system, the measured center data and strength and harmonics magnetic data.
Spencer, Cherrill M.; Adolphsen, Chris; Berndt, Martin; Jensen, David R.; Rogers, Ron; Sheppard, John C.; Lorant, Steve St; Weber, Thomas B.; Weisend, John, II; /SLAC; Brueck, Heinrich; /DESY; Toral, Fernando; /Madrid, CIEMAT
Experimental Test of Complementarity by Nuclear Magnetic Resonance Techniques
We have tested complementarity for the ensemble-averaged spin states of nuclei $^{13}$C in the molecule of $^{13}$CHCl$_{3}$ by the use of the spin states of another nuclei $^{1}$H as the path marker. It turns out that the wave-particle duality holds when one merely measures the probability density of quantum states, and that the wave- and particle-like behavior is simultaneously observed with the help of measuring populations and coherence in a single nuclear magnetic resonance(NMR) experiment. Effects of path-marking schemes and causes of the appearance and disappearance of the wave behavior are analysed.
Xiwen Zhu; Ximing Fang; Xinhua Peng; Mang Feng; Kelin Gao; Fei Du
Spin-flip induction of Fano resonance upon electron tunneling through atomic-scale spin structures
The inclusion of inelastic spin-dependent electron scatterings by the potential profiles of a single magnetic impurity and a spin dimer is shown to induce resonance features due to the Fano effect in the transport characteristics of such atomic-scale spin structures. The spin-flip processes leading to a configuration interaction of the system's states play a fundamental role for the realization of Fano resonance and antiresonance. It has been established that applying an external magnetic field and a gate electric field allows the conductive properties of spin structures to be changed radically through the Fano resonance mechanism.
Val'kov, V. V., E-mail: firstname.lastname@example.com; Aksenov, S. V., E-mail: email@example.com [Russian Academy of Sciences, Siberian Branch, Kirensky Institute of Physics (Russian Federation); Ulanov, E. A. [Siberian State Aerospace University (Russian Federation)
Titan's New Build Attracts Magnetic Systems Research Impossible Until Now
Titan's New Build Attracts Magnetic Systems Research Impossible Until Now Titan's New Build Attracts Magnetic Systems Research Impossible Until Now November 01, 2013 Researchers using Titan are studying the behavior of magnetic systems by simulating nickel atoms as they reach their Curie temperature-the threshold between order (right) and disorder (left) when atoms spin into random magnetic directions of fluctuating magnetic strengths, causing the material to lose its magnetism. As simple as magnets seemed during school science lessons (opposites attract, likes repel), improving the performance of magnetic materials and creating new alloys is so complicated Markus Eisenbach, computational scientist at Oak Ridge National Laboratory, has been waiting for a computer that can perform as many as twenty quadrillion calculations per second to
Excitations from a Bose-Einstein Condensate of Magnons in Coupled Spin Ladders
The weakly coupled quasi-one-dimensional spin ladder compound CH32HHNH3CuCl3 is studied by neutron scattering in magnetic fields exceeding the critical field of Bose-Einstein condensation of magnons. Commensurate long-range order and the associated Goldstone mode are detected and found to be similar to those in reference to spin-dimer materials. However, for the upper two massive magnon branches, the observed behavior is totally different, culminating in a drastic collapse of excitation bandwidth beyond the transition point.
Garlea, Vasile O [ORNL; Zheludev, Andrey I [ORNL; Masuda, T. [Yokohama City University, Japan; Manaka, H. [Kagoshima University, Kagoshima JAPAN; Regnault, L.-P. [CEA, Grenoble, France; Ressouche, E. [CEA, Grenoble, France; Grenier, B. [CEA, Grenoble, France; Chung, J.-H. [National Institute of Standards and Technology (NIST); Qiu, Y. [National Institute of Standards and Technology (NIST); Habicht, Klaus [Hahn-Meitner Institut, Berlin, Germany; Kiefer, K. [Hahn-Meitner Institut, Berlin, Germany; Boehm, Martin [Institut Laue-Langevin (ILL)
Whirlpools on the Nanoscale Could Multiply Magnetic Memory
cells housed on nanoscale metal disks, instead of the two-bit magnetic domains of standard magnetic memories. In magnetic vortices, parallel electron spins point either...
Mechanism and assessment of spin transfer torque (STT) based memory
When a sufficient current density passes through the MTJ, the spin-polarized current will exert a spin transfer torque to switch the magnetization of the free layer. This is the fundamental of the novel write mechanism in ...
Loh, Iong Ying
Spinning angle optical calibration apparatus
An optical calibration apparatus is provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting an accurate reproducing of spinning "magic angles" in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the "magic angle" of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation or graduations on a reticle in the magnifying scope is noted. Thereafter, the spinning "magic angle" of a test material having similar nuclear properties to the standard is attained by returning the sample holder back to the originally noted coordinate position.
Beer, Stephen K. (Morgantown, WV); Pratt, II, Harold R. (Morgantown, WV)
An optical calibration apparatus is provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting and accurate reproducing of spinning magic angles in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the magic angle of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation or graduations on a reticle in the magnifying scope is noted. Thereafter, the spinning magic angle of a test material having similar nuclear properties to the standard is attained by returning the sample holder back to the originally noted coordinate position. 2 figs.
Beer, S.K.; Pratt, H.R. II.
Spin Splitting and Spin Current in Strained Bulk Semiconductors
We present a theory for two recent experiments in bulk strained semiconductors and show that a new, previously overlooked, strain spin-orbit coupling term may play a fundamental role. We propose simple experiments that could clarify the origin of strain-induced spin-orbit coupling terms in inversion asymmetric semiconductors. We predict that a uniform magnetization parallel to the electric field will be induced in the samples studied in for specific directions of the applied electric field. We also propose special geometries to detect spin currents in strained semiconductors.
Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
Theoretical study of a localized quantum spin reversal by the sequential injection of spins in a spin quantum dot
This is a theoretical study of the reversal of a localized quantum spin induced by sequential injection of spins for a spin quantum dot that has a quantum spin. The system consists of ``electrode/quantum well(QW)/dot/QW/electrode" junctions, in which the left QW has an energy level of conduction electrons with only up-spin. We consider a situation in which up-spin electrons are sequentially injected from the left electrode into the dot through the QW and an exchange interaction acts between the electrons and the localized spin. To describe the sequentially injected electrons, we propose a simple method based on approximate solutions from the time-dependent Schr$\\ddot{\\rm o}$dinger equation. Using this method, it is shown that the spin reversal occurs when the right QW has energy levels of conduction electrons with only down-spin. In particular, the expression of the reversal time of a localized spin is derived and the upper and lower limits of the time are clearly expressed. This expression is expected to be useful for a rough estimation of the minimum relaxation time of the localized spin to achieve the reversal. We also obtain analytic expressions for the expectation value of the localized spin and the electrical current as a function of time. In addition, we found that a system with the non-magnetic right QW exhibits spin reversal or non-reversal depending on the exchange interaction.
Satoshi Kokado; Kazumasa Ueda; Kikuo Harigaya; Akimasa Sakuma
Superfluid and magnetic states of an ultracold Bose gas with synthetic three-dimensional spin-orbit coupling in an optical lattice
We study ultracold bosonic atoms with the synthetic three-dimensional spin-orbit (SO) coupling in a cubic optical lattice. In the superfluidity phase, the lowest energy band exhibits one, two or four pairs of degenerate single-particle ground states depending on the SO-coupling strengths, which can give rise to the condensate states with spin-stripes for the weak atomic interactions. In the deep Mott-insulator regime, the effective spin Hamiltonian of the system combines three-dimensional Heisenberg exchange interactions, anisotropy interactions and Dzyaloshinskii-Moriya interactions. Based on Monte Carlo simulations, we numerically demonstrate that the resulting Hamiltonian with an additional Zeeman field has a rich phase diagram with spiral, stripe, vortex crystal, and especially Skyrmion crystal spin-textures in each xy-plane layer. The obtained Skyrmion crystals can be tunable with square and hexagonal symmetries in a columnar manner along the z axis, and moreover are stable against the inter-layer spin-spin interactions in a large parameter region.
Dan-Wei Zhang; Ji-Pei Chen; Chuan-Jia Shan; Z. D. Wang; Shi-Liang Zhu
SPINS Publications
... Lee, T. Katsufuji, M. Masaki, S. Park, JRD Copley, and H. Takagi, http://dx.doi.org/10.1103/PhysRevB.68.014432"Unconventional Spin ...
Cavity cooling of an ensemble spin system
We describe how sideband cooling techniques, prevalent in quantum optics, may be applied to large spin ensembles in magnetic resonance. Using the Tavis-Cummings model in the presence of a Rabi drive, we solve a Markovian master equation describing the joint spin-cavity dynamics to derive cooling rates as a function of ensemble size. Our calculations indicate that a spin ensemble containing roughly $10^{11}$ electron spins may be polarized to a non-thermal equilibrium state in a time many orders of magnitude shorter than the typical thermal relaxation time. The described techniques permit the efficient removal of entropy for spin-based quantum information processors and fast polarization of spin samples. The proposed application of a standard technique in quantum optics to magnetic resonance also serves to reinforce the connection between the two fields, which has only recently begun to be explored in detail due to the development of hybrid designs for manufacturing noise-resilient quantum devices.
Christopher J. Wood; Troy W. Borneman; David G. Cory
Effects of elemental distributions on the behavior of MgO-based magnetic tunnel junctions.
Three-dimensional atom-probe tomography and transmission electron microscopy have been utilized to study the effects of Ta getter presputtering and either a Mg or Ru free-layer cap on the elemental distributions and properties of MgO-based magnetic tunnel junctions after annealing. Annealing the samples resulted in crystallization of the amorphous CoFeB layer and diffusion of the majority of the boron away from the crystallized CoFeB layers. The Ta getter presputter is found to reduce the segregation of boron at the MgO/CoFeB interface after annealing, improving the tunneling magnetoresistance of the tunnel junction. This effect is observed for samples with either a Ru free-layer cap or a Mg free-layer cap and is thought to be a result of a reduced oxygen concentration within the MgO due to the effect of Ta getter presputtering. A Ru free-layer cap provides superior magnetic and magnetotransport properties compared to a Mg free-layer cap. Mg from the Mg free-layer cap is observed to diffuse toward the MgO tunnel barrier upon annealing, degrading both the crystalline quality of the CoFeB and magnetic isolation of the CoFeB free-layer from the CoFeB reference-layer. Lateral variations in the B distribution within the CoFeB free-layer are observed in the samples with a Ru free-layer cap, which are associated with crystalline and amorphous grains. The B-rich, amorphous grains are found to be depleted in Fe, while the B-poor crystalline grains are slightly enriched in Fe.
Schreiber, D. K.; Choi, Y. S.; Liu, Y.; Chiaramonti, A. N.; Seidman, D. N.; Petford-Long, A. K. (Center for Nanoscale Materials); ( MSD); (Northwestern Univ.); (Canon-ANELVA Corp.)
Emergent spin
Quantum mechanics and relativity in the continuum imply the well known spin-statistics connection. However for particles hopping on a lattice, there is no such constraint. If a lattice model yields a relativistic field theory in a continuum limit, this constraint must "emerge" for physical excitations. We discuss a few models where a spin-less fermion hopping on a lattice gives excitations which satisfy the continuum Dirac equation. This includes such well known systems such as graphene and staggered fermions.
Michael Creutz
I I Painless Physics Articles BEAM COOLING August 2, 1996 By Leila Belkora, Office of Public Affairs ACCELERATION August 16, 1996 By Dave Finley, Accelerator Division Head RF August 30, 1996 By Pat Colestock, Accelerator Division FIXED TARGET PHYSICS September 20, 1996 By Peter H. Garbincius, Physics Section FIXED TARGET PHYSICS PART DEUX October 16, 1996 By Peter H. Garbincius, Physics Section and Leila Belkora, Office of Public Affaris CROSS SECTION November 1, 1996 By Doreen Wackeroth, Theoretical Physics Edited by Leila Belkora, Office of Public Affaris MAGNETS PART I November 15, 1996 By Hank Glass, Technical Support Section Edited by Donald Sena, Office of Public Affairs MAGNETS PART II January 10, 1997 By Hank Glass, Technical Support Section Edited by Donald Sena, Office of Public Affairs
... doped copper oxide superconductor,� Nature Physics. ... P. Zavalij and MA Green, �Magnetic crystallographic ... of a dimerized antiferromagnet,� J. Phys. ...
A Question: Quantum Critical Phenomena in XY Spin-Chain Systems With Dzyaloshinskii-Moriya Interactions
Jordan-Wigner transformation and Bogolyubov transformation are the main steps of the diagonalization of Hamiltonian and paly an important role in the statistical mechanics calculations for one-dimensional Heisenberg spin chain model. Many methods can be exploited as a tool to detect quantum phase transition, regions of criticality and scaling behavior in the vicinity of a quantum phase transition, such as geometric phase, fidelity susceptibility, order parameter, and entanglement entropy, which have direct relation with Bogolyubov transformation. We diagonalized the Hamiltonian in XY spin-chain systems with Dzyaloshinskii-Moriya interactions, the results shows that only the energy spectrum but not the coefficients of the Bogolyubov transformation depends on DM interaction. Therefore, the DM interaction may not influence the critical magnetic field of quantum phase transitions and not induce new critical regions in the XY spin model. Moreover, we further prove the ideas by the methods of geometric phases in this model.
Chuan-Jia Shan; Wei-Wen Cheng; Ji-Bing Liu; Tang-Kun Liu; Yan-Xia Huang; Hong Li
Unconventional temperature enhanced magnetism in iron telluride
Discoveries of copper and iron-based high-temperature superconductors (HTSC)1-2 have challenged our views of superconductivity and magnetism. Contrary to the pre-existing view that magnetism, which typically involves localized electrons, and superconductivity, which requires freely-propagating itinerant electrons, are mutually exclusive, antiferromagnetic phases were found in all HTSC parent materials3,4. Moreover, highly energetic magnetic fluctuations, discovered in HTSC by inelastic neutron scattering (INS) 5,6, are now widely believed to be vital for the superconductivity 7-10. In two competing scenarios, they either originate from local atomic spins11, or are a property of cooperative spin-density-wave (SDW) behavior of conduction electrons 12,13. Both assume clear partition into localized electrons, giving rise to local spins, and itinerant ones, occupying well-defined, rigid conduction bands. Here, by performing an INS study of spin dynamics in iron telluride, a parent material of one of the iron-based HTSC families, we have discovered that this very assumption fails, and that conduction and localized electrons are fundamentally entangled. In the temperature range relevant for the superconductivity we observe a remarkable redistribution of magnetism between the two groups of electrons. The effective spin per Fe at T 10 K, in the2 antiferromagnetic phase, corresponds to S 1, consistent with the recent analyses that emphasize importance of Hund s intra-atomic exchange15-16. However, it grows to S 3/2 in the disordered phase, a result that profoundly challenges the picture of rigid bands, broadly accepted for HTSC.
Zalinznyak, I. [Brookhaven National Laboratory (BNL); Xu, Zhijun [ORNL; Tranquada, John M. [Brookhaven National Laboratory (BNL); Gu, G. D. [Brookhaven National Laboratory (BNL); Tsvelik, A. [Brookhaven National Laboratory (BNL); Stone, Matthew B [ORNL
Probing spin flip scattering in ballistic nanosystems
Because spin-flip scattering length is longer than the electron mean-free-path in a metal, past studies of spin-flip scattering are limited to the diffusive regime. Spin accumulation in the nanometer sized spacer layer of a magnetic double barrier tunnel junction allows the study of spin flip scattering near ballistic limit. We extract the spin-flip conductance $G_s$ of the spacer layer from magnetoresistance measurements. A linear temperature dependence of $G_s$ is found. The bias voltage dependence shows a quantum well resonance which explains the sharp reduction of the magnetoresistance. At 4.2K $G_s$ yields the mean-free-path (70nm) and the spin-flip length ($1.0$-$2.6\\mu$m).
Zeng, Z. M. [Institute of Physics, Chinese Academy of Science; Feng, J. F. [Institute of Physics, Chinese Academy of Science; Wang, Y. [Institute of Physics, Chinese Academy of Science; Han, Prof. X. F. [Institute of Physics, Chinese Academy of Science; Zhan, W. S. [Institute of Physics, Chinese Academy of Science; Zhang, Xiaoguang [ORNL; Zhang, Z. [Institute of Physics, Chinese Academy of Science
Two Wien Filter Spin Flipper
A new 4pi spin manipulator composed of two Wien filters oriented orthogonally and separated by two solenoids has been installed at the CEBAF/Jefferson Lab photoinjector. The new spin manipulator is used to precisely set the electron spin direction at an experiment in any direction (in or out of plane of the accelerator) and provides the means to reverse, or flip, the helicity of the electron beam on a daily basis. This reversal is being employed to suppress systematic false asymmetries that can jeopardize challenging parity violation experiments that strive to measure increasingly small physics asymmetries [*,**,***]. The spin manipulator is part of the ultra-high vacuum polarized electron source beam line and has been successfully operated with 100keV and 130keV electron beam at high current (>100 microAmps). A unique feature of the device is that spin-flipping requires only the polarity of one solenoid magnet be changed. Performance characteristics of the Two Wien Filter Spin Flipper will be summarized.
Grames, J M; Benesch, J F; Clark, J; Hansknecht, J; Kazimi, R; Machie, D; Poelker, M; Stutzman, M L; Suleiman, R
Model for Entangled States with Spin-Spin Interaction
A system consisting of two neutral spin 1/2 particles is analyzed for two magnetic field perturbations: 1) an inhomogeneous magnetic field over all space, and 2) external fields over a half space containing only one of the particles. The field is chosen to point from one particle to the other, which results in essentially a one-dimensional problem. A number of interesting features are revealed for the first case: the singlet, which has zero potential energy in the unperturbed case, remains unstable in the perturbing field. The spin zero component of the triplet evolves into a bound state with a double well potential, with the possibility of tunneling. Superposition states can be constructed which oscillate between entangled and unentangled states. For the second case, we show that changes in the magnetic field around one particle affect measurements of the spin of the entangled particle not in the magnetic field nonlocally. By using protective measurements, we show it is possible in principle to establish a nonlocal interaction using the two particles, provided the dipole-dipole potential energy does not vanish and is comparable to the potential energy of the particle in the external field.
Yakir Aharonov; Jeeva Anandan; G. Jordan Maclay; Jun Suzuki
Experimental evidence of the spin dependence of electron reflections in magnetic CoFe{sub 2}O{sub 4}/Au/Fe{sub 3}O{sub 4} trilayers
An original epitaxial system consisting of two ferrimagnetic insulator layers (CoFe{sub 2}O{sub 4} and Fe{sub 3}O{sub 4}) separated by a nonmagnetic metallic layer (Au) has been grown. The transport properties in the current in plane geometry indicate that the conduction of the CoFe{sub 2}O{sub 4}/Au/Fe{sub 3}O{sub 4} trilayer takes place within the thin metallic layer. The giant magnetoresistance (GMR) observed (2.6% at 10 K) is associated to the switching from a parallel to an antiparallel configuration of the magnetization of the two ferrite layers and corresponds to the spin dependence of electron reflection at the interfaces with a large contribution of specular reflections. The increase of the GMR (5% at 10 K) in the symmetrical interface CoFe{sub 2}O{sub 4}/Fe{sub 3}O{sub 4}/Au/Fe{sub 3}O{sub 4} system and the effect of the interface roughness on the GMR confirm the presence of this spin-dependent specular reflection.
Snoeck, E.; Gatel, Ch.; Serra, R.; BenAssayag, G.; Moussy, J.-B.; Bataille, A. M.; Pannetier, M.; Gautier-Soyer, M. [CEMES-CNRS, Boite Postal 4347, 31055 Toulouse (France); DSM/DRECAM/CAPMAG, CEA Saclay, 91191 Gif-sur-Yvette (France)
Muon-spin-relaxation measurements of magnetic penetration depth in organic superconductors (BEDT-TTF) sub 2 - X : X =Cu(NCS) sub 2 and Cu(N(CN) sub 2 )Br
The magnetic-field penetration depth {lambda} in the organic superconductors {kappa}-(BEDT-TTF){sub 2} Cu(NCS){sub 2} and {kappa}-(BEDT-TTF){sub 2} Cu(N(CN){sub 2})Br has been measured over a wide temperature region 20 mK{le}{ital T}{le}15 K via the muon-spin-relaxation technique. Linear variation of {lambda} with {ital T} at low temperatures, found in both systems, is consistent with anisotropic superconducting pairings with line nodes in the energy gap. In the latter compound, we observe flux depinning at {ital T}{similar to}5 K, well below {ital T}{sub {ital c}}=12 K.
Le, L.P.; Luke, G.M.; Sternlieb, B.J.; Wu, W.D.; Uemura, Y.J. (Department of Physics, Columbia University, New York, New York 10027 (United States)); Brewer, J.H.; Riseman, T.M. (Department of Physics, University of British Columbia, Vancouver, British Columbia, V6T 2A3 (Canada)); Stronach, C.E. (Department of Physics, Virginia State University, Petersburg, Virginia 23803 (United States)); Saito, G.; Yamochi, H. (Department of Chemistry, Kyoto University, Kyoto 606 (Japan)); Wang, H.H.; Kini, A.M.; Carlson, K.D.; Williams, J.M. (Chemistry and Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States))
Large remnant polarization and magnetic field induced destruction of cycloidal spin structure in Bi{sub 1-x}La{sub x}FeO{sub 3} (0 {<=} x {<=} 0.2)
We prepared a series of Bi{sub 1-x}La{sub x}FeO{sub 3} (0 {<=} x {<=} 0.2) ceramics with a sol-gel method and find that both the magnetization and dielectric constant show an abrupt anomaly near a critical field H{sub c}, which is attributed to the destruction of the cycloidal antiferromagnetic spin structure. The critical field H{sub c} decreases substantially from {approx}20 T for the x = 0 sample [Y. F. Popov et al., JETP Lett. 57, 69 (1993)] to {approx}2.8 T for the x = 0.17 sample and finally to 0 T for the x = 0.2 sample at room temperature (RT). It is also found that H{sub c} increases with decreasing temperature. The variation of H{sub c} with La substitution and temperature can be ascribed to the change in the magnetic anisotropy and isotropic superexchange interaction, respectively. We have also discussed the magnetodielectric effects in these samples in terms of the Ginzburg-Landau theory and the spin-phonon model. Moreover, increasing the doping level of La to 0.15 greatly improves the RT leakage-current and ferroelectric (FE) properties. A RT square-shaped FE hysteresis loop with remnant polarization (2P{sub r}) as high as {approx}64 {mu}C/cm{sup 2} is obtained for the x = 0.15 sample. These results may be important for potential applications in BiFeO{sub 3}-based magnetoelectric devices.
Yin, L. H.; Yang, J.; Zhao, B. C.; Liu, Y.; Tan, S. G.; Tang, X. W.; Dai, J. M.; Song, W. H. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei 230031, People's Republic of China (China)] [Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei 230031, People's Republic of China (China); Sun, Y. P. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei 230031, People's Republic of China (China) [Key Laboratory of Materials Physics, Institute of Solid State Physics, Hefei 230031, People's Republic of China (China); High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, People's Republic of China (China)
Motional Spin Relaxation in Large Electric Fields
We discuss the precession of spin-polarized Ultra Cold Neutrons (UCN) and $^{3}$He atoms in uniform and static magnetic and electric fields and calculate the spin relaxation effects from motional $v\\times E$ magnetic fields. Particle motion in an electric field creates a motional $v\\times E$ magnetic field, which when combined with collisions, produces variations of the total magnetic field and results in spin relaxation of neutron and $^{3}$He samples. The spin relaxation times $T_{1}$ (longitudinal) and $T_{2}$ (transverse) of spin-polarized UCN and $^{3}$He atoms are important considerations in a new search for the neutron Electric Dipole Moment at the SNS \\emph{nEDM} experiment. We use a Monte Carlo approach to simulate the relaxation of spins due to the motional $v\\times E$ field for UCN and for $^{3}$He atoms at temperatures below $600,\\mathrm{mK}$. We find the relaxation times for the neutron due to the $v\\times E$ effect to be long compared to the neutron lifetime, while the $^{3}$He relaxation times may be important for the \\emph{nEDM} experiment.
Riccardo Schmid; B. Plaster; B. W. Filippone
Radical-pair model of magnetoreception with spin-orbit coupling
The mechanism used by migratory birds to orientate themselves using the geomagnetic field is still a mystery in many species. The radical pair mechanism, in which very weak magnetic fields can influence certain types of spin-dependent chemical reactions, leading to biologically observable signals, has recently imposed itself as one of the most promising candidates for certain species. This is thanks both to its extreme sensitivity and its capacity to reproduce results from behavioral studies. Still, in order to gain a directional sensitivity, an anisotropic mechanism is needed. Recent proposals have explored the possibility that such an anisotropy is due to the electron-nucleus hyperfine interaction. In this work we explore a different possibility, in which the anisotropy is due to spin-orbit coupling between the electron spin and its angular momentum. We will show how a spin-orbit-coupling-based magnetic compass can have performances comparable with the usually-studied nuclear-hyperfine based mechanism. Our results could thus help researchers actively looking for candidate biological molecules which may host magnetoreceptive functions, both to describe magnetoreception in birds as well as to develop artificial chemical compass systems.
Neill Lambert; Simone De Liberato; Clive Emary; Franco Nori
Demand Response Spinning Reserve Demonstration
F) Enhanced ACP Date RAA ACP Demand Response � SpinningReserve Demonstration Demand Response � Spinning Reservesupply spinning reserve. Demand Response � Spinning Reserve
Interaction mechanisms and biological effects of static magnetic fields
Mechanisms through which static magnetic fields interact with living systems are described and illustrated by selected experimental observations. These mechanisms include electrodynamic interactions with moving, ionic charges (blood flow and nerve impulse conduction), magnetomechanical interactions (orientation and translation of molecules structures and magnetic particles), and interactions with electronic spin states in charge transfer reactions (photo-induced electron transfer in photosynthesis). A general summary is also presented of the biological effects of static magnetic fields. There is convincing experimental evidence for magnetoreception mechanisms in several classes of lower organisms, including bacteria and marine organisms. However, in more highly evolved species of animals, there is no evidence that the interactions of static magnetic fields with flux densities up to 2 Tesla (1 Tesla [T] = 10{sup 4} Gauss) produce either behavioral or physiolocical alterations. These results, based on controlled studies with laboratory animals, are consistent with the outcome of recent epidemiological surveys on human populations exposed occupationally to static magnetic fields.
Tenforde, T.S.
Design of the Local Spin Polarization at the Organic-Ferromagnetic Interface
By means of ab initio calculations and spin-polarized scanning tunneling microscopy experiments the creation of a complex energy dependent magnetic structure with a tailored spin-polarized interface is demonstrated. We ...
Lazic, Predrag
Controlling the quantum dynamics of a mesoscopic spin bath in diamond
Understanding and mitigating decoherence is a key challenge for quantum science and technology. The main source of decoherence for solid-state spin systems is the uncontrolled spin bath environment. Here, we demonstrate quantum control of a mesoscopic spin bath in diamond at room temperature that is composed of electron spins of substitutional nitrogen impurities. The resulting spin bath dynamics are probed using a single nitrogen-vacancy (NV) centre electron spin as a magnetic field sensor. We exploit the spin bath control to dynamically suppress dephasing of the NV spin by the spin bath. Furthermore, by combining spin bath control with dynamical decoupling, we directly measure the coherence and temporal correlations of different groups of bath spins. These results uncover a new arena for fundamental studies on decoherence and enable novel avenues for spin-based magnetometry and quantum information processing.
G. de Lange; T. van der Sar; M. S. Blok; Z. H. Wang; V. V. Dobrovitski; R. Hanson
Spin rotation of polarized beams in high energy storage ring
The equations for spin evolution of a particle in a storage ring are obtained considering contributions from the tensor electric and magnetic polarizabilities of the particle along with the contributions from spin rotation and birefringence effect in polarized matter of an internal target. % Study of the spin rotation and birefringence effects for a particle in a high energy storage ring provides for measurement both the spin-dependent real part of the coherent elastic zero-angle scattering amplitude and tensor electric (magnetic) polarizabilities.
V. G. Baryshevsky
Magnetic Nanostructures for post-CMOS Electronics
... Using ferromagnetic resonance spectroscopy, we were able to separate edge behavior from �bulk� behavior in Permalloy magnetic nano-stripes. ...
Demand Response Spinning Reserve
Demand Response Spinning Reserve Title Demand Response Spinning Reserve Publication Type Report Year of Publication 2007 Authors Eto, Joseph H., Janine Nelson-Hoffman, Carlos...
Optically Detected Magnetic Resonance Studies on ?-conjugated semiconductor systems
Optically Detected Magnetic Resonance (ODMR) techniques were used to investigate the dynamics of excitons and charge carriers in ?-conjugated organic semiconductors. Degradation behavior of the negative spin-1/2 electroluminescence-detected magnetic resonance (ELDMR) was observed in Alq3 devices. The increase in the resonance amplitude implies an increasing bipolaron formation during degradation, which might be the result of growth of charge traps in the device. The same behavior of the negative spin-1/2 ELDMR was observed in 2wt% Rubrene doped Tris(8-hydroxyquinolinato)aluminium (Alq3) devices. However, with increasing injection current, a positive spin-1/2 ELDMR, together with positive spin 1 triplet powder patterns at {delta}m{sub S}={+-}1 and {delta}m{sub S}={+-}2, emerges. Due to the similarities in the frequency dependences of single and double modulated ELDMR and the photoluminescence-detected magnetic resonance (PLDMR) results in poly[2-methoxy-5-(2 -ethyl-hexyloxy)-1,4-phenyl ene vinylene] (MEH-PPV) films, the mechanism for this positive spin-1/2 ELDMR was assigned to enhanced triplet-polaron quenching under resonance conditions. The ELDMR in rubrene doped Alq3 devices provides a path to investigate charge distribution in the device under operational conditions. Combining the results of several devices with different carrier blocking properties and the results from transient EL, it was concluded trions not only exist near buffer layer but also exist in the electron transport layer. This TPQ model can also be used to explain the positive spin-1/2 PLDMR in poly(3-hexylthiophene) (P3HT) films at low temperature and in MEH-PPV films at various temperatures up to room temperature. Through quantitative analysis, TE-polaron quenching (TPQ) model is shown having the ability to explain most behaviors of the positive spin-1/2 resonance. Photocurrent detected magnetic resonance (PCDMR) studies on MEH-PPV devices revealed a novel transient resonance signal. The signal may originate from the higher concentration of deep traps near cathode. A quantitative analysis based on this assumption was carried out and found to be consistent with the experimental results.
Chen, Ying
Giant magnetoresistance in organic spin valves
Interfacial diffusion between magnetic electrodes and organic spacer layers is a serious problem in the organic spintronics which complicates attempts to understand the spin-dependent transport mechanism and hurts the achievement of a desirably high magnetoresistance (MR). We deposit nanodots instead of atoms onto the organic layer using buffer layer assist growth. Spin valves using this method exhibit a sharper interface and a giant MR of up to {approx}300%. Analysis of the current-voltage characteristics indicates that the spin-dependent carrier injection correlates with the observed MR.
Sun, Da-Li [ORNL; Yin, Lifeng [ORNL; Sun, Chengjun [ORNL; Guo, Hangwen [ORNL; Gai, Zheng [ORNL; Zhang, Xiaoguang [ORNL; Ward, Thomas Z [ORNL; Cheng, Zhaohua [Chinese Academy of Sciences; Shen, Jian [ORNL
Local quenches in frustrated quantum spin chains: Global versus subsystem equilibration
We study the equilibration behavior following local quenches, using frustrated quantum spin chains as an example of interacting closed quantum systems. Specifically, we examine the statistics of the time series of the Loschmidt echo, the trace distance of the time-evolved local density matrix to its average state, and the local magnetization. Depending on the quench parameters, the equilibration statistics of these quantities show features of good or poor equilibration, indicated by Gaussian, exponential, or bistable distribution functions. These universal functions provide valuable tools to characterize the various time-evolution responses and give insight into the plethora of equilibration phenomena in complex quantum systems.
Diez, Mathias [Department of Physics and Astronomy and Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, California 90089-0484 (United States); Department of Physics, University of Konstanz, D-78457 Konstanz (Germany); Chancellor, Nicholas; Haas, Stephan [Department of Physics and Astronomy and Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, California 90089-0484 (United States); Venuti, Lorenzo Campos [Institute for Scientific Interchange (ISI), Viale S. Severo 65, I-10133 Torino (Italy); Zanardi, Paolo [Department of Physics and Astronomy and Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, California 90089-0484 (United States); Institute for Scientific Interchange (ISI), Viale S. Severo 65, I-10133 Torino (Italy)
Universal quantum computation with ordered spin-chain networks
It is shown that anisotropic spin chains with gapped bulk excitations and magnetically ordered ground states offer a promising platform for quantum computation, which bridges the conventional single-spin-based qubit concept with recently developed topological Majorana-based proposals. We show how to realize the single-qubit Hadamard, phase, and {pi}/8 gates as well as the two-qubit controlled-not (cnot) gate, which together form a fault-tolerant universal set of quantum gates. The gates are implemented by judiciously controlling Ising exchange and magnetic fields along a network of spin chains, with each individual qubit furnished by a spin-chain segment. A subset of single-qubit operations is geometric in nature, relying on control of anisotropy of spin interactions rather than their strength. We contrast topological aspects of the anisotropic spin-chain networks to those of p-wave superconducting wires discussed in the literature.
Tserkovnyak, Yaroslav [Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States); Loss, Daniel [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)
This paper proposes a new design of spin flipper for RHIC to obtain full spin flip with the spin tune staying at half integer. The traditional technique of using an rf dipole or solenoid as spin flipper to achieve full spin flip in the presence of full Siberian snake requires one to change the snake configuration to move the spin tune away from half integer. This is not practical for an operational high energy polarized proton collider like RHIC where beam lifetime is sensitive to small betatron tune change. The design of the new spin flipper as well as numerical simulations are presented.
Magnetohydrodynamic spin waves in degenerate electron-positron-ion plasmas
Low frequency magnetosonic waves are studied in magnetized degenerate electron-positron-ion plasmas with spin effects. Using the fluid equations of magnetoplasma with quantum corrections due to the Bohm potential, temperature degeneracy, and spin magnetization energy, a generalized dispersion relation for oblique magnetosonic waves is derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. For three different values of angle {theta}, the generalized dispersion relation is reduced to three different relations under the low frequency magnetohydrodynamic assumptions. It is found that the effect of quantum corrections in the presence of positron concentration significantly modifies the dispersive properties of these modes. The importance of the work relevant to compact astrophysical bodies is pointed out.
Mushtaq, A. [TPPD, PINSTECH Nilore, 44000 Islamabad (Pakistan); National Center for Physics, Shahdrah Valley Road, 44000 Islamabad (Pakistan); Maroof, R.; Ahmad, Zulfiaqr [Institute of Physics and Electronics, University of Peshawar, 25000 Peshawar (Pakistan); Qamar, A. [National Center for Physics, Shahdrah Valley Road, 44000 Islamabad (Pakistan); Institute of Physics and Electronics, University of Peshawar, 25000 Peshawar (Pakistan)
In previous works, we introduced a nonlinear force-free method that self-consistently calculates the instantaneous budgets of free magnetic energy and relative magnetic helicity in solar active regions (ARs). Calculation is expedient and practical, using only a single vector magnetogram per computation. We apply this method to a time series of 600 high-cadence vector magnetograms of the eruptive NOAA AR 11158 acquired by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory over a five-day observing interval. Besides testing our method extensively, we use it to interpret the dynamical evolution in the AR, including eruptions. We find that the AR builds large budgets of both free magnetic energy and relative magnetic helicity, sufficient to power many more eruptions than the ones it gave within the interval of interest. For each of these major eruptions, we find eruption-related decreases and subsequent free-energy and helicity budgets that are consistent with the observed eruption (flare and coronal mass ejection (CME)) sizes. In addition, we find that (1) evolution in the AR is consistent with the recently proposed (free) energy-(relative) helicity diagram of solar ARs, (2) eruption-related decreases occur before the flare and the projected CME-launch times, suggesting that CME progenitors precede flares, and (3) self terms of free energy and relative helicity most likely originate from respective mutual terms, following a progressive mutual-to-self conversion pattern that most likely stems from magnetic reconnection. This results in the non-ideal formation of increasingly helical pre-eruption structures and instigates further research on the triggering of solar eruptions with magnetic helicity firmly placed in the eruption cadre.
Tziotziou, Kostas; Georgoulis, Manolis K. [Research Center for Astronomy and Applied Mathematics (RCAAM) Academy of Athens, 4 Soranou Efesiou Street, Athens, GR-11527 (Greece); Liu Yang [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305-4085 (United States)
A Large Sample Volume Magic Angle Spinning Nuclear Magnetic Resonance Probe for In-Situ Investigations with Constant Flow of Reactants
A large-sample-volume constant-flow magic angle sample spinning (CF-MAS) NMR probe is reported for in-situ studies of the reaction dynamics, stable intermediates/transition states, and mechanisms of catalytic reactions. In our approach, the reactants are introduced into the catalyst bed using a fixed tube at one end of the MAS rotor while a second fixed tube, linked to a vacuum pump, is attached at the other end of the rotor. The pressure difference between both ends of the catalyst bed inside the sample cell space forces the reactants flowing through the catalyst bed, which improves the diffusion of the reactants and products. This design allows the use of a large sample volume for enhanced sensitivity and thus permitting in-situ 13C CF-MAS studies at natural abundance. As an example of application, we show that reactants, products and reaction transition states associated with the 2-butanol dehydration reaction over a mesoporous silicalite supported heteropoly acid catalyst (HPA/meso-silicalite-1) can all be detected in a single 13C CF-MAS NMR spectrum at natural abundance. Coke products can also be detected at natural 13C abundance and under the stopped flow condition. Furthermore, 1H CF-MAS NMR is used to identify the surface functional groups of HPA/meso-silicalite-1 under the condition of in-situ drying . We also show that the reaction dynamics of 2-butanol dehydration using HPA/meso-silicalite-1 as a catalyst can be explored using 1H CF-MAS NMR.
Hu, Jian Z.; Sears, Jesse A.; Mehta, Hardeep S.; Ford, Joseph J.; Kwak, Ja Hun; Zhu, Kake; Wang, Yong; Liu, Jun; Hoyt, David W.; Peden, Charles HF
DD1, Enhanced Spin Injection and Spin Lifetimes in Graphene
Gate tunable spin transport and spin precession in non-local single layer graphene (SLG) spin valves at room temperature (RT) were was demonstrated in 2007.
Quantum Spin Chains and Ladders: Theoretical Concepts and Recent Developments
Institut f¨ur Theoretische Physik H.-J. Mikeska (ITP Hannover) Quantum spin chains and ladders Tbilisi Hannover) Quantum spin chains and ladders Tbilisi, September 19, 2005 2 / 54 #12;Introduction 1 Tbilisi, September 19, 2005 3 / 54 #12;Introduction milestones in low D magnetism Milestones in Low D
Dragon, Norbert
Spin light mode of massive neutrino radiative decay in matter
Using the exact solutions for the Dirac neutrino wave function in presence of matter we study the spin light mode in the process of neutrino transition from initial heavier to final lighter state. The spin light is emitted due to the neutrino nonzero transitional magnetic moment.
Alexander Grigoriev; Alexey Lokhov; Alexander Studenikin
Spin Rotation of Formalism for Spin Tracking
The problem of which coefficients are adequate to correctly represent the spin rotation in vector spin tracking for polarized proton and deuteron beams in synchrotrons is here re-examined in the light of recent discussions. The main aim of this note is to show where some previous erroneous results originated and how to code spin rotation in a tracking code. Some analysis of a recent experiment is presented that confirm the correctness of the assumptions.
Coherence and control of quantum registers based on electronic spin in a nuclear spin bath
We consider a protocol for the control of few-qubit registers comprising one electronic spin embedded in a nuclear spin bath. We show how to isolate a few proximal nuclear spins from the rest of the environment and use them as building blocks for a potentially scalable quantum information processor. We describe how coherent control techniques based on magnetic resonance methods can be adapted to these electronic-nuclear solid state spin systems, to provide not only efficient, high fidelity manipulation of the registers, but also decoupling from the spin bath. As an example, we analyze feasible performances and practical limitations in a realistic setting associated with nitrogen-vacancy centers in diamond.
P. Cappellaro; L. Jiang; J. S. Hodges; M. D. Lukin
Spin Liquid Ground State of the $S=1/2$ Kagome Heisenberg Model
Condensed matter physicists have long sought a realistic two-dimensional (2D) magnetic system whose ground state is a {\\it spin liquid}---a zero temperature state in which quantum fluctuations have melted away any form of magnetic order. The nearest-neighbor $S=1/2$ Heisenberg model on the kagome lattice has seemed an ideal candidate, but in recent years some approximate numerical approaches to it have yielded instead a valence bond crystal. We have used the density matrix renormalization group to perform very accurate simulations on numerous cylinders with circumferences up to 12 lattice spacings, finding instead of the valence bond crystal a singlet-gapped spin liquid with substantially lower energy that appears to have $Z_2$ topological order. Our results, through a combination of very low energy, short correlation lengths and corresponding small finite size effects, a new rigorous energy bound, and consistent behavior on many cylinders, provide strong evidence that the 2D ground state of this model is a gapped spin liquid.
Simeng Yan; David A. Huse; Steven R. White
Magellan Tackles the Mysterious Proton Spin
Magellan Tackles Magellan Tackles Mysterious Proton Spin Magellan Tackles Mysterious Proton Spin July 28, 2011 | Tags: Accelerator Science, Data Transfer, ESnet, Magellan Linda Vu, firstname.lastname@example.com, +1 510 495 2402 The STAR experiment's detector records the decay of subatomic smash-ups to uncover how the fundamental building blocks of the universe work. What makes a proton spin? That is one of the biggest mysteries in physics. Although researchers do not fully understand the underlying physics of this phenomenon, they do know that it contributes to the stability of the universe, magnetic interactions, and are a vital component of technologies like Magnetic Resonance Imaging (MRI) machines that are used in hospitals around the globe. To solve this mystery, researchers are smashing together polarized proton
Low field magnetic resonance imaging
A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.
Pines, Alexander (Berkeley, CA); Sakellariou, Dimitrios (Billancourt, FR); Meriles, Carlos A. (Fort Lee, NJ); Trabesinger, Andreas H. (London, GB)
NMR Laboratory Session #1: Measurement of SpinLattice Relaxation Time T1 and
NMR Laboratory Session #1: Measurement of SpinLattice Relaxation Time T1 and SpinSpin Relaxation setup the NMR instrument so that the magnetic field is locked and the software is running remember to make sure the lock on light is on. ) 3. Insert a NMR tube with a large volume of glycerol
Braun, Paul
Meson Spectrum in Strong Magnetic Fields
We study the relativistic quark-antiquark system embedded in magnetic field. The Hamiltonian containing confinement, one gluon exchange and spin-spin interaction is derived. We analytically follow the evolution of the lowest meson states as a functions of MF strength. Calculating the one gluon exchange interaction energy and spin-spin contribution we have observed, that these corrections remain finite at large magnetic fields, preventing the vanishing of the total rho-meson mass at some B_crit, as previously thought. We display the rho masses as functions of magnetic field in comparison with recent lattice data.
M. A. Andreichikov; B. O. Kerbikov; V. D. Orlovsky; Yu. A. Simonov
Spin Injection Across a Heterojunction: A Ballistic Picture
Spin injection across heterojunctions plays a decisive role in the new field of spintronics. Within the ballistic transport regime, we state a general expression for the spin-injection rate in a heterojunction made of two ballistic electrodes. Both the spin-orbit interaction and interface scattering effect are taken into account. Our model is consistent with the well-documented results of ferromagnetic-metal junctions. It explains the recent experimental results of a dilute-magnetic-semiconductor/semiconductor junction and predicts solutions to enhance the spin-injection rate across a ferromagnetic-semiconductor junction.
Hu, C.-M.; Matsuyama, T.
Maxwell Equation for the Coupled Spin-Charge Wave Propagation
We show that the dissipationless spin current in the ground state of the Rashba model gives rise to a reactive coupling between the spin and charge propagation, which is formally identical to the coupling between the electric and the magnetic fields in the 2 + 1 dimensional Maxwell equation. This analogy leads to a remarkable prediction that a density packet can spontaneously split into two counter propagation packets, each carrying the opposite spins. In a certain parameter regime, the coupled spin and charge wave propagates like a transverse 'photon'. We propose both optical and purely electronic experiments to detect this effect.
Bernevig, B.Andrei; Yu, Xiaowei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
Magnetodynamics and Spin Electronics
... Spintronics exploits the interaction between electrons' spin angular momentum ... stochastic processes in the form of electron microscope images of ...
Persistence of entanglement in thermal states of spin systems
We study and compare the persistence of bipartite and multipartite entanglement in one and two-dimensional spin XY model in an external transverse magnetic field under the effect of thermal excitations. We compare the threshold temperature at which the entanglement vanishes in both cases. We use the concurrence as a measure of the bipartite entanglement and the geometric measure to evaluate the multipartite entanglement of the system. We have found that for the anisotropic and partially anisotropic systems the nearest neighbor bipartite entanglement vanishes asymptotically at much higher magnetic field compared to both the next to nearest neighbor bipartite entanglement and the multipartite entanglement which asymptotically coincide. Also the same behavior was observed for the threshold temperatures where the nearest neighbor bipartite one is much higher than both of the next to nearest neighbor bipartite and multipartite where the latter two coincide asymptotically and the three of them increase monotonically with the magnetic field strength. Thus as the temperature increases to certain value, the threshold, the multipartite entanglement and the bipartite entanglement of the far parts of the system may vanish while the nearest neighbor bipartite entanglement may sustain up to much higher temperature. For the isotropic system, all types of entanglement and threshold temperatures vanish at the same exact small value of the magnetic field. We emphasis the major role played by both the properties of the ground state of the system and the energy gap as well. Furthermore, we found that the quantum effects in the system can be maintained at high temperatures, where we have observed that the different types of entanglements in the lattice sustain at high temperatures if we apply sufficiently high magnetic fields.
Gehad Sadiek; Sabre Kais
Viewing spin structures with soft x-ray microscopy
The spin of the electron and its associated magnetic moment marks the basic unit for magnetic properties of matter. Magnetism, in particular ferromagnetism and antiferromagnetism is described by a collective order of these spins, where the interaction between individual spins reflects a competition between exchange, anisotropy and dipolar energy terms. As a result the energetically favored ground state of a ferromagnetic system is a rather complex spin configuration, the magnetic domain structure. Magnetism is one of the eldest scientific phenomena, yet it is one of the most powerful and versatile utilized physical effects in modern technologies, such as in magnetic storage and sensor devices. To achieve highest storage density, the relevant length scales, such as the bit size in disk drives is now approaching the nanoscale and as such further developments have to deal with nanoscience phenomena. Advanced characterization tools are required to fully understand the underlying physical principles. Magnetic microscopes using polarized soft X-rays offer a close-up view into magnetism with unique features, these include elemental sensitivity due to X-ray magnetic dichroism effects as contrast mechanism, high spatial resolution provided by state-of-the-art X-ray optics and fast time resolution limited by the inherent time structure of current X-ray sources, which will be overcome with the introduction of ultrafast and high brilliant X-ray sources.
Fischer, Peter
Magnetooptical Kerr effect measurements of ultrafast spin dynamics in cobalt nanodots
We present our magnetooptical Kerr effect (MOKE) studies on picosecond spin dynamics in closely spaced rectangular Co dots with sizes ranging from 2�6 ?m2 down to 100 � 300 nm2 under in-plane, picosecond, ... Keywords: Coherent spin dynamics, Kerr effect, femtosecond optical pulses, magnetic nanodots, magnetooptics, picosecond magnetic transients, spintronics
D. Wang; A. Verevkin; R. Sobolewski; R. Adam; A. van der Hart; R. Franchy
Nanostructures, magnetic semiconductors and spintronics
The aim of this paper is to give a brief overview of recent advances in the area of semiconductor nanomaterials, which represent extremely promising applications for materials with the spin-polarized transport of the charge carriers. It is shown on the ... Keywords: Magnetic properties, Nanostructure, Semiconductor, Spin-polarized transport, Spintronics
Paata Kervalishvili; Alexander Lagutin
Continuous spin reorientation transition in epitaxially grown antiferromagnetic NiO thin films
Fe/NiO/MgO/Ag(001) films were grown epitaxially, and the Fe and NiO spin orientations were determined using x-ray magnetic dichroism. We find that the NiO spins are aligned perpendicularly to the in-plane Fe spins. Analyzing both the in-plane and out-of-plane spin components of the NiO layer, we demonstrate unambiguously that the antiferromagnetic NiO spins undergo a continuous spin reorientation transition from the in-plane to out-of-plane directions with increasing of the MgO thickness.
Li, J.; Arenholz, E.; Meng, Y.; Tan, A.; Park, J.; Jin, E.; Son, H.; Wu, J.; Jenkins, C. A.; Scholl, A.; Hwang, Chanyong; Qiu, Z. Q.
Optical, magnetic, and transport behaviors of Ge{sub 1-x}Mn{sub x}Te ferromagnetic semiconductors grown by molecular-beam epitaxy
The optical, magnetic, and transport behaviors of Ge{sub 1-x}Mn{sub x}Te (x=0.24 and 0.55) grown by solid-source molecular-beam epitaxy are investigated. X-ray diffraction shows that Ge{sub 1-x}Mn{sub x}Te crystallizes in rocksalt structure. The temperature-dependent magnetization (M-T) for x=0.55 sample gives a Curie paramagnetic temperature of {theta}{sub p}{approx}180 K, which is consistent with the temperature-dependent resistivity {rho}(T) measurement. Anomalous Hall effect is clearly observed in the samples and can be attributed to extrinsic skew scattering based on the scaling relationship of {rho}{sub xy}{proportional_to}{rho}{sub xx}{sup 1.06}. The magnetoresistance of Ge{sub 1-x}Mn{sub x}Te is isotropic and displays a clear hysterestic loop at low temperature, which resembles that of giant-magnetoresistance granular system in solids.
Chen, W. Q.; Bi, J. F.; Teo, K. L.; Liew, T.; Chong, T. C. [Information Storage Materials Laboratory, Electrical and Computer Engineering Department, National University of Singapore, 4 Engineering Drive 3, Singapore 117576, Singapore and Data Storage Institute, 5 Engineering Drive 1, Singapore 117608 (Singapore); Lim, S. T.; Sim, C. H. [Graduate School for Integrative Sciences and Engineering, National University of Singapore, 28 Medical Drive, Singapore 117456 (Singapore)
Quantum read-out and fast initialization of nuclear spin qubits with electric currents
Nuclear spin qubits have the longest coherence times in the solid state, but their quantum read-out and initialization is a great challenge. We present a theory for the interaction of an electric current with the nuclear spins of donor impurities in semiconductors. The theory yields a sensitivity criterion for quantum detection of nuclear spin states using electrically detected magnetic resonance, as well as an all electrical method for fast nuclear spin qubit initialization.
Noah Stemeroff; Rogerio de Sousa
Coherence of an optically illuminated single nuclear spin qubit
We investigate the coherence properties of individual nuclear spin quantum bits in diamond [Dutt et al., Science, 316, 1312 (2007)] when a proximal electronic spin associated with a nitrogen-vacancy (NV) center is being interrogated by optical radiation. The resulting nuclear spin dynamics are governed by time-dependent hyperfine interaction associated with rapid electronic transitions, which can be described by a spin-fluctuator model. We show that due to a process analogous to motional averaging in nuclear magnetic resonance, the nuclear spin coherence can be preserved after a large number of optical excitation cycles. Our theoretical analysis is in good agreement with experimental results. It indicates a novel approach that could potentially isolate the nuclear spin system completely from the electronic environment.
Liang Jiang; M. V. Gurudev Dutt; Emre Togan; Lily Childress; Paola Cappellaro; Jacob M. Taylor; Mikhail D. Lukin
Soft x-ray microscopy - a powerful analytical tool to image magnetism down to fundamental length and times scales
The magnetic properties of low dimensional solid state matter is of the utmost interest both scientifically as well as technologically. In addition to the charge of the electron which is the base for current electronics, by taking into account the spin degree of freedom in future spintronics applications open a new avenue. Progress towards a better physical understanding of the mechanism and principles involved as well as potential applications of nanomagnetic devices can only be achieved with advanced analytical tools. Soft X-ray microscopy providing a spatial resolution towards 10nm, a time resolution currently in the sub-ns regime and inherent elemental sensitivity is a very promising technique for that. This article reviews the recent achievements of magnetic soft X-ray microscopy by selected examples of spin torque phenomena, stochastical behavior on the nanoscale and spin dynamics in magnetic nanopatterns. The future potential with regard to addressing fundamental magnetic length and time scales, e.g. imaging fsec spin dynamics at upcoming X-ray sources is pointed out.
Spin waves at surfaces and steps in ferromagnets and antiferromagnets
The study of the properties of elementary magnetic excitations - spin waves or magnons - in the neighborhood of surfaces, discontinuities, defects, and impurities is an active field of solid-state magnetism. These modes are of interest for understanding relaxation phenomena as well as chemical reactions catalyzed by magnetic substrates. In this contribution we would like to report two different results: (1) some spectra of the spin-wave modes associated with clean and stepped surfaces of a ferromagnet - the clean and a stepped (001) surface of a face-centered-cubic solid; and (2) the unusual and yet unresolved difficulties encountered when similar procedures are attempted on antiferromagnetic surfaces and steps.
Falicov, L.M.
NMR system and method having a permanent magnet providing a rotating magnetic field
Disclosed herein are systems and methods for generating a rotating magnetic field. The rotating magnetic field can be used to obtain rotating-field NMR spectra, such as magic angle spinning spectra, without having to physically rotate the sample. This result allows magic angle spinning NMR to be conducted on biological samples such as live animals, including humans.
Schlueter, Ross D [Berkeley, CA; Budinger, Thomas F [Berkeley, CA
Electronic Structure and Magnetism in Diluted Magnetic Semiconductors
Electronic Structure and Electronic Structure and Magnetism in Diluted Magnetic Semiconductors Electronic Structure and Magnetism in Diluted Magnetic Semiconductors Print Wednesday, 29 November 2006 00:00 The possibility of using electrons' spins in addition to their charge in information technology has created much enthusiasm for a new field of electronics popularly known as "spintronics." An intensely studied approach to obtaining spin-polarized carriers for data-storage devices is the use of diluted magnetic semiconductors created by doping ions like Mn, Fe, or Co having a net spin into a semiconducting host such as GaAs, ZnO, or GaN. The interaction among these spins leads to ferromagnetic order at low temperatures, which is necessary to create spin-polarized carriers. A research team working at ALS Beamline 4.0.2 and European Synchrotron Radiation Facility Beamline ID8 made a big leap forward in clarifying the microscopic picture of magnetism and anisotropy in Mn-doped GaAs by resolving localized and hybridized d states using angle-dependent x-ray magnetic circular dichroism (XMCD) measurements.
Electronic Structure and Magnetism in Diluted Magnetic Semiconductors Print Electronic Structure and Magnetism in Diluted Magnetic Semiconductors Print The possibility of using electrons' spins in addition to their charge in information technology has created much enthusiasm for a new field of electronics popularly known as "spintronics." An intensely studied approach to obtaining spin-polarized carriers for data-storage devices is the use of diluted magnetic semiconductors created by doping ions like Mn, Fe, or Co having a net spin into a semiconducting host such as GaAs, ZnO, or GaN. The interaction among these spins leads to ferromagnetic order at low temperatures, which is necessary to create spin-polarized carriers. A research team working at ALS Beamline 4.0.2 and European Synchrotron Radiation Facility Beamline ID8 made a big leap forward in clarifying the microscopic picture of magnetism and anisotropy in Mn-doped GaAs by resolving localized and hybridized d states using angle-dependent x-ray magnetic circular dichroism (XMCD) measurements.
Spin-Nematic Squeezing in a Quantum Gas
Exotic types of magnetic order and phases resulting from collective behaviour of quantum spins are an important focus of many-body physics. Nematic or quadrupolar ordering of spins is one such example, which breaks O(3) rotational symmetry, has no magnetic moment and is analogous to the well-known ordering of molecules in nematic phases of liquid crystals. Spin nematic phases have been posited for a variety of condensed matter systems including frustrated quantum magnets, and heavy-fermion and iron-based superconductors, although they are challenging to detect directly. Spin-1 atomic Bose-Einstein condensates provide a natural system to investigate spin-nematic quantum phases with a key advantage that the nematic tensor is directly measurable. Here, we measure spin-nematic fluctuations in a spin-1 condensate following a quench through a nematic to ferromagnetic quantum phase transition and observe quadrature squeezing in the variance of the fluctuations up to -8.3 dB (-10.3 dB corrected for detection noise) b...
Hamley, C D; Hoang, T M; Bookjans, E M; Chapman, M S
Mixed-Spin Pairing Condensates in Heavy Nuclei
We show that the Bogoliubov-de Gennes equations for nuclear ground-state wave functions support solutions in which the condensate has a mixture of spin-singlet and spin-triplet pairing. We find that such mixed-spin condensates do not occur when there are equal numbers of neutrons and protons, but only when there is an isospin imbalance. Using a phenomenological Hamiltonian, we predict that such nuclei may occur in the physical region within the proton dripline. We also solve the Bogoliubov-de Gennes equations with variable constraints on the spin-singlet and spin-triplet pairing amplitudes. For nuclei that exhibit this new pairing behavior, the resulting energy surface can be rather soft, suggesting that there may be low-lying excitations associated with the spin mixing.
Gezerlis, Alexandros; Luo, Y. L. [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States); Bertsch, G. F. [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States); Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1560 (United States)
Novel nuclear magnetic resonance techniques for studying biological molecules
parameters by solid-state nuclear magnetic resonance." J.and R. V. Pound. "Nuclear audiofrequency spectroscopy byresonant heating of the nuclear spin system." Phys. Rev. ,
Laws, David D.
Spin coating apparatus
A spin coating apparatus requires less cleanroom air flow than prior spin coating apparatus to minimize cleanroom contamination. A shaped exhaust duct from the spin coater maintains process quality while requiring reduced cleanroom air flow. The exhaust duct can decrease in cross section as it extends from the wafer, minimizing eddy formation. The exhaust duct can conform to entrainment streamlines to minimize eddy formation and reduce interprocess contamination at minimal cleanroom air flow rates.
Torczynski, John R. (Albuquerque, NM)
A nuclear magnetic resonance probe of Fe-Al and Al20V2Eu intermetallics
Al-rich Fe-Al systems (FeAl2, Fe2 Al5 and Fe4Al13) and Al20V2Eu have complicated structures with quasicrystal-like features making these materials potentially of interest for magnetic behavior. However, there is not much work on these materials. To study the variety of magnetic properties, we use NMR, magnetic susceptibility, specific heat and other methods in this work. The microscopic electronic and magnetic properties of the Al-rich Fe-Al system and Al20V2Eu have been studied via 27Al NMR at temperatures between 4 and 500 K. The results of spin lattice relaxation rates reveal a pseudogap in Fe4Al13 and Fe2Al5 around the Fermi-level in the density of states. Besides, a square well gap with a width of 2 meV and center at Fermi energy was detected by specific heat measurements in Fe2Al5. Both Fe4 Al13 and Fe2Al5 are non-magnetic systems with dilute magnetic defects, while FeAl2 is a concentrated local magnetic moment system. In Al20V2Eu, a crossover was observed in NMR, magnetization and transport measurements. Above 40 K, Eu(2+) local magnetic moments dominate; below 40 K, a transition to a Kondo regime is observed, where the Kondo effect leads to the reduction of localized moments due to the formation of a spin-compensated Kondo cloud. With increasing magnetic field, f electrons participate more and more in excitations near the Fermi level and a heavy-Fermion state was observed through specific heat measurements at high magnetic field.
Chi, Ji
Dimensional crossover in a spin liquid to helimagnet quantum phase transition.
Neutron scattering is used to study magnetic field induced ordering in the quasi-1D quantum spin-tube compound Sul-Cu2Cl4 that in zero field has a non-magnetic spin-liquid ground state. The experiments reveal an incommensurate chiral high-field phase stabilized by a geometric frustration of the magnetic interactions. The measured critical exponents \\beta= 0.235 and \
Garlea, Vasile O [ORNL; Zheludev, Andrey I [ORNL; Habicht, Klaus [Hahn-Meitner Institut, Berlin, Germany; Meissner, Michael [Hahn-Meitner Institut, Berlin, Germany; Grenier, B. [CEA, Grenoble, France; Regnault, L.-P. [CEA, Grenoble, France; Ressouche, E. [CEA, Grenoble, France
On the spin-up/spin-down transitions in accreting X-ray binaries
Accreting X-Ray Binaries display a wide range of behaviours. Some of them are observed to spin up steadily, others to alternate between spin-up and spin-down states, sometimes superimposed on a longer trend of either spin up or spin down. Here we interpret this rich phenomenology within a new model of the disk-magnetosphere interaction. Our model, based on the simplest version of a purely material torque, accounts for the fact that, when a neutron star is in the propeller regime, a fraction of the ejected material does not receive enough energy to completely unbind, and hence falls back into the disk. We show that the presence of this feedback mass component causes the occurrence of multiple states available to the system, for a given, constant value of the mass accretion rate dot{M}_* from the companion star. If the angle chi of the magnetic dipole axis with respect to the perpendicular to the disk is larger than a critical value chi_crit, the system eventually settles in a cycle of spin-up/spin-down transitions for a constant value of dot{M}_* and independent of the initial conditions. No external perturbations are required to induce the torque reversals. The transition from spin up to spin down is often accompanied by a large drop in luminosity. The frequency range spanned in each cycle and the timescale for torque reversals depend on dot{M}_*, the magnetic field of the star, the magnetic colatitude chi, and the degree of elasticity regulating the magnetosphere-disk interaction. The critical angle chi_crit ranges from \\~25-30 deg for a completely elastic interaction to ~40-45 deg for a totally anelastic one. For chi ~< chi_crit, cycles are no longer possible and the long-term evolution of the system is a pure spin up. We specifically illustrate our model in the cases of the X-ray binaries GX 1+4 and 4U 1626-67.
Rosalba Perna; Enrico Bozzo; Luigi Stella
Interaction induced staggered spin-orbit order in two-dimensional electron gas
Decoupling spin and charge transports in solids is among the many prerequisites for realizing spin electronics, spin caloritronics, and spin-Hall effect. Beyond the conventional method of generating and manipulating spin current via magnetic knob, recent advances have expanded the possibility to optical and electrical method which are controllable both internally and externally. Yet, due to the inevitable presence of charge excitations and electrical polarizibility in these methods, the separation between spin and charge degrees of freedom of electrons remains a challenge. Here we propose and formulate an interaction induced staggered spin-orbit order as a new emergent phase of matter. We show that when some form of inherent spin-splitting via Rashba-type spin-orbit coupling renders two helical Fermi surfaces to become significantly nested, a Fermi surface instability arises. To lift this degeneracy, a spontaneous symmetry breaking spin-orbit density wave develops, causing a surprisingly large quasiparticle gapping with chiral electronic states, with no active charge excitations. Since the staggered spin-orbit order is associated with a condensation energy, quantified by the gap value, destroying such spin-orbit interaction costs sufficiently large perturbation field or temperature or de-phasing time. BiAg2 surface state is shown to be a representative system for realizing such novel spin-orbit interaction with tunable and large strength, and the spin-splitting is decoupled from charge excitations.
Das, Tanmoy [Los Alamos National Laboratory
Single-shot readout of an electron spin in silicon
The size of silicon transistors used in microelectronic devices is shrinking to the level where quantum effects become important. While this presents a significant challenge for the further scaling of microprocessors, it provides the potential for radical innovations in the form of spin-based quantum computers and spintronic devices. An electron spin in Si can represent a well-isolated quantum bit with long coherence times because of the weak spin-orbit coupling and the possibility to eliminate nuclear spins from the bulk crystal. However, the control of single electrons in Si has proved challenging, and has so far hindered the observation and manipulation of a single spin. Here we report the first demonstration of single-shot, time-resolved readout of an electron spin in Si. This has been performed in a device consisting of implanted phosphorus donors coupled to a metal-oxide-semiconductor single-electron transistor - compatible with current microelectronic technology. We observed a spin lifetime approaching 1 second at magnetic fields below 2 T, and achieved spin readout fidelity better than 90%. High-fidelity single-shot spin readout in Si opens the path to the development of a new generation of quantum computing and spintronic devices, built using the most important material in the semiconductor industry.
Andrea Morello; Jarryd J. Pla; Floris A. Zwanenburg; Kok W. Chan; Hans Huebl; Mikko Mottonen; Christopher D. Nugroho; Changyi Yang; Jessica A. van Donkelaar; Andrew D. C. Alves; David N. Jamieson; Christopher C. Escott; Lloyd C. L. Hollenberg; Robert G. Clark; Andrew S. Dzurak
Non-Abelian hydrodynamics and the flow of spin in spin-orbit coupled substances
Motivated by the heavy ion collision experiments there is much activity in studying the hydrodynamical properties of non-Abelian (quark-gluon) plasmas. A major question is how to deal with color currents. Although not widely appreciated, quite similar issues arise in condensed matter physics in the context of the transport of spins in the presence of spin-orbit coupling. The key insight is that the Pauli Hamiltonian governing the leading relativistic corrections in condensed matter systems can be rewritten in a language of SU(2) covariant derivatives where the role of the non-Abelian gauge fields is taken by the physical electromagnetic fields: the Pauli system can be viewed as Yang-Mills quantum-mechanics in a 'fixed frame', and it can be viewed as an 'analogous system' for non-Abelian transport in the same spirit as Volovik's identification of the He superfluids as analogies for quantum fields in curved space time. We take a similar perspective as Jackiw and coworkers in their recent study of non-Abelian hydrodynamics, twisting the interpretation into the 'fixed frame' context, to find out what this means for spin transport in condensed matter systems. We present an extension of Jackiw's scheme: non-Abelian hydrodynamical currents can be factored in a 'non-coherent' classical part, and a coherent part requiring macroscopic non-Abelian quantum entanglement. Hereby it becomes particularly manifest that non-Abelian fluid flow is a much richer affair than familiar hydrodynamics, and this permits us to classify the various spin transport phenomena in condensed matter physics in an unifying framework. The 'particle based hydrodynamics' of Jackiw et al. is recognized as the high temperature spin transport associated with semiconductor spintronics. In this context the absence of faithful hydrodynamics is well known, but in our formulation it is directly associated with the fact that the covariant conservation of non-Abelian currents turns into a disastrous non-conservation of the incoherent spin currents of the high temperature limit. We analyze the quantum-mechanical single particle currents of relevance to mesoscopic transport with as highlight the Ahronov-Casher effect, where we demonstrate that the intricacies of the non-Abelian transport render this effect to be much more fragile than its abelian analog, the Ahronov-Bohm effect. We subsequently focus on spin flows protected by order parameters. At present there is much interest in multiferroics where non-collinear magnetic order triggers macroscopic electric polarization via the spin-orbit coupling. We identify this to be a peculiarity of coherent non-Abelian hydrodynamics: although there is no net particle transport, the spin entanglement is transported in these magnets and the coherent spin 'super' current in turn translates into electric fields with the bonus that due to the requirement of single valuedness of the magnetic order parameter a true hydrodynamics is restored. Finally, 'fixed-frame' coherent non-Abelian transport comes to its full glory in spin-orbit coupled 'spin superfluids', and we demonstrate a new effect: the trapping of electrical line charge being a fixed frame, non-Abelian analog of the familiar magnetic flux trapping by normal superconductors. The only known physical examples of such spin superfluids are the {sup 3}He A- and B-phase where unfortunately the spin-orbit coupling is so weak that it appears impossible to observe these effects.
Leurs, B.W.A. [Instituut Lorentz for Theoretical Physics, Leiden University, Leiden (Netherlands)], E-mail: firstname.lastname@example.com; Nazario, Z.; Santiago, D.I.; Zaanen, J. [Instituut Lorentz for Theoretical Physics, Leiden University, Leiden (Netherlands)
Quantum Spin Systems
This article is a short introduction to the general topic of quantum spin systems. After a brief sketch of the history of the subject, the standard mathematical framework for formulating problems and results in quantum spin systems is described. Then, three short sections are devoted to Spontaneaous Symmetry Breaking, Phase transitions, and Dynamcis.
Bruno Nachtergaele
Spin coating of electrolytes
Methods for spin coating electrolytic materials onto substrates are disclosed. More particularly, methods for depositing solid coatings of ion-conducting material onto planar substrates and onto electrodes are disclosed. These spin coating methods are employed to fabricate electrochemical sensors for use in measuring, detecting and quantifying gases and liquids.
Stetter, Joseph R. (Naperville, IL); Maclay, G. Jordan (Maywood, IL)
Nuclear Spins in a Nanoscale Device for Quantum Information Processing
Coherent oscillations between any two levels from four nuclear spin states of I=3/2 have been demonstrated in a nanometre-scale NMR semiconductor device, where nuclear spins are all-electrically controlled. Using this device, we discuss quantum logic operations on two fictitious qubits of the I=3/2 system, and propose a quantum state tomography scheme based on the measurement of longitudinal magnetization, $M_z$.
S. K. Ozdemir; A. Miranowicz; T. Ota; G. Yusa; N. Imoto; Y. Hirayama
Observation of Spin Flips with a Single Trapped Proton
Radio-frequency induced spin transitions of one individual proton are observed. The spin quantum jumps are detected via the continuous Stern-Gerlach effect, which is used in an experiment with a single proton stored in a cryogenic Penning trap. This is an important milestone towards a direct high-precision measurement of the magnetic moment of the proton and a new test of the matter-antimatter symmetry in the baryon sector.
Ulmer, S. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Ruprecht Karls-Universitaet Heidelberg, D-69047 Heidelberg (Germany); Rodegheri, C. C. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Blaum, K. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Ruprecht Karls-Universitaet Heidelberg, D-69047 Heidelberg (Germany); Kracke, H.; Mooser, A.; Walz, J. [Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, D-55099 Mainz (Germany); Helmholtz Institut Mainz, D-55099 Mainz (Germany); Quint, W. [Ruprecht Karls-Universitaet Heidelberg, D-69047 Heidelberg (Germany); GSI--Helmholtzzentrum fuer Schwerionenforschung, D-64291 Darmstadt (Germany)
Summary of the 9th international symposium on high energy spin-physics
Summarizing an international conference in high energy spin physics is never an easy task, because of the wide-ranging subjects in physics and technology that are involved. I have chosen to organize the topics of this conference into three broad categories relating to spin; intrinsic spin; composite spin; and spin, the experimental tool. In the first category, I will briefly revisit some historical and recent developments to set a background. In the second category, composite spin, I will discuss the status and developments in several areas, including magnetic moments of baryons, hyperon polarization in high energy high p {perpendicular} production, transverse polarization and asymmetries from transversely polarized targets in high p {perpendicular} scattering, spin structure of the proton, and the Bjorken sum rule. In the third category, I will discuss the steady, and at times rapid, progress in spin technology. In this part I include recent progress in high energy facilities, and comment on the highlights of the Workshops.
Prescott, C.Y.
Nuclear spin qubits in a trapped-ion quantum computer
Physical systems must fulfill a number of conditions to qualify as useful quantum bits (qubits) for quantum information processing, including ease of manipulation, long decoherence times, and high fidelity readout operations. Since these conditions are hard to satisfy with a single system, it may be necessary to combine different degrees of freedom. Here we discuss a possible system, based on electronic and nuclear spin degrees of freedom in trapped ions. The nuclear spin yields long decoherence times, while the electronic spin, in a magnetic field gradient, provides efficient manipulation, and the optical transitions of the ions assure a selective and efficient initialization and readout.
M. Feng; Y. Y. Xu; F. Zhou; D. Suter
Spin-torque diode spectrum of ferromagnetically coupled (FeB/CoFe)/Ru/(CoFe/FeB) synthetic free layer
We investigated systematically the spin torque diode spectrum of a ferromagnetically coupled (FeB/CoFe)/Ru/(CoFe/FeB) synthetic free layer in an MgO-based magnetic tunnel junction. In the spectra, we observed single peaks shifted to higher frequency with increasing the in-plane magnetic fields, as expected from the ferromagnetic resonance of the FeB/CoFe adjacent to the MgO tunnel barrier. On the other hand, under the perpendicular fields, we observed several peaks below 6 GHz and around 10 GHz, which were rather insensitive to the field. These behaviors are different from our simple calculation taking account the interlayer coupling, suggesting that the excitation of magnetizations occurs in a complicated manner for the synthetic free layers.
Bang, Do; Taniguchi, Tomohiro; Kubota, Hitoshi; Yorozu, Takehiko; Imamura, Hiroshi; Yakushiji, Kay; Fukushima, Akio; Yuasa, Shinji; Ando, Koji [National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono 1-1-1, Tsukuba, Ibaraki 305-8568 (Japan)
Atomic clock transitions in silicon-based spin qubits
A major challenge in using spins in the solid state for quantum technologies is protecting them from sources of decoherence. This can be addressed, to varying degrees, by improving material purity or isotopic composition for example, or active error correction methods such as dynamic decoupling, or even combinations of the two. However, a powerful method applied to trapped ions in the context of frequency standards and atomic clocks, is the use of particular spin transitions which are inherently robust to external perturbations. Here we show that such `clock transitions' (CTs) can be observed for electron spins in the solid state, in particular using bismuth donors in silicon. This leads to dramatic enhancements in the electron spin coherence time, exceeding seconds. We find that electron spin qubits based on CTs become less sensitive to the local magnetic environment, including the presence of 29Si nuclear spins as found in natural silicon. We expect the use of such CTs will be of additional importance for donor spins in future devices, mitigating the effects of magnetic or electric field noise arising from nearby interfaces.
Gary Wolfowicz; Alexei M. Tyryshkin; Richard E. George; Helge Riemann; Nikolai V. Abrosimov; Peter Becker; Hans-Joachim Pohl; Mike L. W. Thewalt; Stephen A. Lyon; John J. L. Morton
Imaging of lateral spin valves with soft x-ray microscopy
We investigated Co/Cu lateral spin valves by means of high-resolution transmission soft x-ray microscopy with magnetic contrast that utilizes x-ray magnetic circular dichroism (XMCD). No magnetic XMCD contrast was observed at the Cu L{sub 3} absorption edge, which should directly image the spin accumulation in Cu. Although electrical transport measurements in a non-local geometry clearly detected the spin accumulation in Cu, which remained unchanged during illumination with circular polarized x-rays at the Co and Cu L{sub 3} absorption edges.
Mosendz, O.; Mihajlovic, G.; Pearson, J. E.; Fischer, P.; Im, M.-Y.; Bader, S. D.; Hoffmann, A.
The Quantum Spin Hall Effect: Theory and Experiment
The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the helical edge states give rise to the quantum spin Hall (QSH) effect, in the absence of any external magnetic field. Here we review a recent theory which predicts that the QSH state can be realized in HgTe/CdTe semiconductor quantum wells. By varying the thickness of the quantum well, the band structure changes from a normal to an 'inverted' type at a critical thickness d{sub c}. We present an analytical solution of the helical edge states and explicitly demonstrate their topological stability. We also review the recent experimental observation of the QSH state in HgTe/(Hg,Cd)Te quantum wells. We review both the fabrication of the sample and the experimental setup. For thin quantum wells with well width d{sub QW} < 6.3 nm, the insulating regime shows the conventional behavior of vanishingly small conductance at low temperature. However, for thicker quantum wells (d{sub QW} > 6.3 nm), the nominally insulating regime shows a plateau of residual conductance close to 2e{sup 2}/h. The residual conductance is independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance is destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, d{sub c} = 6.3 nm, is also independently determined from the occurrence of a magnetic field induced insulator to metal transition.
Konig, Markus; Buhmann, Hartmut; Molenkamp, Laurens W.; /Wurzburg U.; Hughes, Taylor L.; /Stanford U., Phys. Dept.; Liu, Chao-Xing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Qi, Xiao-Liang; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
Spinning fluid cosmology
The dynamics of a spinning fluid in a flat cosmological model is investigated. The space-time is itself generated by the spinning fluid which is characterized by an energy-momentum tensor consisting a sum of the usual perfect-fluid energy-momentum tensor and some Belinfante-Rosenfeld tensors. It is shown that the equations of motion admit a solution for which the fluid four-velocity and four-momentum are not co-linear in general. The momentum and spin densities of the fluid are expressed in terms of the scale factor.
Mohseni, Morteza
PJMRprobe for dynamic-angle spinning K. T. Mueller, G. C. Chingas, and A. Pines
with a pulley attached to the probehead and coupled to a stepping motor outside of the magnet. The choice of a superconducting magnet. This allows the refocusing of nuclear spin magnetization that evolves under anisotropic of motor and gear ratio is based on an analysis of the moments of inertia of the motor and load
Pines, Alexander
Local quantum control of Heisenberg spin chains
Motivated by some recent results of quantum control theory, we discuss the feasibility of local operator control in arrays of interacting qubits modeled as isotropic Heisenberg spin chains. Acting on one of the end spins, we aim at finding piecewise-constant control pulses that lead to optimal fidelities for a chosen set of quantum gates. We analyze the robustness of the obtained results for the gate fidelities to random errors in the control fields, finding that with faster switching between piecewise-constant controls the system is less susceptible to these errors. The observed behavior falls into a generic class of physical phenomena that are related to a competition between resonance- and relaxation-type behavior, exemplified by motional narrowing in NMR experiments. Finally, we discuss how the obtained optimal gate fidelities are altered when the corresponding rapidly varying piecewise-constant control fields are smoothened through spectral filtering.
Heule, Rahel; Bruder, C.; Stojanovic, Vladimir M. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Burgarth, Daniel [Institute for Mathematical Sciences, Imperial College London SW7 2PG (United Kingdom); QOLS, The Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom)
Magnetic Edge States in Graphene
Magnetic confinement in graphene has been of recent and growing interest because its potential applications in nanotechnology. In particular, the observation of the so called magnetic edge states in graphene has opened the possibility to deepen into the generation of spin currents and its applications in spintronics. We study the magnetic edge states of quasi-particles arising in graphene monolayers due to an inhomogeneous magnetic field of a magnetic barrier in the formalism of the two-dimensional massless Dirac equation. We also show how the solutions of such states in each of both triangular sublattices of the graphene are related through a supersymmetric transformation in the quantum mechanical sense.
Gabriela Murguia
Low energy spin dynamics in the spin ice, Ho2Sn2O7
The magnetic properties of Ho{sub 2}Sn{sub 2}O{sub 7} have been investigated and compared to other spin ice compounds. Although the lattice has expanded by 3% relative to the better studied Ho{sub 2}Ti{sub 2}O{sub 7} spin ice, no significant changes were observed in the high temperature properties, T {approx}> 20 K. As the temperature is lowered and correlations develop, Ho{sub 2}Sn{sub 2}O{sub 7} enters its quantum phase at a slightly higher temperature than Ho{sub 2}Ti{sub 2}O{sub 7} and is more antiferromagnetic in character. Below 80 K a weak inelastic mode associated with the holmium nuclear spin system has been measured. The hyperfine field at the holmium nucleus was found to be {approx}700 T.
Ehlers, Georg [ORNL; Huq, Ashfia [ORNL; Diallo, Souleymane Omar [Oak Ridge National Laboratory (ORNL); Adriano, Cris [ORNL; Rule, K [Helmholtz-Zentrum Berlin; Cornelius, A. L. [University of Nevada, Las Vegas; Fouquet, Peter [Institut Laue-Langevin (ILL); Pagliuso, P G [Instituto de Fisica Gleb Wataghin, Unicamp, Brazil; Gardner, Jason [Indiana University
Coherent control of two nuclear spins using the anisotropic hyperfine interaction
We demonstrate coherent control of two nuclear spins mediated by the magnetic resonance of a hyperfine-coupled electron spin. This control is used to create a double nuclear coherence in one of the two electron spin manifolds, starting from an initial thermal state, in direct analogy to the creation of an entangled (Bell) state from an initially pure unentangled state. We identify challenges and potential solutions to obtaining experimental gate fidelities useful for quantum information processing in this type of system.
Yingjie Zhang; Colm A. Ryan; Raymond Laflamme; Jonathan Baugh
Reversing the Circulation of Magnetic Vortices
a magnetic vortex are not actually swirling around the core. What they can do is flip in place, and the core-defined as the area where spins point out of the plane-can be...
Development and characterization of the magnetic plasmatron
The purpose of this thesis is to investigate the plausibility of developing a low current plasmatron fuel reformer that utilizes magnetic fields to hydrodynamically induce spin of the arc discharge. The proof of principle, ...
Anziani, Felipe Rene, 1981-
Optimization of a microwave resonator cavity to perform electron spin resonance measurements on quantum dots
This thesis attempts to improve on an ongoing experiment of detecting electron spin resonance (ESR) on AlGaAs/GaAs lateral quantum dots. The experiment is performed in a 2.5 Tesla magnetic field at temperatures around ...
Burger, Anat
Electrical detection of 31P spin quantum states
In recent years, a variety of solid-state qubits has been realized, including quantum dots, superconducting tunnel junctions and point defects. Due to its potential compatibility with existing microelectronics, the proposal by Kane based on phosphorus donors in Si has also been pursued intensively. A key issue of this concept is the readout of the P quantum state. While electrical measurements of magnetic resonance have been performed on single spins, the statistical nature of these experiments based on random telegraph noise measurements has impeded the readout of single spin states. In this letter, we demonstrate the measurement of the spin state of P donor electrons in silicon and the observation of Rabi flops by purely electric means, accomplished by coherent manipulation of spin-dependent charge carrier recombination between the P donor and paramagnetic localized states at the Si/SiO2 interface via pulsed electrically detected magnetic resonance. The electron spin information is shown to be coupled through the hyperfine interaction with the P nucleus, which demonstrates the feasibility of a recombination-based readout of nuclear spins.
A. R. Stegner; C. Boehme; H. Huebl; M. Stutzmann; K. Lips; M. S. Brandt
Slow spin summary
magnetic resonance spectroscopy offers a new tool for obtaining such information in live ... phenomenon known generally as �line broadening ... Work ...
Magnetometry of random AC magnetic fields using a single Nitrogen-Vacancy center
We report on the use of a single NV center to probe fluctuating AC magnetic fields. Using engineered currents to induce random changes in the field amplitude and phase, we show that stochastic fluctuations reduce the NV center sensitivity and, in general, make the NV response field-dependent. We also introduce two modalities to determine the field spectral composition, unknown a priori in a practical application. One strategy capitalizes on the generation of AC-field-induced coherence 'revivals', while the other approach uses the time-tagged fluorescence intensity record from successive NV observations to reconstruct the AC field spectral density. These studies are relevant for magnetic sensing in scenarios where the field of interest has a non-trivial, stochastic behavior, such as sensing unpolarized nuclear spin ensembles at low static magnetic fields.
Abdelghani Laraoui; Jonathan S. Hodges; Carlos A. Meriles
Laraoui, Abdelghani; Meriles, Carlos A
Spinning fluids reactor
A spinning fluids reactor, includes a reactor body (24) having a circular cross-section and a fluid contactor screen (26) within the reactor body (24). The fluid contactor screen (26) having a plurality of apertures and a circular cross-section concentric with the reactor body (24) for a length thus forming an inner volume (28) bound by the fluid contactor screen (26) and an outer volume (30) bound by the reactor body (24) and the fluid contactor screen (26). A primary inlet (20) can be operatively connected to the reactor body (24) and can be configured to produce flow-through first spinning flow of a first fluid within the inner volume (28). A secondary inlet (22) can similarly be operatively connected to the reactor body (24) and can be configured to produce a second flow of a second fluid within the outer volume (30) which is optionally spinning.
Miller, Jan D; Hupka, Jan; Aranowski, Robert
Interaction Flip Identities for non Centered Spin Glasses
We consider spin glass models with non-centered interactions and investigate the effect, on the random free energies, of flipping the interaction in a subregion of the entire volume. A fluctuation bound obtained by martingale methods produces, with the help of integration by parts technique, a family of polynomial identities involving overlaps and magnetizations.
Pierluigi Contucci; Cristian Giardina'; Claudio Giberti
Spin Asymmetries on Nucleon Experiment at Jefferson Lab
The Spin Asymmetries of the Nucleon Experiment (SANE) of Jefferson Lab is a comprehensive measurement of double spin asymmetries of the proton for both parallel and almost perpendicular spin configurations of the proton spin and the electron beam polarization directions. The experiment will provide both spin structure functions, g2 and g1 and spin observable A2 and A1 of the proton over Q2 region from 2.5 to 6.5 GeV2/c2 and Bjorken x region of 0.3 to 0.8. Using the polarized electron beam of Thomas Jefferson National Accelerator Facility and the polarized frozen NH3 target, the data were taken early 2009 in Hall C of Jefferson Lab. Scattered electrons from the inclusive reaction were detected by the Big Electron Telescope Array (BETA), a new non-magnetic detector with a large acceptance of 194 msr. The current analysis effort is focused on the proton spin structure functions g2 and g1. Physics motivations with the experimental methods will be presented with an overvew of the current status of the data analysis.
Seonho Choi
The Spin Asymmetries of the Nucleon Experiment (SANE) of Jefferson Lab is a comprehensive measurement of double spin asymmetries of the proton for both parallel and almost perpendicular spin configurations of the proton spin and the electron beam polarization directions. The experiment will provide both spin structure functions, g{sub 2} and g{sub 1} and spin observable A{sub 2} and A{sub 1} of the proton over Q{sup 2} region from 2.5 to 6.5 GeV{sup 2}/c{sup 2} and Bjorken x region of 0.3 to 0.8. Using the polarized electron beam of Thomas Jefferson National Accelerator Facility and the polarized frozen NH{sub 3} target, the data were taken early 2009 in Hall C of Jefferson Lab. Scattered electrons from the inclusive reaction were detected by the Big Electron Telescope Array (BETA), a new non-magnetic detector with a large acceptance of 194 msr. The current analysis effort is focused on the proton spin structure functions g{sub 2} and g{sub 1}. Physics motivations with the experimental methods will be presented with an overview of the current status of the data analysis.
Choi, Seonho [Department of Physics, Seoul National University, Seoul 151-747 (Korea, Republic of)
Spin states of para-water and ortho-water molecule in gas and liquid phases
Spin degrees of freedom of water molecule in gas and liquid state were investigated in order to provide a reasonable answer about the unsolved problem of a long-term behavior of water spin isomers. The approach used involves an assumption that molecules change their spin state from a pure state to a mixed one when they interact with some sorts of adsorbent surface. Some models and conceptions of the quantum information processing were used.
V. K. Konyukhov
GSE statistics without spin
Energy levels statistics following the Gaussian Symplectic Ensemble (GSE) of Random Matrix Theory have been predicted theoretically and observed numerically in numerous quantum chaotic systems. However in all these systems there has been one unifying feature: the combination of half-integer spin and time-reversal invariance. Here we provide an alternative mechanism for obtaining GSE statistics that is based on geometric symmetries of a quantum system which alleviates the need for spin. As an example, we construct a quantum graph with a particular discrete symmetry given by the quaternion group Q8. GSE statistics is then observed within one of its subspectra.
Christopher H. Joyner; Sebastian M�ller; Martin Sieber
1H-NMR study of the spin dynamics of fine superparamagnetic nanoparticles
We report a broadband 1H-NMR study of the temperature spin dynamics of nearly monodisperse dextran-coated ?-Fe2O3 magnetic nanoparticles. We observed a maximum in T1?1(T) that decreases in amplitude and shifts toward higher temperatures with increasing field. We suggest that this is related to the progressive superparamagnetic spin blocking of the ferrite core. The data can be explained by assuming a single electronic spin-spin correlation time and introducing a field-dependent distribution of anisotropy energy barriers.
Bordonali, L.; Furukawa, Y.; Kraken, M.; Litterst, F.J.; Sangregorio, C.; Casula, M.F.; Lascialfari, A.
Spin-Polarized Hydrogen publications
For more information about my work on spin-polarized atomic hydrogen, consult the following papers: Godfried, HP, Eliel ...
Study of Catcher Bearings for High Temperature Magnetic Bearing Application
The Electron Energy Corporation (EEC) along with National Aeronautics and Space Administration (NASA) in collaboration with Vibration Control and Electro mechanics Lab (VCEL), Texas A & M University, College Station, TX are researching on high temperature permanent magnet based magnetic bearings. The magnetic bearings are made of high temperature resistant permanent magnets (up to 1000 degrees F). A test rig has been developed to test these magnetic bearings. The test rig mainly consists of two radial bearings, one axial thrust bearing and two catcher bearings. The test rig that the catcher bearing is inserted in is the first ultra-high temperature rig with permanent magnet biased magnetic bearings and motor. The magnetic bearings are permanent magnet based which is a novel concept. The Graphalloy bearings represent a new approach for ultra-high temperature backup bearing applications. One of the main objectives of this research is to insure the mechanical and electrical integrity for all components of the test rig. Some assemblies and accessories required for the whole assembly need to be designed. The assembly methods need to be designed. The preliminary tests for coefficient of friction, Young's modulus and thermal expansion characteristics for catcher bearing material need to be done. A dynamic model needs to be designed for studying and simulating the rotor drop of the shaft onto the catcher bearing using a finite element approach in MATLAB. The assembly of the test rig was completed successfully by developing assembly fixtures and assembly methods. The components of the test rig were tested before assembly. Other necessary systems like Sensor holder system, Graphalloy press fit system were designed, fabricated and tested. The catcher bearing material (Graphalloy) was tested for coefficient of friction and Young's modulus at room and high temperatures. The rotor drop was simulated by deriving a dynamic model, to study the effect of system parameters like clearance, coefficient of friction, negative stiffness, initial spin speed on system behavior. Increasing the friction increases the backward whirl and decreases the rotor stoppage time. Increasing the clearance reduces the stoppage time and increases the peak bearing force. Increasing the initial spin speed increases the rotor stoppage time. The maximum stress encountered for as built conditions is more than allowable limits.
Narayanaswamy, Ashwanth
NIST: Methane Symmetry Operations - Nuclear spin stats
... 9.2 Nuclear spin statistics and overall parities. ... Molecule, Rovibrational species, Nuclear spin functions, Overall species, Statistical weight. ...
NIST: Methane Symmetry Operations - Nuclear spin functions
Methane Symmetry Operations. 9. Symmetry Properties of Laboratory-Fixed Nuclear Spin Functions, Nuclear Spin Statistics, and Parities. ...
Investigation of wettability by NMR microscopy and spin-lattice relaxation
The wettability of reservoir rock has an important impact on the efficiency of oil recovery processes and the distribution of oil and water within the reservoir. One of the potentially useful tools for wettability measurements is nuclear magnetic resonance (NMR) and spin-lattice relaxation. More recently using NMR microscopy NIPER has developed the capability of imaging one- and two-phase fluid systems in reservoir rock at resolutions to 25 microns. Effects seen in the images of fluids within the pore space of rocks near the rock grain surfaces hinted at the possibility of using NMR microscopy to map the wettability variations at grain sites within the pore space. Investigations were begun using NMR microscopy and spin-lattice relaxation time measurements on rock/fluid systems and on well-defined fractional wet model systems to study these effects. Relaxation data has been modelled using the stretched exponential relationship recently introduced. Comparisons of the NMR microscopy results of the model system with the rock results indicate that the observed effects probably do not reflect actual wettability variations within the pore space. The results of the relaxation time measurements reveal that even in the simple model studied, the behavior of two phases is somewhat ambiguous and much more complex and requires more study.
Doughty, D.A.; Tomutsa, Liviu
Giant shot noise due to mechanical transportation of spin-polarized electrons.
We show that single-electron 'shuttling' of electrons in a magnetic nanoelectromechanical single-electron transistor device can be an efficient tool for studying electron spin-flip relaxation on quantum dots. The reason is traced to a spin blockade of the mechanically aided shuttle current that occurs in devices with highly polarized and collinearly magnetized leads. This results in giant peaks in the shot-noise spectral function, wherein the peak heights are only limited by the rate of electronic spin flips. Therefore, we show that nanomechanical spectroscopy of the spin-flip rate is possible, allowing spin-flip relaxation times as long as 10 {micro}s to be detected.
Gorelik, L. Y.; Kulinich, S. I.; Shekhter, R. I.; Jonson, M.; Vinokur, V. M.; Materials Science Division; Chalmers Univ. of Technology; Univ.of Goteborg; B.I. Verkin Inst. for Low Temperature Physics and Engineering; Goteborg Univ.; Heriot-Watt Univ.
Instrument Schedule for SPINS
... [1] Andreas Kreyssig. [1] Ames Laboratory. [2] Iowa State University. [3] Helmholtz Zentrum Berlin. Magnet - 10T, dry, dilfrig insert - Mag10T<1.5. ...
Neutron Scattering Study of Quantum Phase Transitions inIntegral Spin Chains.
Quite a few low-dimensional magnets are quantum-disordered 'spin liquids' with a characteristic gap in the magnetic excitation spectrum. Among these are antiferromagnetic chains of integer quantum spins. Their generic feature are long-lived massive (gapped) excitations (magnons) that are subject to Zeeman splitting in external magnetic fields. The gap in one of the magnon branches decreases with field, driving a soft-mode quantum phase transition. The system then enters a qualitatively new high-field phase. The actual properties at high fields, particularly the spin dynamics, critically depend on the system under consideration. Recent neutron scattering studies of organometallic polymer crystals NDMAP (Haldane spin chains with anisotropy) and NTENP (dimerized S = 1 chains) revealed rich and unique physics.
Zheludev, Andrey I [ORNL
RHIC spin flipper commissioning results
The five AC dipole RHIC spin flipper design in the RHIC Blue ring was first tested during the RHIC 2012 polarized proton operation. The advantage of this design is to eliminate the vertical coherent betatron oscillations outside the spin flipper. The closure of each ac dipole vertical bump was measured with orbital response as well as spin. The effect of the rotating field on the spin motion by the spin flipper was also confirmed by measuring the suppressed resonance at Q{sub s} = 1 - Q{sub osc}.
Bai M.; Roser, T.; Dawson, C.; Kewisch, J.; Makdisi, Y.; Oddo, P.; Pai, C.; Pile, P.
Quantum bath-driven decoherence of mixed spin systems
The decoherence of mixed electron-nuclear spin qubits is a topic of great current importance, but understanding is still lacking: while important decoherence mechanisms for spin qubits arise from quantum spin bath environments with slow decay of correlations, the only analytical framework for explaining observed sharp variations of decoherence times with magnetic field is based on the suppression of classical noise. Here we obtain a general expression for decoherence times of the central spin system which exposes significant differences between quantum-bath decoherence and decoherence by classical field noise. We perform measurements of decoherence times of bismuth donors in natural silicon using both electron spin resonance (ESR) and nuclear magnetic resonance (NMR) transitions, and in both cases find excellent agreement with our theory across a wide parameter range. The universality of our expression is also tested by quantitative comparisons with previous measurements of decoherence around `optimal working points' or `clock transitions' where decoherence is strongly suppressed. We further validate our results by comparison to cluster expansion simulations.
S. J. Balian; Gary Wolfowicz; John J. L. Morton; T. S. Monteiro
Temperature dependence of carrier spin polarization determined from current-induced domain wall motion in a Co/Ni nanowire
We have investigated the temperature dependence of the current-induced magnetic domain wall (DW) motion in a perpendicularly magnetized Co/Ni nanowire at various temperatures and with various applied currents. The carrier spin polarization was estimated from the measured domain wall velocity. We found that it decreased more with increasing temperature from 100 K to 530 K than the saturation magnetization did.
Ueda, K.; Koyama, T.; Hiramatsu, R.; Kobayashi, K.; Ono, T. [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Chiba, D. [Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 322-0012 (Japan); Fukami, S. [Green Innovation Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba, Ibaraki 305-8501 (Japan); Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Tanigawa, H.; Suzuki, T. [RENESAS Electronics Corporation, Sagamihara, Kanagawa 252-5298 (Japan); Ohshima, N. [NEC Energy Device Ltd., 1120 Shimokuzawa, Chuo-ku, Sagamihara, Kanagawa 252-5298 (Japan); Ishiwata, N. [Green Innovation Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba, Ibaraki 305-8501 (Japan); Nakatani, Y. [University of Electro-communications, Chofu, Tokyo 182-8585 (Japan)
On the Rapid Spin-down and Low Luminosity Pulsed Emission from AE Aquarii
AE Aqr is an unusual close binary system with a very short white dwarf spin period, a high spin-down rate, a relatively low quiescent luminosity, and clear pulse signals. The exact nature of the large spin-down power has not been well explained mainly due to the fact that the observed luminosities in various energy ranges are much lower than the spin-down power. We consider an unconventional picture of AE Aqr in which an accreting white dwarf, modeled as a magnetic dipole whose axis is misaligned with the spin axis, is rapidly spun-down via gravitational radiation emission and therefore the spin-down power is not directly connected to any observable electromagnetic emission.
Chul-Sung Choi; Insu Yi
Electric Dipole Moment of Magnetic Monopole
The electric dipole moment of magnetic monopoles with spin is studied in the N=2 supersymmetric gauge theory. The dipole moments of the electric charge distributions, as well as the dipole moments due to the magnetic currents, are calculated. The contribution of charge distribution of the fermion to the gyroelectric ratio is expressed by using zeta(3).
Makoto Kobayashi
Spin Properties of Transition-Metallorganic Self-Assembled Molecules
This report summarizes SRI's accomplishments on the project, 'Spin Properties of Transition-Metallorganic Self-Assembled Molecules' funded by the Office of Basic Energy Sciences, US Department of Energy. We have successfully carried out all tasks identified in our proposal and gained significant knowledge and understanding of spin-polarized electronic structure, spin relaxation, and spin-dependent transport in transition-metallorganic molecules and enhohedral fullerenes. These molecules contain integrated spin and charge components and will enable us to achieve sophisticated functions in spintronics and quantum computing at molecular level with simple circuitry and easy fabrication. We have developed microscopic theories that describe the underlying mechanisms of spin-dependent porcesses and constructed quantitative modeling tools that compute several important spin properties. These results represent the basic principles governing the spin-dependent behaviors in nanostructures containing such molecules. Based on these results we have shown that novel device functions, such as electrically controlled g-factor and noninvasive electrical detection of spin dynamics, can be achieved in these nanostructures. Some of our results have been published in peer-reviewed journals and presented at professional conferences. In addition, we have established a close collaboration with experimentalists at Oxford University, UK (Dr. J. Morton and Prof. G. Briggs), Princeton University (Dr. A. Tyryshkin and Prof. S. Lyon), University of Delaware (Prof. E. Nowak), and University of California (Profs. R. Kawakami and J. Shi), who have been studying related systems and supplying us with new experimental data. We have provided our understanding and physical insights to the experimentalists and helped analyze their experimental measurements. The collaboration with experimentalists has also broadened our research scope and helped us focus on the most relevant issues concerning these materials.
Zhi Gang Yu
Whirlpools on the Nanoscale Could Whirlpools on the Nanoscale Could Multiply Magnetic Memory Whirlpools on the Nanoscale Could Multiply Magnetic Memory Print Tuesday, 21 May 2013 00:00 Research at the Advanced Light Source may lead to four-bit magnetic cells housed on nanoscale metal disks, instead of the two-bit magnetic domains of standard magnetic memories. In magnetic vortices, parallel electron spins point either clockwise or counterclockwise, while in their crowded centers the spins point either down or up. "From the scientist's point of view, magnetism is about controlling electron spin," says Peter Fischer of the Materials Sciences Division, who leads the work at beamline 6.1.2. Four orientations could provide multibits in a new kind of memory. The next step is to control the states independently and simultaneously.
1D Solution NMR Procedure (Bruker AVANCE Machines running TopSpin under WINDOWS XP)
1D Solution NMR Procedure (Bruker AVANCE Machines running TopSpin under WINDOWS XP) Jerry Hu, x7914 NMR yourself; Take everything ferromagnetic or vulnerable to magnetic field, such as mechanic watches them somewhere away from magnets; Table of Contents 1D Solution NMR Procedure
Akhmedov, Azer
Spin effect on parametric interactions of waves in magnetoplasmas
The parametric decay instability of upper hybrid wave into low-frequency electromagnetic Shear Alfven wave and Ordinary mode radiation (O-mode) has been investigated in an electron-ion plasma immersed in the uniform external magnetic field. Incorporating quantum effect due to electron spin, the fluid model has been used to investigate the linear and nonlinear response of the plasma species for three-wave coupling in a magnetoplasma. It is shown that the spin of electrons has considerable effect on the parametric decay of upper hybrid wave into Ordinary mode radiation (O-mode) and Shear Alfven wave even in classical regime.
Shahid, M. [Department of Physics, Government College University, Lahore-54000 (Pakistan); Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan); Melrose, D. B. [School of Physics, University of Sydney, New South Wales 2006 (Australia); Jamil, M. [Department of Physics, Government College University, Faisalabad-38000 (Pakistan); Murtaza, G. [Salam Chair in Physics, Government College University, Lahore-54000 (Pakistan)
Teleparallel Spin Connection
A new expression for the spin connection of teleparallel gravity is proposed, given by minus the contorsion tensor plus a zero connection. The corresponding minimal coupling is covariant under local Lorentz transformation, and equivalent to the minimal coupling prescription of general relativity. With this coupling prescription, therefore, teleparallel gravity turns out to be fully equivalent to general relativity, even in the presence of spinor fields.
V. C. de Andrade; L. C. T. Guillen; J. G. Pereira
Effect of electron-nuclear spin interactions on electron-spin qubits localized in self-assembled quantum dots
The effect of electron-nuclear spin interactions on qubit operations is investigated for a qubit represented by the spin of an electron localized in a self-assembled quantum dot. The localized electron wave function is evaluated within the atomistic tight-binding model. The magnetic field generated by the nuclear spins is estimated in the presence of an inhomogeneous environment characterized by a random nuclear spin configuration, by the dot-size distribution, by alloy disorder, and by interface disorder. Due to these inhomogeneities, the magnitude of the nuclear magnetic field varies from one qubit to another by the order of 100 G, 100 G, 10 G, and 0.1 G, respectively. The fluctuation of the magnetic field causes errors in exchange operations due to the inequality of the Zeeman splitting between two qubits. We show that the errors can be made lower than the quantum error threshold if an exchange energy larger than 0.1 meV is used for the operation.
Seungwon Lee; Paul von Allmen; Fabiano Oyafuso; Gerhard Klimeck; K. Birgitta Whaley
Chemistry AN ALGORITHM FOR THE GENERATION OF NUCLEAR SPINSPECIES AND NUCLEAR SPIN STATISTICAL WEIGHTS K.for the Generation of Nuclear Spin and Nuclear Spin
Balasubramanian, K.
Geometric phase of a central spin coupled to an antiferromagnetic environment
Using the spin-wave approximation, we study the geometric phase (GP) of a central spin (signal qubit) coupled to an antiferromagnetic (AF) environment under the application of an external global magnetic field. The external magnetic field affects the GP of the qubit directly and also indirectly through its effect on the AF environment. We find that when the applied magnetic field is increased to the critical magnetic field point, the AF environment undergoes a spin-flop transition, a first-order phase transition, and at the same time the GP of the qubit changes abruptly to zero. This sensitive change of the GP of a signal qubit to the parameter change of a many-body environment near its critical point may serve as another efficient tool or witness to study the many-body phase transition. The influences of the AF environment temperature and crystal anisotropy field on the GP are also investigated.
Xiao-Zhong Yuan; Hsi-Sheng Goan; Ka-Di Zhu
Magnetics News
... Hall Effect in a Quantum Gas Is Step ... Discovered 'Quantum Spin Liquid', the Beauty ... A TECHNOLOGY TRANSFER AND FEDERAL MARKETPLACE ...
In-situ TEM studies of magnetisation reversal processes in magnetic nanostructures.
One of the most widely studied types of magnetic nanostructure is that used in devices based on the giant magnetoresistance (GMR) or tunnel magnetoresistance (TMR) phenomena. In order to understand the behavior of these materials it is important to be able to follow their magnetization reversal mechanism, and one of the techniques enabling micromagnetic studies at the sub-micron scale is transmission electron microscopy. Two techniques can be used: Lorentz transmission electron microscopy and off-axis electron holography, both of which allow the magnetic domain structure of a ferromagnetic material to be investigated dynamically in real-time with a resolution of a few nanometers. These techniques have been used in combination with in situ magnetizing experiments, to carry out qualitative and quantitative studies of magnetization reversal in a range of materials including spin-tunnel junctions, patterned thin film elements and magnetic antidot arrays. Quantitative analysis of the Lorentz TEM data has been carried out using the transport of intensity equation (TIE) approach.
Petford-Long, A. K.; Bromwich, T.; Kohn, A.; Jackson, V.; Kasama, T.; Dunin-Borkowski, R.; Ross, C. A.; Materials Science Division; Univ. Oxford; Univ. Cambridge; Massachusetts Inst. of Tech.
Layering and temperature-dependent magnetization and anisotropy of naturally produced Ni/NiO multilayers
Ni/NiO multilayers were grown by magnetron sputtering at room temperature, with the aid of the natural oxidation procedure. That is, at the end of the deposition of each single Ni layer, air is let to flow into the vacuum chamber through a leak valve. Then, a very thin NiO layer ({approx}1.2 nm) is formed. Simulated x-ray reflectivity patterns reveal that layering is excellent for individual Ni-layer thickness larger than 2.5 nm, which is attributed to the intercalation of amorphous NiO between the polycrystalline Ni layers. The magnetization of the films, measured at temperatures 5-300 K, has almost bulk-like value, whereas the films exhibit a trend to perpendicular magnetic anisotropy (PMA) with an unusual significant positive interface anisotropy contribution, which presents a weak temperature dependence. The power-law behavior of the multilayers indicates a non-negligible contribution of higher order anisotropies in the uniaxial anisotropy. Bloch-law fittings for the temperature dependence of the magnetization in the spin-wave regime show that the magnetization in the multilayers decreases faster as a function of temperature than the one of bulk Ni. Finally, when the individual Ni-layer thickness decreases below 2 nm, the multilayer stacking vanishes, resulting in a dramatic decrease of the interface magnetic anisotropy and consequently in a decrease of the perpendicular magnetic anisotropy.
Pappas, S. D.; Trachylis, D.; Velgakis, M. J. [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Kapaklis, V.; Joensson, P. E.; Papaioannou, E. Th. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden); Delimitis, A. [Chemical Process Engineering Research Institute (CPERI), Centre for Research and Technology Hellas (CERTH), 57001 Thermi, Thessaloniki (Greece); Poulopoulos, P. [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin-Dahlem (Germany); Materials Science Department, University of Patras, 26504 Patras (Greece); Fumagalli, P. [Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin-Dahlem (Germany); Politis, C. [Laboratory of High-Tech Materials, School of Engineering, University of Patras, 26504 Patras (Greece); Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, Texas 76019 (United States)
Transient Peak Currents in Permanent Magnet Synchronous Motors
Transient Peak Currents in Permanent Magnet Synchronous Motors for Symmetrical Short Circuits Terms-- Permanent magnet synchronous motor, short circuit, protection measure, transient behavior I 33095 Paderborn, Germany Abstract--To enable constant-power areas with permanent magnet synchronous
Comparison of quantum-mechanical and semiclassical approaches for an analysis of spin dynamics in quantum dots
Two approaches to the description of spin dynamics of electron-nuclear system in quantum dots are compared: the quantum-mechanical one is based on direct diagonalization of the model Hamiltonian and semiclassical one is based on coupled equations for precession of mean electron spin and mean spin of nuclear spin fluctuations. The comparison was done for a model problem describing periodic excitation of electron-nuclear system by optical excitation. The computation results show that scattering of parameters related to fluctuation of the nuclear spin system leads to appearance of an ordered state in the system caused by periodic excitation and to the effect of electron-spin mode locking in an external magnetic field. It is concluded that both models can qualitatively describe the mode-locking effect, however give significantly different quantitative results. This may indicate the limited applicability of the precession model for describing the spin dynamics in quantum dots in the presence of optical pumping.
Petrov, M. Yu., E-mail: firstname.lastname@example.com; Yakovlev, S. V. [Saint Petersburg State University (Russian Federation)
Dynamics of nuclear polarization in InGaAs quantum dots in a transverse magnetic field
The time-resolved Hanle effect is examined for negatively charged InGaAs/GaAs quantum dots. Experimental data are analyzed by using an original approach to separate behavior of the longitudinal and transverse components of nuclear polarization. This made it possible to determine the rise and decay times of each component of nuclear polarization and their dependence on transverse magnetic field strength. The rise and decay times of the longitudinal component of nuclear polarization (parallel to the applied field) were found to be almost equal (approximately 5 ms). An analysis of the transverse component of nuclear polarization shows that the corresponding rise and decay times differ widely and strongly depend on magnetic field strength, increasing from a few to tens of milliseconds with an applied field between 20 and 100 mT. Current phenomenological models fail to explain the observed behavior of nuclear polarization. To find an explanation, an adequate theory of spin dynamics should be developed for the nuclear spin system of a quantum dot under conditions of strong quadrupole splitting.
Verbin, S. Yu., E-mail: firstname.lastname@example.com; Gerlovin, I. Ya.; Ignatiev, I. V., E-mail: firstname.lastname@example.com; Kuznetsova, M. S.; Cherbunin, R. V. [St. Petersburg State University, Spin Optics Laboratory (Russian Federation); Flisinski, K.; Yakovlev, D. R.; Bayer, M. [Technische Universitaet Dortmund (Germany)
Feedback control of spin systems
The feedback stabilization problem for ensembles of coupled spin 1/2 systems is discussed from a control theoretic perspective. The noninvasive nature of the bulk measurement allows for a fully unitary and deterministic closed loop. The Lyapunov-based feedback design presented does not require spins that are selectively addressable. With this method, it is possible to obtain control inputs also for difficult tasks, like suppressing undesired couplings in identical spin systems.
Claudio Altafini
Spin MOSFETs as a basis for spintronics
This article reviews a recently proposed new class of spin transistors referred to as spin metal-oxide-semiconductor field-effect transistors (spin MOSFETs), and their integrated circuit applications. The fundamental device structures, operating principle, ... Keywords: MOSFETs, Spintronics, spin MOSFETs, spin transistors
Satoshi Sugahara; Masaaki Tanaka
Spin resonance strength calculations
In calculating the strengths of depolarizing resonances it may be convenient to reformulate the equations of spin motion in a coordinate system based on the actual trajectory of the particle, as introduced by Kondratenko, rather than the conventional one based on a reference orbit. It is shown that resonance strengths calculated by the conventional and the revised formalisms are identical. Resonances induced by radiofrequency dipoles or solenoids are also treated; with rf dipoles it is essential to consider not only the direct effect of the dipole but also the contribution from oscillations induced by it.
Much of our understanding of the atomic-scale magnetic structure and the dynamical properties of solids and liquids was gained from neutron-scattering studies. Elastic and inelastic neutron spectroscopy provided physicists with an unprecedented, detailed access to spin structures, magnetic-excitation spectra, soft-modes and critical dynamics at magnetic-phase transitions, which is unrivaled by other experimental techniques. Because the neutron has no electric charge, it is an ideal weakly interacting and highly penetrating probe of matter's inner structure and dynamics. Unlike techniques using photon electric fields or charged particles (e.g., electrons, muons) that significantly modify the local electronic environment, neutron spectroscopy allows determination of a material's intrinsic, unperturbed physical properties. The method is not sensitive to extraneous charges, electric fields, and the imperfection of surface layers. Because the neutron is a highly penetrating and non-destructive probe, neutron spectroscopy can probe the microscopic properties of bulk materials (not just their surface layers) and study samples embedded in complex environments, such as cryostats, magnets, and pressure cells, which are essential for understanding the physical origins of magnetic phenomena. Neutron scattering is arguably the most powerful and versatile experimental tool for studying the microscopic properties of the magnetic materials. The magnitude of the cross-section of the neutron magnetic scattering is similar to the cross-section of nuclear scattering by short-range nuclear forces, and is large enough to provide measurable scattering by the ordered magnetic structures and electron spin fluctuations. In the half-a-century or so that has passed since neutron beams with sufficient intensity for scattering applications became available with the advent of the nuclear reactors, they have became indispensable tools for studying a variety of important areas of modern science, ranging from large-scale structures and dynamics of polymers and biological systems, to electronic properties of today's technological materials. Neutron scattering developed into a vast field, encompassing many different experimental techniques aimed at exploring different aspects of matter's atomic structure and dynamics. Modern magnetic neutron scattering includes several specialized techniques designed for specific studies and/or particular classes of materials. Among these are magnetic reflectometry aimed at investigating surfaces, interfaces, and multilayers, small-angle scattering for the large-scale structures, such as a vortex lattice in a superconductor, and neutron spin-echo spectroscopy for glasses and polymers. Each of these techniques and many others offer exciting opportunities for examining magnetism and warrant extensive reviews, but the aim of this chapter is not to survey how different neutron-scattering methods are used to examine magnetic properties of different materials. Here, we concentrate on reviewing the basics of the magnetic neutron scattering, and on the recent developments in applying one of the oldest methods, the triple axis spectroscopy, that still is among the most extensively used ones. The developments discussed here are new and have not been coherently reviewed. Chapter 2 of this book reviews magnetic small-angle scattering, and modern techniques of neutron magnetic reflectometry are discussed in Chapter 3.
Spin Coherence at the Nanoscale: Polymer Surfaces and Interfaces
Breakthrough results were achieved during the reporting period in the areas of organic spintronics. (A) For the first time the giant magnetic resistance (GMR) was observed in spin valve with an organic spacer. Thus we demonstrated the ability of organic semiconductors to transport spin in GMR devices using rubrene as a prototype for organic semiconductors. (B) We discovered the electrical bistability and spin valve effect in a ferromagnet /organic semiconductor/ ferromagnet heterojunction. The mechanism of switching between conducting phases and its potential applications were suggested. (C) The ability of V(TCNE)x to inject spin into organic semiconductors such as rubrene was demonstrated for the first time. The mechanisms of spin injection and transport from and into organic magnets as well through organic semiconductors were elucidated. (D) In collaboration with the group of OSU Prof. Johnston-Halperin we reported the successful extraction of spin polarized current from a thin film of the organic-based room temperature ferrimagnetic semiconductor V[TCNE]x and its subsequent injection into a GaAs/AlGaAs light-emitting diode (LED). Thus all basic steps for fabrication of room temperature, light weight, flexible all organic spintronic devices were successfully performed. (E) A new synthesis/processing route for preparation of V(TCNE)x enabling control of interface and film thicknesses at the nanoscale was developed at OSU. Preliminary results show these films are higher quality and what is extremely important they are substantially more air stable than earlier prepared V(TCNE)x. In sum the breakthrough results we achieved in the past two years form the basis of a promising new technology, Multifunctional Flexible Organic-based Spintronics (MFOBS). MFOBS technology enables us fabrication of full function flexible spintronic devices that operate at room temperature.
Epstein, Arthur J. [Professor
Accretion-Powered Stellar Winds III: Spin Equilibrium Solutions
We compare the stellar wind torque calculated in a previous work (Paper II) to the spin-up and spin-down torques expected to arise from the magnetic interaction between a slowly rotating ($\\sim 10$% of breakup) pre-main-sequence star and its accretion disk. This analysis demonstrates that stellar winds can carry off orders of magnitude more angular momentum than can be transferred to the disk, provided that the mass outflow rates are greater than the solar wind. Thus, the equilibrium spin state is simply characterized by a balance between the angular momentum deposited by accretion and that extracted by a stellar wind. We derive a semi-analytic formula for predicting the equilibrium spin rate as a function only of the ratio of $\\dot M_{\\rm w} / \\dot M_{\\rm a}$ and a dimensionless magnetization parameter, $\\Psi \\equiv B_*^2 R_*^2 (\\dot M_{\\rm a} v_{\\rm esc})^{-1}$, where $\\dot M_{\\rm w}$ is the stellar wind mass outflow rate, $\\dot M_{\\rm a}$ the accretion rate, $B_*$ the stellar surface magnetic field strength, $R_*$ the stellar radius, and $v_{\\rm esc}$ the surface escape speed. For parameters typical of accreting pre-main-sequence stars, this explains spin rates of $\\sim 10$% of breakup speed for $\\dot M_{\\rm w} / \\dot M_{\\rm a} \\sim 0.1$. Finally, the assumption that the stellar wind is driven by a fraction of the accretion power leads to an upper limit to the mass flow ratio of $\\dot M_{\\rm w} / \\dot M_{\\rm a} \\la 0.6$.
Sean Matt; Ralph E. Pudritz
Separability and ground state factorization in quantum spin systems
We investigate the existence and the properties of fully separable (fully factorized) ground states in quantum spin systems. Exploiting techniques of quantum information and entanglement theory we extend a recently introduced method and construct a general, self-contained theory of ground state factorization in frustration-free quantum spin models defined on lattices in any spatial dimension and for interactions of arbitrary range. We show that, quite generally, non exactly solvable models in external field admit exact, fully factorized ground state solutions. Unentangled ground states occur at finite values of the Hamiltonian parameters satisfying well defined balancing conditions between external fields and interaction strengths. These conditions are analytically determined together with the type of magnetic orderings compatible with factorization and the corresponding values of the fundamental observables such as energy and magnetization. The method is applied to a series of examples of increasing complexi...
Giampaolo, S M; Illuminati, F
High-spin level scheme of {sup 194}Pb
High-spin states in {sup 194}Pb have been populated in the {sup 168}Er({sup 30}Si,4n) reaction at 142 MeV. The emitted {gamma} rays were detected by the EUROBALL III multidetector array. The level scheme was considerably extended and many previously observed {gamma}-ray transitions were reordered. Four new magnetic rotational bands were observed. The energies and spins of the bandheads of all previously observed magnetic rotational bands were corrected based on the observation of new transitions. From nine observed bands, only one could not be connected to the lower lying states. Based on comparison systematics with neighboring Pb isotopes and tilted-axis cranking model calculations previously reported, configuration assignments to the observed bands have been made.
Kutsarova, T.; Stefanova, E. A.; Minkova, A.; Lalkovski, S.; Korichi, A.; Lopez-Martens, A.; Hannachi, F.; Huebel, H.; Goergen, A.; Jansen, A.; Schoenwasser, G.; Khoo, T. L.; Herskind, B.; Bergstroem, M.; Bazzacco, D.; Podolyak, Z. [Institute for Nuclear Research and Nuclear Energy, BAS, BG-1784 Sofia (Bulgaria); Faculty of Physics, University of Sofia 'St. Kliment Ohridski', BG-1164 Sofia (Bulgaria); CSNSM Orsay, IN2P3/CNRS, F-91405 (France); HISKP, Helmholtz-Institute fuer Strahlen-und Kernphysik, Nussallee 14-16, D-53115 (Germany); ISKP, Universitaet Bonn, Nussallee 14-16, D-53115 (Germany); Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Dipartimento di Fisica, Universita di Padova and INFN Sezione di Padova, I-35131 Padova (Italy); INFN, Laboratori Nationali di Legnaro (Italy)
Depth Profile of Uncompensated Spins in an Exchange-Bias System
Depth Profile of Uncompensated Depth Profile of Uncompensated Spins in an Exchange-Bias System Depth Profile of Uncompensated Spins in an Exchange-Bias System Print Wednesday, 25 January 2006 00:00 The phenomenon known as exchange bias at the interface between a ferromagnet and an antiferromagnet is currently a subject of intense research because of its applications in the magnetic recording and read-head industries. An international collaboration headed by researchers from the University of California, San Diego, has used resonant x-ray scattering and polarized-neutron reflectometry to determine the depth-dependent magnetization in an exchange-biased sample. These results provide atomic-level insights into the mechanism of exchange bias, specifically the involvement of mutual interactions between two kinds of uncompensated spins in the antiferromagnet and spins in the ferromagnet.
Depth Profile of Uncompensated Spins in an Exchange-Bias System Print Depth Profile of Uncompensated Spins in an Exchange-Bias System Print The phenomenon known as exchange bias at the interface between a ferromagnet and an antiferromagnet is currently a subject of intense research because of its applications in the magnetic recording and read-head industries. An international collaboration headed by researchers from the University of California, San Diego, has used resonant x-ray scattering and polarized-neutron reflectometry to determine the depth-dependent magnetization in an exchange-biased sample. These results provide atomic-level insights into the mechanism of exchange bias, specifically the involvement of mutual interactions between two kinds of uncompensated spins in the antiferromagnet and spins in the ferromagnet.
Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization
One fundamental requirement for quantum computation is to perform universal manipulations of quantum bits at rates much faster than the qubit's rate of decoherence. Recently, fast gate operations have been demonstrated in logical spin qubits composed of two electron spins where the rapid exchange of the two electrons permits electrically controllable rotations around one axis of the qubit. However, universal control of the qubit requires arbitrary rotations around at least two axes. Here we show that by subjecting each electron spin to a magnetic field of different magnitude we achieve full quantum control of the two-electron logical spin qubit with nanosecond operation times. Using a single device, a magnetic field gradient of several hundred milliTesla is generated and sustained using dynamic nuclear polarization of the underlying Ga and As nuclei. Universal control of the two-electron qubit is then demonstrated using quantum state tomography. The presented technique provides the basis for single and potent...
Foletti, Sandra; Mahalu, Diana; Umansky, Vladimir; Yacoby, Amir; 10.1038/nphys1424
Spin Spectrometer at the ALS and APS
5 Spin Spectrometer at the ALS and APS-NIM/SRI07 Figure 3 Ancollected on Beamline 7 at the ALS is shown here. The photonSpin Spectrometer at the ALS and APS-NIM/SRI07 Spin
Tobin, James G; Lawrence Livermore National Laboratory; University of Missouri-Rolla; Boyd Technologies
Single spin asymmetries at CLAS
We present recent results from Jefferson Lab's CLAS detector on beam and target single-spin asymmetries in single pion electroproduction off unpolarized hydrogen and polarized NH 3 targets. Non-zero single-beam and single-target spin asymmetries are observed for the first time in semi-inclusive and exclusive pion production in hard-scattering kinematics.
Harut Avakian; Latifa Elouadrhiri
Using nanoscale transistors to measure single donor spins in semiconductors
We propose a technique for measuring the state of a single donor electron spin usinga field-effect transistor induced two-dimensional electron gas and electrically detected magnetic resonance techniques. The scheme is faciltated by hyperfine coupling to the donor nucleus. We analyze the potential sensitivity and outlne experimental reqiurements. Our measurement provides a single-shot, projective, and quantum non-demoltion measurement of an electron-encoded qubit state.
Sarovar, M.; Young, K. C.; Whaley, K. B.; Schenkel, Thomas
Holonomic quantum computation with electron spins in quantum dots
With the help of the spin-orbit interaction, we propose a scheme to perform holonomic single-qubit gates on the electron spin confined to a quantum dot. The manipulation is done in the absence (or presence) of an applied magnetic field. By adiabatic changing the position of the confinement potential, one can rotate the spin state of the electron around the Bloch sphere in semiconductor heterostructures. The dynamics of the system is equivalent to employing an effective non-Abelian gauge potential whose structure depends on the type of the spin-orbit interaction. As an example, we find an analytic expression for the electron spin dynamics when the dot is moved around a circular path (with radius R) on the two dimensional electron gas (2DEG) and show that all single-qubit gates can be realized by tuning the radius and orientation of the circular paths. Moreover, using the Heisenberg exchange interaction, we demonstrate how one can generate two-qubit gates by bringing two quantum dots near each other, yielding a scalable scheme to perform quantum computing on arbitrary N qubits. This proposal shows a way of realizing holonomic quantum computers in solid-state systems.
Golovach, Vitaly N. [Arnold Sommerfeld Center for Theoretical Physics and Center for Nanoscience Department of Physics, Ludwig-Maximilians-Universitaet, Theresienstrasse 37, D-80333 Munich (Germany); Borhani, Massoud [Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland); Department of Physics, University at Buffalo, SUNY, Buffalo, New York 14260-1500 (United States); Loss, Daniel [Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland)
Persistent spin currents in an elastic Landau system
We consider a neutral particle with permanent magnetic dipole moment in an elastic medium with the presence of a uniform distribution of screw dislocations interacting with a radial electric field. We show that the uniform distribution of dislocations plays the role of an effective uniform magnetic field, and obtain a spectrum of energy which depends on the Aharonov-Casher geometric phase [Y. Aharonov and A. Casher, Phys. Rev. Lett. 53, 319 (1984)]. Moreover, from the dependence of energy levels on the Aharonov-Casher geometric phase, we calculate the persistent spin currents in this elastic Landau system.
K. Bakke; C. Furtado
Debye-Hueckel theory for spin ice at low temperature
At low temperatures, spin ice is populated by a finite density of magnetic monopoles--pointlike topological defects with a mutual magnetic Coulomb interaction. We discuss the properties of the resulting magnetic Coulomb liquid in the framework of Debye-Hueckel theory, for which we provide a detailed context-specific account. We discuss both thermodynamical and dynamical signatures and compare Debye-Hueckel theory to experiment as well as numerics, including data for specific heat and AC susceptibility. We also evaluate the entropic Coulomb interaction that is present in addition to the magnetic one and show that it is quantitatively unimportant in the current compounds. Finally, we address the role of bound monopole anti-monopole pairs and derive an expression for the monopole mobility.
Castelnovo, C. [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP (United Kingdom); SEPnet and Hubbard Theory Consortium, Department of Physics, Royal Holloway University of London, Egham TW20 0EX (United Kingdom); Moessner, R. [Max-Planck-Institut fuer Physik komplexer Systeme, D-01187 Dresden (Germany); Sondhi, S. L. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)
Voltage tunability of single spin-states in a quantum dot
Single spins in the solid-state offer a unique opportunity to store and manipulate quantum information, and to perform quantum-enhanced sensing of local fields and charges. Optical control of these systems using techniques developed in atomic physics has yet to exploit all the advantages of the solid-state. We demonstrate voltage tunability of the spin energy levels in a single quantum dot by modifying how spins sense magnetic field. We find the in-plane g-factor varies discontinuously for electrons, as more holes are loaded onto the dot. In contrast, the in-plane hole g-factor varies continuously. The device can change the sign of the in-plane g-factor of a single hole, at which point an avoided crossing is observed in the two spin eigenstates. This is exactly what is required for universal control of a single spin with a single electrical gate.
Anthony J. Bennett; Matthew A. Pooley; Yameng Cao; Niklas Sk�ld; Ian Farrer; David A. Ritchie; Andrew J. Shields
Direct measurement of the spin gaps in a gated GaAs two-dimensional electron gas
. For the low-field regime where ?s destroyed by the disorder, and there is no spin-splitting for the magnetic field less than Bc. As shown in Figure 7, the �spin gap� measured by the conventional activation energy studies... linearly to zero at a critical magnetic field Bc ~ 3.47 T. The spin gap is expected to have the form ?s = g0?BB + Eex = g * ?BB [12], where Eex is the many-body exchange energy which lifts the g-factor from its bare value (0.44 in GaAs) to its enhanced...
Huang, Tsai-Yu; Liang, Chi-Te; Chen, Yang Fang; Simmons, Michelle Y; Kim, Gil-Ho; Ritchie, David A
Effect of gate-driven spin resonance on the conductance of a one-dimensional quantum wire
We consider quasiballistic electron transmission in a one-dimensional quantum wire subject to both time-independent and periodic potentials of a finger gate that results in a coordinate- and time-dependent Rashba-type spin-orbit coupling. A spin-dependent conductance is calculated as a function of external constant magnetic field, the electric field frequency, and the potential strength. The results demonstrate the effect of the gate-driven electric dipole spin resonance in a transport phenomenon such as spin-flip electron transmission.
Almas F. Sadreev; E. Ya. Sherman
Recent Development in Proton Spin Physics
Development in Proton Spin Physics Feng YUAN [8] H. Jackson,investigations. These important physics, together with otherthat the transverse spin physics is playing a very important
Yuan, Feng
X-Ray Diffraction Microscopy of Magnetic Structures
X-Ray Diffraction Microscopy of Magnetic Structures Print X-Ray Diffraction Microscopy of Magnetic Structures Print science brief icon Scientists working at ALS Beamline 126.96.36.199 have demonstrated a new x-ray technique for producing short-exposure nanoscale images of the magnetic structure of materials. The new method combines aspects of coherent x-ray diffraction, which can determine 3-D charge distributions, and resonant magnetic scattering, which is sensitive to magnetic structures. Physicists have used coherent x-ray diffraction to measure the electron density of complicated molecules. The formula used to make these calculations contains terms that relate to the electron spin of magnetic atoms, but these terms are traditionally ignored since coherent x-ray diffraction has not been used to retrieve magnetic information. Using the full formula allows for the determination of not only the electron density, but also the magnetic spin distribution and its orientation.
Lensless Imaging of Magnetic Nanostructures
Lensless Imaging of Magnetic Lensless Imaging of Magnetic Nanostructures Lensless Imaging of Magnetic Nanostructures Print Wednesday, 28 March 2012 00:00 Magnetism is useful for many devices and techniques, from electric motors and computer hard drives to magnetic resonance imaging used in medicine. By studying the basics of magnetism, scientists aim to better understand the fundamental physical principles that govern magnetic systems, perhaps leading to important new technologies. The high brightness and coherence of the ALS's soft x-rays have enabled scientists to apply lensless x-ray imaging for the first time to nanometer-scale magnetic structures in an alloy. Many Ways To See You open your eyes and detect the light rays streaming through your bedroom window (transmission), illuminating your socks on the floor (scattering). You put on your glasses (refraction) to detect the state of your image in the mirror (reflection). If you are an ALS scientist, perhaps you go to work and shine some x-ray light on a crystal to detect the arrangement of the atoms in the crystal (diffraction). Now, thanks to Turner et al., you can also shine some x-ray light on a magnetic sample to detect the arrangement of its electron spins through a method known as lensless imaging. This last example is an equally valid way to "see," but instead of using windows, lenses, or mirrors to manipulate light and construct an image, mathematical formulas are used to describe the effects that particles and fields in the sample have on the light. These formulas have always contained terms that relate to the electron spin of magnetic atoms, but they were previously ignored. Using the full formula allows for the determination of not only crystal structure, but magnetic spin distribution and orientation as well, with a spatial resolution limited only by the wavelength of x-rays used. This promising method can be used at any coherent light source, including modern x-ray free-electron lasers, where ultrashort pulses would freeze-frame magnetic changes, offering the potential for imaging in unprecedented detail the structure and motion of boundaries between regions with different magnetic orientation.
Control of the direction and rate of nuclear spin flips in InAs quantum dots using detuned optical pulse trains
We find that detuning an optical pulse train from electronic transitions in quantum dots controls the direction of nuclear spin flips. The optical pulse train generates electron spins that precess about an applied magnetic field, with a spin component parallel to the field only for detuned pulses. This component leads to asymmetry in the nuclear spin flips, providing a way to produce a stable and precise value of the nuclear spin polarization. This effect is observed using two-color, time-resolved Faraday rotation and ellipticity.
S. G. Carter; A. Shabaev; Sophia E. Economou; T. A. Kennedy; A. S. Bracker; T. L. Reinecke
Theory of magnetization transport in a spatially varying magnetic field derived from entropic considerations
A theory of magnetization transport of a single spin-species in a spatially varying magnetic field is derived from entropic considerations. The theory describes thermodynamic transport in the language of differential geometry. Both magnetization diffusion and separation are predicted from a sample geometry, a magnetic field geometry, an entropy density function, and a single space-time scale. It is expressed first and most generally as coupled nonlinear partial differential equations, which are valid for the regime of high dipole-energy and magnetization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the SMT parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is derived, and is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield. Differences among the three models are illustrated by numerical solution. A family of analytic, steady-state solutions to the nonlinear transport equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. A steady-state solution for the magnetization is shown to be equivalent to the widely applied separation equation of Fenske. Moreover, we show that the SMT parameter is functionally related to the relative volatility parameter of Fenske.
Rico A. R. Picone; Joseph L. Garbini; John A. Sidles
Spin-1 atoms in optical superlattices: Single-atom tunneling and entanglement
We examine spinor Bose-Einstein condensates in optical superlattices theoretically using a Bose-Hubbard Hamiltonian that takes spin effects into account. Assuming that a small number of spin-1 bosons is loaded in an optical potential, we study single-particle tunneling that occurs when one lattice site is ramped up relative to a neighboring site. Spin-dependent effects modify the tunneling events in a qualitative and quantitative way. Depending on the asymmetry of the double well, different types of magnetic order occur, making the system of spin-1 bosons in an optical superlattice a model for mesoscopic magnetism. We use a double-well potential as a unit cell for a one-dimensional superlattice. Homogeneous and inhomogeneous magnetic fields are applied, and the effects of the linear and the quadratic Zeeman shifts are examined. We also investigate the bipartite entanglement between the sites and construct states of maximal entanglement. The entanglement in our system is due to both orbital and spin degrees of freedom. We calculate the contribution of orbital and spin entanglements and show that the sum of these two terms gives a lower bound for the total entanglement.
Wagner, Andreas; Bruder, Christoph; Demler, Eugene [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)
Investigation of the field-induced ferromagnetic phase transition in spin-polarized neutron matter: A lowest order constrained variational approach
In this article, the lowest order constrained variational method is used to investigate the magnetic properties of spin-polarized neutron matter in the presence of strong magnetic field at zero temperature employing the AV{sub 18} potential. Our results indicate that a ferromagnetic phase transition is induced by a strong magnetic field with strength greater than 10{sup 18} G, leading to a partial spin polarization of the neutron matter. It is also shown that the equation of state of neutron matter in the presence of a magnetic field is stiffer than in the absence of a magnetic field.
Bordbar, G. H. [Department of Physics, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha, P.O. Box 55134-441, Maragha 55177-36698 (Iran, Islamic Republic of); Rezaei, Z.; Montakhab, Afshin [Department of Physics, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)
Many-body Interactions in Magnetic Films and Nanostructures
We describe results supported by DOE grant DE-FG02-04ER46158, which focused on magnetic interaction at surfaces, in thin films, and in metallic nanostructures. We report on three general topics: 1) The Rashba spin splitting at magnetic surfaces of rare earth metals, 2) magnetic nanowires self-assembled on stepped tungsten single crystals, and 3) magnetic interaction in graphene films doped with hydrogen atoms.
Stephen D. Kevan
Electronic structure and magnetic properties of FeWO{sub 4} nanocrystals synthesized by the microwave-hydrothermal method
This communication reports that FeWO{sub 4} nanocrystals were successfully synthesized by the microwave-hydrothermal method at 443 K for 1 h. The structure and shape of these nanocrystals were characterized by X-ray diffraction, Rietveld refinement, and transmission electron microscopy. The experimental results and first principles calculations were combined to explain the electronic structure and magnetic properties. Experimental data were obtained by magnetization measurements for different applied magnetic fields. Theoretical calculations revealed that magnetic properties of FeWO{sub 4} nanocrystals can be assigned to two magnetic orderings with parallel or antiparallel spins in adjacent chains. These factors are crucial to understanding of competition between ferro- and antiferromagnetic behavior. Highlights: Black-Right-Pointing-Pointer Monophasic FeWO{sub 4} nanocrystals were synthesized by the microwave-hydrothermal method. Black-Right-Pointing-Pointer Rietveld refinement and clusters model for monoclinic structure Black-Right-Pointing-Pointer Magnetic properties of FeWO{sub 4} nanocrystals at different temperatures.
Almeida, M.A.P. [INCTMN-DQ-Universidade Federal de Sao Carlos, Sao Carlos, P.O. Box 676, 13565-905, SP (Brazil)] [INCTMN-DQ-Universidade Federal de Sao Carlos, Sao Carlos, P.O. Box 676, 13565-905, SP (Brazil); Cavalcante, L.S., E-mail: firstname.lastname@example.com [INCTMN-Universidade Estadual, Paulista, P.O. Box 355, 14801-907, Araraquara, SP (Brazil); Morilla-Santos, C.; Filho, P.N. Lisboa [MAv-Universidade Estadual, Paulista, P.O. Box 473, 17033-360, Bauru, SP (Brazil)] [MAv-Universidade Estadual, Paulista, P.O. Box 473, 17033-360, Bauru, SP (Brazil); Beltran, A.; Andres, J.; Gracia, L. [Department de Quimica Fisica i Analitica, Universitat Jaume I, E-12071 Castello (Spain)] [Department de Quimica Fisica i Analitica, Universitat Jaume I, E-12071 Castello (Spain); Longo, E. [INCTMN-DQ-Universidade Federal de Sao Carlos, Sao Carlos, P.O. Box 676, 13565-905, SP (Brazil) [INCTMN-DQ-Universidade Federal de Sao Carlos, Sao Carlos, P.O. Box 676, 13565-905, SP (Brazil); INCTMN-Universidade Estadual, Paulista, P.O. Box 355, 14801-907, Araraquara, SP (Brazil)
Lensless Imaging of Magnetic Nanostructures Print Lensless Imaging of Magnetic Nanostructures Print Magnetism is useful for many devices and techniques, from electric motors and computer hard drives to magnetic resonance imaging used in medicine. By studying the basics of magnetism, scientists aim to better understand the fundamental physical principles that govern magnetic systems, perhaps leading to important new technologies. The high brightness and coherence of the ALS's soft x-rays have enabled scientists to apply lensless x-ray imaging for the first time to nanometer-scale magnetic structures in an alloy. Many Ways To See You open your eyes and detect the light rays streaming through your bedroom window (transmission), illuminating your socks on the floor (scattering). You put on your glasses (refraction) to detect the state of your image in the mirror (reflection). If you are an ALS scientist, perhaps you go to work and shine some x-ray light on a crystal to detect the arrangement of the atoms in the crystal (diffraction). Now, thanks to Turner et al., you can also shine some x-ray light on a magnetic sample to detect the arrangement of its electron spins through a method known as lensless imaging. This last example is an equally valid way to "see," but instead of using windows, lenses, or mirrors to manipulate light and construct an image, mathematical formulas are used to describe the effects that particles and fields in the sample have on the light. These formulas have always contained terms that relate to the electron spin of magnetic atoms, but they were previously ignored. Using the full formula allows for the determination of not only crystal structure, but magnetic spin distribution and orientation as well, with a spatial resolution limited only by the wavelength of x-rays used. This promising method can be used at any coherent light source, including modern x-ray free-electron lasers, where ultrashort pulses would freeze-frame magnetic changes, offering the potential for imaging in unprecedented detail the structure and motion of boundaries between regions with different magnetic orientation.
Spin-manipulating polarized deuterons
Spin dynamics of polarized deuteron beams near depolarization resonances, including a new polarization preservation concept based on specially-designed multiple resonance crossings, has been tested in a series of experiments in the COSY synchrotron. Intricate spin dynamics with sophisticated pre-programmed patterns as well as effects of multiple crossings of a resonance were studied both theoretically and experimentally with excellent agreement. Possible applications of these results to preserve, manipulate and spin-flip polarized beams in synchrotrons and storage rings are discussed.
Morozov, V S; Krisch, A D; Leonova, M A; Raymond, R S; Sivers, D W; Wong, V K; Hinterberger, F; Kondratenko, A M
Quantum-mechanical description of spin-1 particles with electric dipole moments
The Proca-Corben-Schwinger equations for a spin-1 particle with an anomalous magnetic moment are added by a term describing an electric dipole moment, then they are reduced to a Hamiltonian form, and finally they are brought to the Foldy-Wouthuysen representation. Relativistic equations of motion are derived. The needed agreement between quantum-mechanical and classical relativistic equations of motion is proved. The scalar and tensor electric and magnetic polarizabilities of pointlike spin-1 particles (W bosons) are calculated for the first time.
Magnetic Systems Mimic Granular Materials | U.S. DOE Office of...
Office of Science (SC) Website
behavior of magnetic domain fluctuations near phase transitions will enable the control of the noise levels and help to improve the performance of future magnetic...
Electron Fabry-Perot interferometer with two entangled magnetic impurities
We consider a one-dimensional (1D) wire along which single conduction electrons can propagate in the presence of two spin-1/2 magnetic impurities. The electron may be scattered by each impurity via a contact-exchange interaction and thus a spin-flip generally occurs at each scattering event. Adopting a quantum waveguide theory approach, we derive the stationary states of the system at all orders in the electron-impurity exchange coupling constant. This allows us to investigate electron transmission for arbitrary initial states of the two impurity spins. We show that for suitable electron wave vectors, the triplet and singlet maximally entangled spin states of the impurities can respectively largely inhibit the electron transport or make the wire completely transparent for any electron spin state. In the latter case, a resonance condition can always be found, representing an anomalous behaviour compared to typical decoherence induced by magnetic impurities. We provide an explanation for these phenomena in term...
Ciccarello, F; Palma, G M; Vieira, V R; Zarcone, M
Pulsed Electrical Spin Injection into InGaAs Quantum Dots: Studies of the Electroluminescence Polarization Dynamics
We present time-resolved studies of the spin polarization dynamics during and after initialization through pulsed electrical spin injection into InGaAs quantum dots embedded in a p-i-n-type spin-injection light-emitting diode. Experiments are performed with pulse widths in the nanosecond range and a time-resolved single photon counting setup is used to detect the subsequent electroluminescence. We find evidence that the achieved spin polarization shows an unexpected temporal behavior, attributed mainly to many-carrier and non-equilibrium effects in the device.
Asshoff, P.; Loeffler, W.; Fluegge, H.; Zimmer, J.; Mueller, J.; Westenfelder, B.; Hu, D. Z.; Schaadt, D. M.; Kalt, H.; Hetterich, M. [Institut fuer Angewandte Physik and DFG Center for Functional Nanostructures (CFN), Universitaet Karlsruhe, 76131 Karlsruhe (Germany)
Kinetics of spin relaxation in quantum wires and channels: Boundary spin echo and formation of a persistent spin helix
In this paper we use a spin kinetic equation to study spin-polarization dynamics in one-dimensional (1D) wires and 2D channels. The spin kinetic equation is valid in both diffusive and ballistic spin transport regimes and therefore is more general than the usual spin drift-diffusion equations. In particular, we demonstrate that in infinite 1D wires with Rashba spin-orbit interaction the exponential spin-relaxation decay can be modulated by an oscillating function. In the case of spin relaxation in finite length 1D wires, it is shown that an initially homogeneous spin polarization spontaneously transforms into a persistent spin helix. We find that a propagating spin-polarization profile reflects from a system boundary and returns back to its initial position similarly to the reflectance of sound waves from an obstacle. The Green's function of the spin kinetic equation is derived for both finite and infinite 1D systems. Moreover, we demonstrate explicitly that the spin relaxation in specifically oriented 2D channels with Rashba and Dresselhaus spin-orbit interactions of equal strength occurs similarly to that in 1D wires of finite length. Finally, a simple transformation mapping 1D spin kinetic equation into the Klein-Gordon equation with an imaginary mass is found thus establishing an interesting connection between semiconductor spintronics and relativistic quantum mechanics.
Slipko, Valeriy A. [Department of Physics and Astronomy and USC Nanocenter, University of South Carolina, Columbia, South Carolina 29208 (United States); Department of Physics and Technology, V. N. Karazin Kharkov National University, Kharkov 61077 (Ukraine); Pershin, Yuriy V. [Department of Physics and Astronomy and USC Nanocenter, University of South Carolina, Columbia, South Carolina 29208 (United States)
Determination of rotatable and frozen CoO spins and their relationship to exchange bias in CoO/Fe/Ag(001)
The exchange bias of epitaxially grown CoO/Fe/Ag(001) was investigated using X-ray Magnetic Circular Dichroism (XMCD) and X-ray Magnetic Linear Dichroism (XMLD) techniques. A direct XMLD measurement on the CoO layer during the Fe magnetization reversal shows that the CoO compensated spins are rotatable at thinner thickness and frozen, i.e. fixed in direction to the lattice, at larger thickness. By a quantitative determination of the rotatable and frozen CoO spins as a function of the CoO film thickness, we find the remarkable result that the exchange bias is well established before frozen spins are detectable in the CoO film, contrary to the common assumption that the majority of antiferromagnetic spins need to be frozen to generate the exchange bias. We further show that the rotatable/frozen CoO spins are uniformly distributed in the CoO film.
Wu, J.; Park, J.; Kim, W.; Arenholz, E.; Liberati, M.; Scholl, A.; Wu, Y.; Hwang, C.; Qiu, Z.
Applications of highly spin-polarized xenon in NMR
The main goal of the work presented in this thesis is produce highly spin-polarized xenon to create much greater signal intensities (up to 54,000 times greater) so as to allow studies to be made on systems with low surface area and long spin-lattice relaxation times. The spin-exchange optical pumping technique used to create high nuclear spin polarization is described in detail in chapter two. This technique is initially applied to some multiple-pulse optically detected NMR experiments in low magnetic field (50G) that allow the study of quadrupoler interactions with a surface of only a few square centimeters. In chapter three the apparatus used to allow high field {sup 129}Xe NMR studies to be performed with extremely high sensitivity is described and applied to experiments on diamagnetic susceptibility effects in thin ({approximately}2000 layers) films of frozen xenon. Preliminary surface investigations of laser polarized {sup 129}Xe adsorbed an a variety of materials (salts, molecular crystals, amorphous carbon, graphite) are then discussed. A full detailed study of the surface of a particular polymer, poly(acrylic acid), is presented in chapter four which shows the kind of detailed information that can be obtained from this technique. Along with preliminary results for several similar polymers, a summary is given of xenon studies of a novel ultra-high surface area polymer, poly(triarylcarbinol). Finally in chapter five the exciting possibility of transferring the high spin order of the laser polarized xenon has been used to transfer nuclear spin order to {sup 13}CO{sub 2} in a xenon matrix and to protons on poly(triarylcarbinol).
Long, H.W. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States)
Reversing the Circulation of Magnetic Vortices Print Reversing the Circulation of Magnetic Vortices Print In magnetic media, information is stored in binary form-one or zero, depending on which way the electronic spins are aligned in a given section of the medium. Recently, however, magnetic vortices have drawn scientists toward a new possibility: multibit storage in which each logic unit has four states instead of two and can store twice the information. Each tiny magnetic whirl has a polarity that can point up or down and a circulation that can be oriented clockwise or counterclockwise. Previous studies have shown that the polarity can be flipped on command. Now, using time-resolved magnetic soft x-ray microscopy at the ALS, researchers have shown for the first time how to use pulsed magnetic fields to reverse the circulation.
Reversing the Circulation of Reversing the Circulation of Magnetic Vortices Reversing the Circulation of Magnetic Vortices Print Wednesday, 31 July 2013 00:00 In magnetic media, information is stored in binary form-one or zero, depending on which way the electronic spins are aligned in a given section of the medium. Recently, however, magnetic vortices have drawn scientists toward a new possibility: multibit storage in which each logic unit has four states instead of two and can store twice the information. Each tiny magnetic whirl has a polarity that can point up or down and a circulation that can be oriented clockwise or counterclockwise. Previous studies have shown that the polarity can be flipped on command. Now, using time-resolved magnetic soft x-ray microscopy at the ALS, researchers have shown for the first time how to use pulsed magnetic fields to reverse the circulation.
Magnetic Confinement Fusion Science Status and Challenges
by centrifugal force of particles moving along curved magnetic field plasma magnetic field Centrifugal force #12;Centrifugal force in a torus centrifugal force magnetic field #12;Stability theory is highly developed disruption to occur, Control its behavior by rapid injection of jet of neutral gas Causes energy
Superconducting Magnets
magnet technology has allowed physicists to attain higher energies in circular accelerators. One can obtain higher magnetic fields because there is no resistance in a...
Low-magnetic-field magnetars
It is now widely accepted that soft gamma repeaters and anomalous X-ray pulsars are the observational manifestations of magnetars, i.e. sources powered by their own magnetic energy. This view was supported by the fact that these `magnetar candidates' exhibited, without exception, a surface dipole magnetic field (as inferred from the spin-down rate) in excess of the electron critical field (~4.4E+13 G). The recent discovery of fully-qualified magnetars, SGR 0418+5729 and Swift J1822.3-1606, with dipole magnetic field well in the range of ordinary radio pulsars posed a challenge to the standard picture, showing that a very strong field is not necessary for the onset of magnetar activity (chiefly bursts and outbursts). Here we summarize the observational status of the low-magnetic-field magnetars and discuss their properties in the context of the mainstream magnetar model and its main alternatives.
Turolla, R
Large magnetoresistance in oxide based ferromagnet/superconductor spin switches.
We report large magnetoresistance (in excess of 1000%) in ferromagnet / superconductor / ferromagnet structures made of La{sub 0.7}Ca{sub 0.3}MnO{sub 3} and YBa{sub 2}Cu{sub 3}O{sub 7} in the current in plane (CIP) geometry. This magnetoresistance has many of the ingredients of the giant magnetoresistance of metallic superlattices: it is independent on the angle between current and magnetic field, depends on the relative orientation of the magnetization in the ferromagnetic layers, and takes very large values. The origin is enhanced scattering at the F/S interface in the anti parallel configuration of the magnetizations. Furthermore, we examine the dependence of the magnetoresistance effect on the thickness of the superconducting layer, and show that the magnetoresistance dies out for thickness in excess of 30 nm, setting a length scale for the diffusion of spin polarized quasiparticles.
Pena, V.; Nemes, N.; Visani, C.; Garcia-Barriocanal, J.; Bruno, F.; Arias, D.; Sefrioui, Z.; Leon, C.; te Velthuis, S. G. E.; Hoffmann, A.; Garcia-Hernandez, M.; Santamaria, J.; Materials Science Division; Univ. Complutense de Madrid; Inst. de Ciencia de Materiales de Madrid
Magnetism and Superconductivity in Iron Pnictides
The discovery of high temperature superconductivity in iron pnictides and chalcogenides has resulted in surprising new insights into high temperature superconductivity and its relationship with magnetism. Here we provide an overview of some of what is known about these materials and in particular about the interplay of magnetism and superconductivity in them. Similarities and contrasts with cuprate superconductors are emphasized and the superconducting pairing is discussed within the framework of spin fluctuation induced pairing.
Singh, David J [ORNL
Giant magnetoresistance in nanogranular magnets.
We study the giant magnetoresistance of nanogranular magnets in the presence of an external magnetic field and finite temperature. We show that the magnetization of arrays of nanogranular magnets has hysteretic behavior at low temperatures leading to a double peak in the magnetoresistance which coalesces at high temperatures into a single peak. We numerically calculate the magnetization of magnetic domains and the motion of domain walls in this system using a combined mean-field approach and a model for an elastic membrane moving in a random medium, respectively. From the obtained results, we calculate the electric resistivity as a function of magnetic field and temperature. Our findings show excellent agreement with various experimental data.
Glatz, A.; Beloborodov, I. S.; Vinokur, V. M.; Materials Science Division; Univ. of Chicago
Effects of thermal and quantum fluctuations on the phase diagram of a spin-1 {sup 87}Rb Bose-Einstein condensate
We investigate the effects of thermal and quantum fluctuations on the phase diagram of a spin-1 {sup 87}Rb Bose-Einstein condensate (BEC) under the quadratic Zeeman effect. Due to the large ratio of spin-independent to spin-dependent interactions of {sup 87}Rb atoms, the effect of noncondensed atoms on the condensate is much more significant than that in scalar BECs. We find that the condensate and spontaneous magnetization emerge at different temperatures when the ground state is in the broken-axisymmetry phase. In this phase, a magnetized condensate induces spin coherence of noncondensed atoms in different magnetic sublevels, resulting in temperature-dependent magnetization of the noncondensate. We also examine the effect of quantum fluctuations on the order parameter at absolute zero and find that the ground-state phase diagram is significantly altered by quantum depletion.
Phuc, Nguyen Thanh; Kawaguchi, Yuki [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Ueda, Masahito [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); ERATO Macroscopic Quantum Control Project, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
Nuclear Magnetism and Electronic Order in 13 C Nanotubes
Nuclear Magnetism and Electronic Order in 13 C Nanotubes Bernd Braunecker,1 Pascal Simon,1 on nuclear magnetism in one dimension. If the electrons are in the metallic, Luttinger liquid regime, we show that even a very weak hyperfine coupling to the 13C nuclear spins has a striking effect: The system
Braunecker, Bernd
Estimation of a classical parameter with gaussian probes: magnetometry with collective atomic spins
We present a theory for the estimation of a classical magnetic field by an atomic sample with a gaussian distribution of collective spin components. By incorporating the magnetic field and the probing laser field as quantum variables with gaussian distributions on equal footing with the atoms, we obtain a very versatile description which is readily adapted to include probing with squeezed light, dissipation and loss and additional measurement capabilities on the atomic system.
Klaus Molmer; Lars Bojer Madsen
Spin hall effect in paramagnetic thin films
Spintronics, an abbreviation of spin based electronics and also known as magneto electronics, has attracted a lot of interest in recent years. It aims to explore the role of electrons� spins in building next generation electric devices. Using electrons� spins rather than electrons� charges may allow faster, lower energy cost devices. Spin Hall Effect is an important subfield of spintronics. It studies spin current, spin transport, and spin accumulation in paramagnetic systems. It can further understanding of quantum physics, device physics, and may also provide insights for spin injection, spin detection and spin manipulation in the design of the next generation spintronics devices. In this experimental work, two sets of experiments were prepared to detect the Spin Hall Effect in metallic systems. The first set of experiments aims to extract Spin Hall Effect from Double Hall Effect in micrometer size metal thin film patterns. Our experiments proved that the Spin Hall Effect signal was much smaller than the theoretically calculated value due to higher electrical resistivity in evaporated thin films. The second set of experiments employs a multi-step process. It combines micro fabrication and electrochemical method to fabricate a perpendicular ferromagnet rod as a spin injector. Process description and various techniques to improve the measurement sensitivity are presented. Measurement results in aluminum, gold and copper are presented in Chapters III, IV and V. Some new experiments are suggested in Chapters V and VI.
Xu, Huachun
Detection and Control of Individual Nuclear Spins Using a Weakly Coupled Electron Spin
We experimentally isolate, characterize, and coherently control up to six individual nuclear spins that are weakly coupled to an electron spin in diamond. Our method employs multipulse sequences on the electron spin that resonantly amplify the interaction with a selected nuclear spin and at the same time dynamically suppress decoherence caused by the rest of the spin bath. We are able to address nuclear spins with interaction strengths that are an order of magnitude smaller than the electron spin dephasing rate. Our results provide a route towards tomography with single-nuclear-spin sensitivity and greatly extend the number of available quantum bits for quantum information processing in diamond.
Taminiau, T.H.; Wagenaar, J.J.T.; van der Sar, T.; Jelezko, F.; Dobrovitski, Viatcheslav V.; Hanson, R.
Classically spinning and isospinning solitons
We investigate classically spinning topological solitons in (2+1)- and (3+1)-dimensional models; more explicitely spinning sigma model solitons in 2+1 dimensions and Skyrme solitons in 2+1 and 3+1 dimensions. For example, such types of solitons can be used to describe quasiparticle excitations in ferromagnetic quantum Hall systems or to model spin and isospin states of nuclei. The standard way to obtain solitons with quantised spin and isospin is the semiclassical quantization procedure: One parametrizes the zero-mode space - the space of energy-degenerate soliton configurations generated from a single soliton by spatial translations and rotations in space and isospace - by collective coordinates which are then taken to be time-dependent. This gives rise to additional dynamical terms in the Hamiltonian which can then be quantized following semiclassical quantization rules. A simplification which is often made in the literature is to apply a simple adiabatic approximation to the (iso)rotational zero modes of the soliton by assuming that the soliton's shape is rotational frequency independent. Our numerical results on classically spinning arbitrarily deforming soliton solutions clearly show that soliton deformation cannot be ignored.
Battye, Richard A.; Haberichter, Mareike [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom)
Hestenes' Tetrad and Spin Connections
Defining a spin connection is necessary for formulating Dirac's bispinor equation in a curved space-time. Hestenes has shown that a bispinor field is equivalent to an orthonormal tetrad of vector fields together with a complex scalar field. In this paper, we show that using Hestenes' tetrad for the spin connection in a Riemannian space-time leads to a Yang-Mills formulation of the Dirac Lagrangian in which the bispinor field is mapped to a set of Yang-Mills gauge potentials and a complex scalar field. This result was previously proved for a Minkowski space-time using Fierz identities. As an application we derive several different non-Riemannian spin connections found in the literature directly from an arbitrary linear connection acting on Hestenes' tetrad and scalar fields. We also derive spin connections for which Dirac's bispinor equation is form invariant. Previous work has not considered form invariance of the Dirac equation as a criterion for defining a general spin connection.
Frank Reifler; Randall Morris
-Interface effects on the magnetic moment of Co and Cu in CoCu granular alloys
We report on x-ray magnetic circular dichroism experiments performed on Co{sub 5}Cu{sub 95} annealed granular alloys with giant magnetoresistance. Results on the Co-L{sub 2,3} edge evidence a direct correlation between the Co orbital and spin magnetic moment and the Co clusters interfacial roughness. On the other hand, we have found dichroism on the Cu-L{sub 2,3} edge, revealing an induced magnetic polarization of the Cu interfacial atoms. The magnetic moment of the Cu atoms is mainly of spin character and is ferromagnetically coupled with the Co magnetic moment.
Garcia Prieto, A.; Fdez-Gubieda, M.L.; Chaboy, J.; Laguna-Marco, M.A.; Muro, T.; Nakamura, T. [Departamento de Electricidad y Electronica, Universidad del Pais Vasco (UPV/EHU), Apartado 644, 48080 Bilbao (Spain); Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain); CITIMAC, Universidad de Cantabria, Avenida de los Castros s/n, 39005 Santander (Spain); Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Mikazuki, Sayo, Hyogo 679-5148 (Japan)
A high-field adiabatic fast passage ultracold neutron spin flipper for the UCNA experiment
The UCNA collaboration is making a precision measurement of the {beta} asymmetry (A) in free neutron decay using polarized ultracold neutrons (UCN). A critical component of this experiment is an adiabatic fast passage neutron spin flipper capable of efficient operation in ambient magnetic fields on the order of 1 T. The requirement that it operate in a high field necessitated the construction of a free neutron spin flipper based, for the first time, on a birdcage resonator. The design, construction, and initial testing of this spin flipper prior to its use in the first measurement of A with UCN during the 2007 run cycle of the Los Alamos Neutron Science Center's 800 MeV proton accelerator is detailed. These studies determined the flipping efficiency of the device, averaged over the UCN spectrum present at the location of the spin flipper, to be {epsilon}=0.9985(4).
Holley, A. T.; Pattie, R. W.; Young, A. R. [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States); Broussard, L. J. [Department of Physics, Duke University, Durham, North Carolina 27708 (United States); Davis, J. L.; Ito, T. M.; Lyles, J. T. M.; Makela, M.; Morris, C. L.; Mortensen, R.; Saunders, A. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Hickerson, K.; Mendenhall, M. P. [W. K. Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125 (United States); Liu, C.-Y. [Department of Physics, Indiana University, Bloomington, Indiana 47405 (United States); Mammei, R. R. [Department of Physics, Virginia Tech, Blacksburg, Virginia 24061 (United States); Rios, R. [Department of Physics, Idaho State University, Pocatello, Idaho 83209 (United States)
Spin excitations in K2Fe4+xSe5: Linear response approach
Using ab initio linear response techniques we calculate spin-wave spectra in K2Fe4+xSe5, and find them to be in excellent agreement with a recent experiment. The spectrum can be described reasonably well by a localized spin Hamiltonian restricted to first and second nearest neighbor couplings. We confirm that exchange coupling between nearest neighbor Fe magnetic moments is strongly anisotropic, and show directly that in the ideal system this anisotropy has an itinerant nature which can be imitated by introducing higher order terms in the effective localized spin Hamiltonian (biquadratic coupling). In the real system, structural relaxation provides an additional source of the exchange anisotropy of approximately the same magnitude. The dependence of spin-wave spectra on the filling of Fe vacancy sites is also discussed.
Ke, Liqin; van Schilfgaarde, Mark; Antropov, Vladimir
Magnetized baryonic matter in holographic QCD
We investigate the properties of the Sakai-Sugimoto model at finite magnetic field and baryon chemical potentials. We show that in a finite magnetic field, there exists a spatially homogeneous configuration carrying finite baryon number density. At low magnetic field and baryon chemical potential the equation of state of the matter coincides with that obtained from the chiral perturbation theory Lagrangian with an anomalous term. We discuss the behavior of the system at larger magnetic fields.
Ethan G. Thompson; Dam T. Son
Ultra low power associative computing with spin neurons and resistive crossbar memory
Emerging resistive-crossbar memory (RCM) technology can be promising for computationally-expensive analog pattern-matching tasks. However, the use of CMOS analog-circuits with RCM would result in large power-consumption and poor scalability, thereby ... Keywords: emerging circuits and devices, magnets, memory, spin-transfer torque, spintronics
Mrigank Sharad, Deliang Fan, Kaushik Roy
PHYSICAL REVIEW A 81, 062353 (2010) Channel capacities of an exactly solvable spin-star system
, Islamabad 45320, Pakistan 2 Departments of Physics, Chemistry, and Electrical Engineering, Center memory plays a role [31,32]. Many quantum optical [33] and nuclear magnetic resonance systems [34-Markovian effects are especially important in condensed matter systems, such as coupled electron or nuclear spins
Lidar, Daniel
Argonne CNM Highlight: Biofunctionalized magnetic-vortex microdiscs for
Biofunctionalized magnetic-vortex microdiscs for targeted cancer-cell destruction Biofunctionalized magnetic-vortex microdiscs for targeted cancer-cell destruction Magnetic microdisks Reflection optical microscope image of a dried suspension of the discs prepared via magnetron sputtering and optical lithography. Magnetic spin vortex Model of magnetic-vortex spin distribution in a disc. Users from Argonne's Materials Science Division and University of Chicago's Pritzker School of Medicine, working collaboratively on a user science project with CNM's Nanobio Interfaces Group, have discovered that nanostructured magnetic materials offer exciting avenues for probing cell mechanics, activating mechanosensitive ion channels, and advancing potential cancer therapies. Their new report describes an approach based on interfacing cells with lithographically defined microdiscs (1-micron
Heavy Metals Behavior of Municiple Solid Waste Incineration ... - TMS
May 1, 2007 ... Heavy Metals Behavior of Municiple Solid Waste Incineration Bottom Ash with Magnetic Separation by Gi-Chun Han, Nam-Il Um, Kwang-Suk�...
Electronic and magnetic structures of the postperovskite-type Fe[subscript 2]O[subscript 3] and implications for planetary magnetic records and deep interiors
Recent studies have shown that high pressure (P) induces the metallization of the Fe[superscript 2+]�O bonding, the destruction of magnetic ordering in Fe, and the high-spin (HS) to low-spin (LS) transition of Fe in silicate ...
Shim, Sang-Heon Dan
Magnetic Structures
... Reentrant Spin-Glass Order Parameter in (Fe 0.3 Ni 0.7 ) 75 P 16 B ... JW Lynn, G. Bendele, S. Pagola, PW Stephens, LM Liable-Sands, AL Rheingold ...
During the summer of 2002, eight superconducting helical spin rotators were installed into RHIC in order to control the polarization directions independently at the STAR and PHENIX experiments. Without the rotators, the orientation of polarization at the interaction points would only be vertical. With four rotators around each of the two experiments, we can rotate either or both beams from vertical into the horizontal plane through the interaction region and then back to vertical on the other side. This allows independent control for each beam with vertical, longitudinal, or radial polarization at the experiment. In this paper, we present results from the first run using the new spin rotators at PHENIX.
Mackay, W W; Bai, M; Courant, E D; Fischer, W; Huang, H; Luccio, A; Montag, C; Pilat, F; Ptitsyn, V; Roser, T; Satogata, T; Trbojevic, D
Top Quark Spin Correlations - Theory
The top quark decay width (G{sub F}m{sub t}{sup 3} {approx} 1 GeV) is much larger than the QCD hadronization scale ({Lambda}{sub QCD} {approx} 0.1 GeV) and much larger than the spin decorrelation scale ({Lambda}{sub QCD}{sup 2}/m{sub t} {approx} 0.1 MeV). Therefore, spin correlations in top quark pair production are reflected in angular correlations of the decay products, see [1] and [2].
Parke, Stephen J.; /Fermilab
Software Model Checking with SPIN
The aim of this chapter is to give an overview ofthe theoretical foundation and the practical application of logic model checking techniques for the verification of multi-threaded software (rather than hardware) systems. The treatment is focused on the logic model checker SPIN, which was designed for this specific domain of application. SPIN implements an automata-theoretic method of verification. Although the tool has been available for over 15years, it continues to ev olve, adopting new optimization strategies from time to time to help it tackle larger verification problems. This chapter explains how the tool works, and
Gerard J. Holzmann
We investigate the existence and the properties of fully separable (fully factorized) ground states in quantum spin systems. Exploiting techniques of quantum information and entanglement theory we extend a recently introduced method and construct a general, self-contained theory of ground state factorization in frustration free quantum spin models defined on lattices in any spatial dimension and for interactions of arbitrary range. We show that, quite generally, non exactly solvable translationally invariant models in presence of an external uniform magnetic field can admit exact, fully factorized ground state solutions. Unentangled ground states occur at finite values of the Hamiltonian parameters satisfying well defined balancing conditions between the applied field and the interaction strengths. These conditions are analytically determined together with the type of magnetic orderings compatible with factorization and the corresponding values of the fundamental observables such as energy and magnetization. The method is applied to a series of examples of increasing complexity, including translationally-invariant models with short, long, and infinite ranges of interaction, as well as systems with spatial anisotropies, in low and higher dimensions. We also illustrate how the general method, besides yielding a large series of novel exact results for complex models in any dimension, recovers, as particular cases, the results previously achieved on simple models in low dimensions exploiting direct methods based on factorized mean-field ansatz.
S. M. Giampaolo; G. Adesso; F. Illuminati
Spin tracking in RHIC (Code Spink)
The evolution of the spin during acceleration in the Relativistic Heavy Ion Collider (RHIC) has been studied with a new numerical code, Spink. Results of spin tracking through resonances are shown.
Luccio, A.U.
Control of single spin in Markovian environment
In this article we study the control of single spin in Markovian environment. Given an initial state, we compute all the possible states to which the spin can be driven at arbitrary time, under the assumption that fast ...
Yuan, Haidong
Efficient Spin Injection using Tunnel Injectors
Semiconductor spintronics aims to develop novel sensor, memory and logic devices by manipulating the spin states of carriers in semiconducting materials. This talk will focus on electrical spin injection into semiconductors, which is a prerequisite for ...
Xin Jiang
Nucleon spin physics at Jefferson Lab
In this talk I shall review some of the important results from the spin physics program at JLab and give an outlook for the 12 GeV upgrade spin program.
Zein-Eddine Meziani
Spin liquids, exotic phases and phase transitions
Spin liquid, or featureless Mott-Insulator, is a theoretical state of matter firstly motivated from study on High-Tc superconductor. The most striking property of spin liquids is that they do not break any physical symmetry, ...
Ran, Ying
Spin injection into semiconductors : the role of Fe/Al[sub x]Ga[sub 1-x]As interface
The influence of the growth and post-growth annealing temperatures of Fe/Al{sub x}Ga{sub 1-x}As-based spin light-emitting diodes (LEDs) on the spin injection efficiency is discussed. The extent of interfacial reactions during molecular beam epitaxial growth of Fe on GaAs was determined from in-situ x-ray photoelectron spectroscopy studies. The Fe/GaAs interface results in {<=} 3 monolayers of reaction for Fe grown at -15 C. Intermediate growth temperatures (95 C) lead to {approx}5 monolayers of interfacial reactions, and high growth temperatures of 175 C lead to a {approx}9 monolayer thick reacted layer. Polarized neutron reflectivity was used to determine the interfacial magnetic properties of epitaxial Fe{sub 0.5}Co{sub 0.5}/GaAs heterostructures grown under identical conditions. No interfacial magnetic dead layer is detected at the interface for Fe{sub 0.5}Co{sub 0.5} films grown at -15 C, an {approx}6 {angstrom} thick nonmagnetic layer formed at the interface for 95 C growth and an {approx}5 {angstrom} thick magnetic interfacial reacted layer formed for growth at 175 C. Spin injection from Fe contacts into spin LEDs decreases sharply when reactions result in a nonmagnetic interfacial layer. Significant spin injection signals are obtained from Fe contacts grown between -5 C and 175 C, although the higher Fe growth temperatures resulted in a change in the sign of the spin polarization. Post-growth annealing of the spin LEDs is found to increase spin injection efficiency for low Fe growth temperatures and to a sign reversal of the spin polarization for high growth temperature (175 C). An effective Schottky barrier height increase indicates that post growth annealing modifies the Fe/Al{sub x}Ga{sub 1-x}As interface.
Fitzsimmons, M. R. (Michael R.); Park, S. (Sungkyun)
Magnetic Blockade Mechanism for Quantum Nucleation of Superconducting Vortex-Antivortex Pairs in Zero External Magnetic Field
We propose a magnetic dual of the Coulomb blockade effect for quantum nucleation of flux vortex pairs in high-Tc superconducting (HTS) films and grain boundaries in zero applied field. The magnetic blockade instability occurs at {\\theta} = {\\pi}, where {\\theta} is the "vacuum" or theta angle. The {\\theta} term has recently been discussed in the context of several other systems, including charge and spin density waves, topological insulators, the quantum Hall effect, and spontaneous CP violation. Our model predicts a sharp pair creation threshold current at {\\theta} = {\\pi}, analogous to the Coulomb blockade voltage of a tunnel junction, and explains the observed thickness dependence of critical currents in HTS coated conductors. We use the Schr\\"odinger equation to compute the evolving macrostate amplitudes, coupled by a generalized tunneling matrix element. The simulations yield excellent quantitative agreement with measured voltage-current characteristics of bi-crystal and other HTS grain boundary junctions. The model also predicts non-sinusoidal behavior in the voltage oscillations resulting from time-correlated vortex tunneling.
J. H. Miller Jr.; A. I. Wijesinghe
CNST Researchers Use Spin Waves to Measure Magnetic ...
... Recently, the use of giant magnetoresistance (GMR) in such sensors, with current flowing in the plane of a multilayer film, has given way to the use ...
... day material synthesis techniques for oxide materials were developed in part in the quest to fabricate high temperature superconductors, and has ...
NMR in rotating magnetic fields: Magic angle field spinning
to High- Resolution ex Situ NMR Spectroscopy�, Science, 293,A. Pines, �High- resolution NMR of biological tissues usingP. Mansfield and P. G. Morris, �NMR Imaging in Biomedicine�,
Sakellariou, D.; Meriles, C.; Martin, R.; Pines, A.
Electron Correlation and the Nuclear Spin�Spin Coupling Constant. I. An Alternant Molecular Orbital Description of Nuclear Spin�Spin Coupling
A theoretical description of contact nuclear spin�spin coupling is presented in terms of the density?matrix formalism and the approximation of an ``average excitation energy''. For a molecular system in a singlet state the density of spin coupling is proportional to the difference between the correlation functions for electrons of the same and opposite spins. Application of the one?parameter alternant molecular orbital (AMO) method
Michael Barfield
Spin-forming Project Report
In a second development order, spin-forming equipment was again evaluated using the test shape, a hemispherical shell. In this second development order, pure vanadium and alloy titanium (Ti-6Al-4V) were spin-formed, as well as additional copper and 21-6-9 stainless. In the first development order the following materials had been spin-formed: copper (alloy C11000 ETP), 6061 aluminum, 304L stainless steel, 21-6-9 stainless steel, and tantalum-2.5% tungsten. Significant challenges included properly adjusting the rotations-per-minute (RPM), cracking at un-beveled edges and laser marks, redressing of notches, surface cracking, non-uniform temperature evolution in the titanium, and cracking of the tailstock. Lessons learned were that 300 RPM worked better than 600 RPM for most materials (at the feed rate of 800 mm/min); beveling the edges to lower the stress reduces edge cracking; notches, laser marks, or edge defects in the preform doom the process to cracking and failure; coolant is required for vanadium spin-forming; increasing the number of passes to nine or more eliminates surface cracking for vanadium; titanium develops a hot zone in front of the rollers; and the tailstock should be redesigned to eliminate the cylindrical stress concentrator in the center.
Switzner, Nathan; Henry, Dick
Spin Transport and Relaxation in Graphene and Germanium
transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fig. 1-8, electrical spin transport in Si . . . . . . . . .21 Chapter 2: Theoretical view of spin transport and
Han, Wei
The optical models which may be used to describe the scattering and the possible forms of spin-orbit coupling are discussed. The scattering amplitudes are defined and described, including the effects of an isolated resonance, and used to give expressions for the differential cross section and polarization. The latter results are extended to include the change of polarization induced on scattering a polarized beam. Double scattering and the change in polarization produced by deflection in a magnetic field are described. A detailed discussion of possible tensor spinorbit couplings is given. (W.D.M.)
Satchler, G.R.
An Exact SU(2) Symmetry and Persistent Spin Helix ina Spin-orbit Coupled System
Spin-orbit coupled systems generally break the spin rotation symmetry. However, for a model with equal Rashba and Dresselhauss coupling constant (the ReD model), and for the [110] Dresselhauss model, a new type of SU(2) spin rotation symmetry is discovered. This symmetry is robust against spin-independent disorder and interactions, and is generated by operators whose wavevector depends on the coupling strength. It renders the spin lifetime infinite at this wavevector, giving rise to a Persistent Spin Helix (PSH). We obtain the spin fluctuation dynamics at, and away, from the symmetry point, and suggest experiments to observe the PSH.
Bernevig, B.A.; /Stanford U., Phys. Dept. /Santa Barbara, KITP; Orenstein, J.; /LBL, Berkeley /UC, Berkeley; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
An Exact SU(2) Symmetry and Persistent Spin Helix in a Spin-Orbit Coupled System
Bernevig, Andrei
'Spin Casting' And 'Cold Deformation'
Numerical Modeling of Centrifugally Cast HSS Rolls � Numerical Simulation of Electro-magnetic Turbulent Inhibitor Technology in a Tundish � Optimizing the�...
Proceedings of RIKEN BNL Research Center Workshop: Brookhaven Summer Program on Nucleon Spin Physics
Understanding the structure of the nucleon is of fundamental importance in sub-atomic physics. Already the experimental studies on the electro-magnetic form factors in the 1950s showed that the nucleon has a nontrivial internal structure, and the deep inelastic scattering experiments in the 1970s revealed the partonic substructure of the nucleon. Modern research focuses in particular on the spin and the gluonic structure of the nucleon. Experiments using deep inelastic scattering or polarized p-p collisions are carried out in the US at the CEBAF and RHIC facilities, respectively, and there are other experimental facilities around the world. More than twenty years ago, the European Muon Collaboration published their first experimental results on the proton spin structure as revealed in polarized deep inelastic lepton-nucleon scattering, and concluded that quarks contribute very little to the proton's spin. With additional experimental and theoretical investigations and progress in the following years, it is now established that, contrary to naive quark model expectations, quarks and anti-quarks carry only about 30% of the total spin of the proton. Twenty years later, the discovery from the polarized hadron collider at RHIC was equally surprising. For the phase space probed by existing RHIC experiments, gluons do not seem to contribute any to the proton's spin. To find out what carries the remaining part of proton's spin is a key focus in current hadronic physics and also a major driving force for the new generation of spin experiments at RHIC and Jefferson Lab and at a future Electron Ion Collider. It is therefore very important and timely to organize a series of annual spin physics meetings to summarize the status of proton spin physics, to focus the effort, and to layout the future perspectives. This summer program on 'Nucleon Spin Physics' held at Brookhaven National Laboratory (BNL) on July 14-27, 2010 [http://www.bnl.gov/spnsp/] is the second one following the Berkeley Summer Program taken place in June of 2009. This program at BNL focused on theory and had many presentations on a wide range of theoretical aspects on nucleon spin, from perturbative-QCD calculations to models, and to the first principle lattice calculation. It also had a good number of summary talks from all major experimental collaborations on spin physics. The program facilitated many discussions between theorists as well as experimentalists. With five transparencies from each presentation at the Summer Program, this proceedings provides a valuable summary on the status and progress, as well as the future prospects of spin physics.
Aschenauer, A.; Qiu, Jianwei; Vogelsang, W.; Yuan, F.
Spin angular momentum transfer in current-perpendicular nanomagnetic junctions
Spin angular momentum transfer, or spin-transfer, describes the transfer of spin angular momentum between a spin-polarized current and a ferromagnetic conductor. The angular momentum transfer exerts a torque (spin-current induced torque, or spin-torque) ...
J. Z. Sun
Electron-Mediated Nuclear-Spin Interactions Between Distant NV Centers
We propose a scheme enabling controlled quantum coherent interactions between separated nitrogen-vacancy centers in diamond in the presence of strong magnetic fluctuations. The proposed scheme couples nuclear qubits employing the magnetic dipole-dipole interaction between the electron spins and, crucially, benefits from the suppression of the effect of environmental magnetic field fluctuations thanks to a strong microwave driving. This scheme provides a basic building block for a full-scale quantum information processor or quantum simulator based on solid-state technology.
A. Bermudez; F. Jelezko; M. B. Plenio; A. Retzker
Understanding and controlling complex states arising from magnetic frustration
Much of our national security relies on capabilities made possible by magnetism, in particular the ability to compute and store huge bodies of information as well as to move things and sense the world. Most of these technologies exploit ferromagnetism, i.e. the global parallel alignment of magnetic spins as seen in a bar magnet. Recent advances in computing technologies, such as spintronics and MRAM, take advantage of antiferromagnetism where the magnetic spins alternate from one to the next. In certain crystal structures, however, the spins take on even more complex arrangements. These are often created by frustration, where the interactions between spins cannot be satisfied locally or globally within the material resulting in complex and often non-coplanar spin textures. Frustration also leads to the close proximity of many different magnetic states, which can be selected by small perturbations in parameters like magnetic fields, temperature and pressure. It is this tunability that makes frustrated systems fundamentally interesting and highly desirable for applications. We move beyond frustration in insulators to itinerant systems where the interaction between mobile electrons and the non-coplanar magnetic states lead to quantum magneto-electric amplification. Here a small external field is amplified by many orders of magnitude by non-coplanar frustrated states. This greatly enhances their sensitivity and opens broader fields for applications. Our objective is to pioneer a new direction for condensed matter science at the Laboratory as well as for international community by discovering, understanding and controlling states that emerge from the coupling of itinerant charges to frustrated spin textures.
Zapf, Vivien [Los Alamos National Laboratory
High Temperature, Large Sample Volume, Constant Flow Magic Angle Spinning NMR Probe for a 11
High Temperature, Large Sample Volume, Constant Flow Magic Angle Spinning NMR Probe for a High Temperature, Large Sample Volume, Constant Flow Magic Angle Spinning NMR Probe for a 11.7 T Magnetic Field for In Situ Catalytic Reaction Characterization Project start date: April 1, 2007 EMSL Lead Investigator: Joseph Ford, EMSL High Field Magnetic Resonance Facility Co-investigators: Jian Zhi Hu, Macromolecular Structure and Dynamics, Biological Science Division, FCSD Jesse Sears and David W. Hoyt, EMSL High Field Magnetic Resonance Facility Detailed understanding of the mechanisms involved in a catalytic reaction requires identification of the nature of the active sites and the temporal evolution of reaction intermediates. Although optical methods such as UV-visible and infrared (IR) spectroscopies can be used for some types of reactions, these do not
Magnetic Storms
... magnetic reversal. As there is no predictive science of geomagnetism, we currently lack even simple forecasts. Our scientific ...
Magnetic Imaging
... data-storage and permanent magnets with increased energy products, in ... Optimization of future materials, including improved yields, requires an ...
Magnetic Properties
...Since the discovery of high-temperature superconductors in 1986 (Ref 10), the demonstration of magnetic flux exclusion
A direct measurement of rotatable and frozen CoO spins in exchange bias system of CoO/Fe/Ag(001)
The exchange bias of epitaxially grown CoO/Fe/Ag(001) was investigated using x-ray magnetic circular dichroism and x-ray magnetic linear dichroism (XMLD) techniques. A direct XMLD measurement on the CoO layer during the Fe magnetization reversal shows that the CoO compensated spins are rotatable at thinner thickness and frozen at larger thickness. By a quantitative determination of the rotatable and frozen CoO spins as a function of the CoO film thickness, we find the remarkable result that the exchange bias is well established before frozen spins are detectable in the CoO film. We further show that the rotatable and frozen CoO spins are uniformly distributed in the CoO film.
Wu, J.; Park, J. S.; Kim, W.; Arenholz, E.; Liberati, M.; Scholl, A.; Wu, Y. Z.; Hwang, C.; Qiu, Z. Q.
Nuclear spin-lattice relaxation from fractional wobbling in a cone
We consider nuclear spin-lattice relaxation rate resulted from a fractional diffusion equation for anomalous rotational wobbling in a cone. The mechanism of relaxation is assumed to be due to dipole-dipole interaction of nuclear spins and is treated within the framework of the standard Bloemberger, Purcell, Pound - Solomon scheme. We consider the general case of arbitrary orientation of the cone axis relative the magnetic field. The BPP-Solomon scheme is shown to remain valid for systems with the distribution of the cone axes depending only on the tilt relative the magnetic field but otherwise being isotropic. We consider the case of random isotropic orientation of cone axes relative the magnetic field taking place in powders. Also we consider the case of their predominant orientation along or opposite the magnetic field and that of their predominant orientation transverse to the magnetic field which may be relevant for, e.g., liquid crystals. Besides we treat in details the model case of the cone axis directed along the magnetic field. The latter provides direct comparison of the limiting case of our formulas with the textbook formulas for ordinary isotropic rotational diffusion. We show that the present model enables one to obtain naturally the well known power law for Larmor frequency dependence of the spin-lattice relaxation rate. The latter is observed in some complex systems. From this law the dependence of the fractional diffusion coefficient on the fractional index is obtained to have a rather simple functional form. The dependence of the spin-lattice relaxation rate on the cone half-width for the case of ordinary rotational diffusion yields results similar to those predicted by the model-free approach.
A. E. Sitnitsky
On the origin of high- spin states in nuclear fission fragments
In the "nucleon-phase" model of binary fission, the transfer of nucleons between an A =126 {\\guillemotleft} nucleon core {\\guillemotright} and the primordial "cluster" can explain both the formation of high- spin states and the saw-tooth behavior of the variation, as a function of fragment mass, of the average angular momentum.
G. Mouze; C. Ythier; S. Hachem
Electroproduction of {rho}{sup 0} mesons on protons in quasielastic kinematics at intermediate energies and spin-flip mechanism of direct meson knockout
It is shown that the amplitude for the direct knockout of {rho}{sup 0} mesons plays an important role at energies W above the resonance region, W {>=} 2 GeV, and rather high values of Q{sup 2} {>=} 1.5-2 GeV{sup 2}/c{sup 2} and that it corresponds to the t pole in the channel of the virtual decay p {sup {yields}}p + {pi}{sup 0} accompanied by quark-spin flip upon momentum transfer to the meson, {pi}{sup 0} + {gamma}*{sub T} {sup {yields} {rho}0}. The contributions of several scalar mesons (p {sup {yields}}p + f{sub 0} channel), the contribution of the tensor meson f{sub 2}, and effects of the interference between different contributions were taken into account in addition to the contribution of the {pi}{sup 0} meson. The vectorand tensor-meson-dominance models were used to estimate the respective vertex constants. Within the proposed mechanism, the differential cross sections d{sigma}{sub L}/dt and d{sigma}{sub T}/dt were calculated for several W and Q{sup 2} values at which the respective total cross sections were measured by the CLAS Collaboration. Agreement with data on the transverse part of the total cross section, {sigma}{sub T}, was attained, whereby the assumption of a dominant role of magnetic spin transitions in the meson skin of the nucleon under conditions of quasielastic-knockout kinematics is confirmed. At the same time, the contribution of spin-flip transitions is suppressed in the longitudinal part of the cross section, {sigma}{sub L}, and this is confirmed by the results of our calculations. The behavior of the differential cross section d{sigma}{sub T}/dt is predicted with an eye to future experiments.
Obukhovsky, I. T., E-mail: firstname.lastname@example.com; Neudatchin, V. G.; Sviridova, L. L.; Fedorov, D. K., E-mail: firstname.lastname@example.com [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation)
Organic light-emitting devices using spin-dependent processes
The maximum luminous efficiency of organic light-emitting materials is increased through spin-dependent processing. The technique is applicable to all electro-luminescent processes in which light is produced by singlet exciton decay, and all devices which use such effects, including LEDs, super-radiant devices, amplified stimulated emission devices, lasers, other optical microcavity devices, electrically pumped optical amplifiers, and phosphorescence (Ph) based light emitting devices. In preferred embodiments, the emissive material is doped with an impurity, or otherwise modified, to increase the spin-lattice relaxation rate (i.e., decrease the spin-lattice time), and hence raise the efficiency of the device. The material may be a polymer, oligomer, small molecule, single crystal, molecular crystal, or fullerene. The impurity is preferably a magnetic or paramagnetic substance. The invention is applicable to IR, UV, and other electromagnetic radiation generation and is thus not limited to the visible region of the spectrum. The methods of the invention may also be combined with other techniques used to improve device performance.
Vardeny, Z. Valy (Salt Lake City, UT); Wohlgenannt, Markus (Salt Lake City, UT)
Low energy ion beam assisted deposition of a spin valve
The spin dependent electron transport in giant magnetoresistive (GMR) multilayers is significantly affected by the atomic scale structure of their interfaces. Devices with atomically flat and chemically sharp interfaces are preferred for magnetic sensor and memory applications. Recent atomic simulations of the atom-by-atom assembly of these devices indicate that near optimal interfacial structures can be created using low energy, ion assisted vapor deposition techniques with ion energies in the 5-10 eV range. A recently developed biased target ion beam deposition system has been used to experimentally test this hypothesis. Prototypical Ta/NiFe/Co/Cu/Co/FeMn/Cu spin valve structures were first grown using (simultaneous) argon ion assistance during deposition of the Co/Cu/Co trilayer part of the spin valve multilayer. Assisting ion energies of around 10 eV resulted in structures with a 30% higher magnetoresistance ratio and significantly reduced coupling field compared to samples grown with no ion assistance or with ion energies above 15 eV. These results are consistent with the atomistic simulation predictions. Other promising ion assistance schemes identified by the simulations were then used to deposit the Ta, NiFe, FeMn, and the top copper layer. A near optimal strategy was identified that resulted in the further improvement of the GMR ratio.
Quan, J. J.; Wolf, S. A.; Wadley, H. N. G. [Department of Materials Science and Engineering, School of Engineering and Applied Science, University of Virginia, Charlottesville, Virginia 22903 (United States)
Magnetic hose: Routing and Long-distance Transportation of Magnetic Fields
Magnetism is a fundamental interaction shaping our physical world, at the basis of technologies such as magnetic recording or energy generation. Unlike electromagnetic waves, which can be routed and transmitted with waveguides to long distances, magnetic fields rapidly decay with distance. Here we show the concept, design, and properties of a magnetic hose which enables to transfer the static magnetic field generated by a source to an arbitrary distance, and along any given trajectory. Using transformation optics, adapted to static magnetic fields, we first introduce an ideal scheme displaying the basic mechanism behind our proposal and allowing for a perfect transfer. Then we present a simplified approach, which allows to construct a magnetic hose using two available materials: a superconducting shell with a ferromagnetic core. Such a magnetic hose can guide and transport magnetic fields to large distances, unlike ferromagnets- the conventional existing method-, for which transmitted fields decay quickly with the ferromagnetic length. As a proof of pinciple experiment, we demonstrate the field transmission through superconducting-ferromagnetic hoses with lengths up to 140mm, which improve the transmission of an analogous ferromagnet by a 400% factor. Magnetic hoses may provide new solutions in enhancing spin couplings in all-magnetic logic schemes and in harnessing quantum systems by addressable magnetic fields, in the context of quantum information processing.
Carles Navau; Jordi Prat-Camps; Oriol Romero-Isart; J. Ignacio Cirac; Alvaro Sanchez
Argonne CNM: Electronic and Magnetic Materials and Devices Research
Electronic & Magnetic Materials & Devices Electronic & Magnetic Materials & Devices Group Leader: Saw-Wai Hla The objective of the Electronic and Magnetic Materials and Devices (EMMD) group at the CNM is to discover, understand, and utilize new electron and spin-based materials and phenomena in constrained geometries. Potential benefits include reduced power dissipation, new medical imaging methods and therapies, improved efficiency of data storage by spin current and electrical field-assisted writing, and enhanced energy conversion in photovoltaic devices. Research Activities Understanding complex magnetic order and coupling phenomena: Magnetic nanostructures are prone to complex magnetic ordering phenomena that do not occur in the bulk and that will have strong impact on the further development of functional magnetic nanostructures. Basic science on the influence of demagnetizing effects, geometrical frustration, next-nearest neighbor exchange interactions, unusual anisotropy values, and the spin-orbit interaction at reduced dimensionality are performed with a special focus on temperature-dependent magnetic order-disorder transitions.
PHYSICAL REVIEW A VOLUME 41, NUMBER 3 1 FEBRUARY 1990 Optically driven spin nutations in the ground state of atomic sodium
PHYSICAL REVIEW A VOLUME 41, NUMBER 3 1 FEBRUARY 1990 Optically driven spin nutations in the ground superposition of the magnetic substates which evolves un- der the combined influence of the magnetic and optical situation is analyzed where two states are sublevels of an electronic ground state. On the other hand, we
Suter, Dieter
Generalized correlation functions for conductance fluctuations and the mesoscopic spin Hall effect
We study the spin-Hall conductance fluctuations in ballistic mesoscopic systems. We obtain universal expressions for the spin and charge current fluctuations, cast in terms of current-current autocorrelation functions. We show that the latter are conveniently parametrized as deformed Lorentzian shape lines, functions of an external applied magnetic field and the Fermi energy. We find that the charge current fluctuations show quite unique statistical features at the symplectic-unitary crossover regime. Our findings are based on an evaluation of the generalized transmission coefficients correlation functions within the stub model and are amenable to experimental test.
J. G. G. S. Ramos; A. L. R. Barbosa; D. Bazeia; M. S. Hussein; C. H. Lewenkopf
Spin ice in a field: Quasi-phases and pseudo-transitions
Thermodynamics of a short-range model of spin ice magnets in a field is considered in the Bethe-Peierls approximation. The results obtained for [111], [100], and [011] fields agree reasonably well with the existing Monte Carlo simulations and some experiments. In this approximation, all extremely sharp field-induced anomalies are described by analytic functions of temperature and the applied field. In spite of the absence of true phase transitions, the analysis of the entropy and specific heat reliefs over the H-T plane allows discerning 'pseudo-phases' with a specific character of spin fluctuations and defining the lines of relatively sharp 'pseudo-transitions' between them.
Timonin, P. N., E-mail: firstname.lastname@example.com [Southern Federal University (Russian Federation)
Glass-wool study of laser-induced spin currents en route to hyperpolarized Cs salt
The nuclear spin polarization of optically pumped Cs atoms flows to the surface of Cs hydride in a vapor cell. A fine glass wool lightly coated with the salt helps greatly increase the surface area in contact with the pumped atoms and enhance the spin polarization of the salt nuclei. Even though the glass wool randomly scatters the pump light, the atomic vapor can be polarized with unpolarized light in a magnetic field. The measured enhancement in the salt enables study of the polarizations of light and atomic nuclei very near the salt surface.
Ishikawa, Kiyoshi [Graduate School of Material Science, University of Hyogo, Ako-gun, Hyogo 678-1297 (Japan)
The Demand Response Spinning Reserve project is a pioneeringdemonstration of how existing utility load-management assets can providean important electricity system reliability resource known as spinningreserve. Using aggregated demand-side resources to provide spinningreserve will give grid operators at the California Independent SystemOperator (CAISO) and Southern California Edison (SCE) a powerful, newtool to improve system reliability, prevent rolling blackouts, and lowersystem operating costs.
Eto, Joseph H.; Nelson-Hoffman, Janine; Torres, Carlos; Hirth,Scott; Yinger, Bob; Kueck, John; Kirby, Brendan; Bernier, Clark; Wright,Roger; Barat, A.; Watson, David S.
The Transmission Property of the Discrete Heisenberg Ferromagnetic Spin Chain
We present a mechanism for displaying the transmission property of the discrete Heisenberg ferromagnetic spin chain (DHF) via a geometric approach. By the aid of a discrete nonlinear Schr\\"odinger-like equation which is the discrete gauge equivalent to the DHF, we show that the determination of transmitting coefficients in the transmission problem is always bistable. Thus a definite algorithm and general stochastic algorithms are presented. A new invariant periodic phenomenon of the non-transmitting behavior for the DHF, with a large probability, is revealed by an adoption of various stochastic algorithms.
Qing Ding; Wei Lin
Spin-orbit holds the heavyweight title for Pu and Am: Exchange regains it for Cm
The conclusions of this paper are: (1) The 5f electrons in Cm are near an LS coupling scheme. (2) This coupling scheme allows for a large spin polarization of the 5f electrons, which in turn stabilizes the Cm III crystal structure. (3) Results for Cm show us the recipe for magnetic stabilization of the crystal structure of metals: (A) The metal must be near the itinerant-localized transition where multiple crystal structures have close energies; (B) The metal is just on the magnetic side of the transition; and (C) There must be a magnetic moment large enough to overcome the energy difference between crystal structures, thus dictating the atomic geometry. (4) These results solidify our understanding of magnetically-stabilized metals, showing us where to look for engineered materials with magnetic applications.
Moore, K; der Laan, G v; Soderlind, P
Cooperative spin decoherence and population transfer
An ensemble of multilevel atoms is a good candidate for a quantum information storage device. The information is encrypted in the collective ground state atomic coherence, which, in the absence of external excitation, is decoupled from the vacuum and therefore decoherence free. However, in the process of manipulation of atoms with light pulses (writing, reading), one inadvertently introduces a coupling to the environment, i.e. a source of decoherence. The dissipation process is often treated as an independent process for each atom in the ensemble, an approach which fails at large atomic optical depths where cooperative effects must be taken into account. In this paper, the cooperative behavior of spin decoherence and population transfer for a system of two, driven multilevel-atoms is studied. Not surprisingly, an enhancement in the decoherence rate is found, when the atoms are separated by a distance that is small compared to an optical wavelength; however, it is found that this rate increases even further for somewhat larger separations for atoms aligned along the direction of the driving field's propagation vector. A treatment of the cooperative modification of optical pumping rates and an effect of polarization swapping between atoms is also discussed, lending additional insight into the origin of the collective decay.
C. Genes; P. R. Berman
Definition: Spinning Reserve | Open Energy Information
Open Energy Info (EERE)
Spinning Reserve Spinning Reserve Jump to: navigation, search Dictionary.png Spinning Reserve Unloaded generation that is synchronized and ready to serve additional demand.[1] View on Wikipedia Wikipedia Definition In electricity networks, the operating reserve is the generating capacity available to the system operator within a short interval of time to meet demand in case a generator goes down or there is another disruption to the supply. Most power systems are designed so that, under normal conditions, the operating reserve is always at least the capacity of the largest generator plus a fraction of the peak load. The operating reserve is made up of the spinning reserve as well as the non-spinning or supplemental reserve: The spinning reserve is the extra generating capacity
Magnetic Materials
Oct 27, 2009 ... Extreme magnetic fields (>2 tesla), especially when combined with temperature, are being shown to revolutionize materials processing and�...
Spin-Resolved Electronic Structure of Ultrathin Epitaxial Fe Films on Vicinal and Singular GaAs(100) Substrates
Recently there has been considerable interest in the study of spin injection at ferromagnetic semiconductor heterojunctions and ferromagnetic metal--semiconductor contacts. Studies of ntype semiconductors have demonstrated spin-coherent transport over large distances5 and the persistence of spin coherence over a sizeable time scale. Clearly such investigations have been stimulated by the potential of the development of ''spintronics'', electronic devices utilizing the information of the electron spin states. To understand and improve the magnetic properties of ultrathin Fe films on GaAs has been the aim of many research groups over recent years. The interest in this system has both technological and fundamental scientific motivations. Technologically, Fe on GaAs may serve to realize spin electronic devices. From a fundamental science point of view, Fe on GaAs serves as a prototype for studies of the interplay between the crystalline structure and morphology of an ultrathin film, its electronic structure and the long range magnetic order it exhibits. Furthermore, it is well known that an oxidized Cs layer on GaAs substantially alters the work-function of the GaAs surface, which plays a very important role in the application of GaAs as a spin polarized electron source.
Morton, S A; Waddill, G D; Spangenberg, M; Seddon, E A; Neal, J; Shen, T; Tobin, J G
Quantifying the importance of orbital over spin correlations in delta-Pu within density-functional theory
Spin and orbital and electron correlations are known to be important when treating the high-temperature {delta} phase of plutonium within the framework of density-functional theory (DFT). One of the more successful attempts to model {delta}-Pu within this approach has included condensed-matter generalizations of Hund's three rules for atoms, i.e., spin polarization, orbital polarization, and spin-orbit coupling. Here they perform a quantitative analysis of these interactions relative rank for the bonding and electronic structure in {delta}-Pu within the DFT model. The result is somewhat surprising in that spin-orbit coupling and orbital polarization are far more important than spin polarization for a realistic description of {delta}-Pu. They show that these orbital correlations on their own, without any formation of magnetic spin moments, can account for the low atomic density of the {delta} phase with a reasonable equation-of-state. In addition, this unambiguously non-magnetic (NM) treatment produces a one-electron spectra with resonances close to the Fermi level consistent with experimental valence band photoemission spectra.
Soderlind, P; Wolfer, W
Adaptive nonparametric regression on spin fiber bundles
The construction of adaptive nonparametric procedures by means of wavelet thresholding techniques is now a classical topic in modern mathematical statistics. In this paper, we extend this framework to the analysis of nonparametric regression on sections ... Keywords: 42B35, 42C10, 42C40, 46E35, 62G08, 62G20, Adaptive nonparametric regression, Mixed spin needlets, Spin Besov spaces, Spin fiber bundles, Thresholding
Claudio Durastanti; Daryl Geller; Domenico Marinucci
Higher Spin Black Holes from CFT
Higher spin gravity in three dimensions has explicit black holes solutions, carrying higher spin charge. We compute the free energy of a charged black hole from the holographic dual, a 2d CFT with extended conformal symmetry, and find exact agreement with the bulk thermodynamics. In the CFT, higher spin corrections to the free energy can be calculated at high temperature from correlation functions of W-algebra currents.
Gaberdiel, Matthias R; Jin, Kewang
Matthias R. Gaberdiel; Thomas Hartman; Kewang Jin
Spin Chaos Manifestation in a Driven Quantum Billiard with Spin-Orbit Coupling
The coupling of orbital and spin degrees of freedom is the source of many interesting phenomena. Here, we study the electron dynamics in a quantum billiard --a mesoscopic rectangular quantum dot-- with spin-orbit coupling driven by a periodic electric field. We find that both the spatial and temporal profiles of the observables demonstrate the transition to chaotic dynamics with qualitative modifications of the power spectra and patterns of probability and spin density. The time dependence of the wavefunctions and spin density distributions indicates spin-charge separation {seen in the decay of the spin-charge density correlators}. This new spin chaos effect can be experimentally verified leading to a better understanding of the interplay between spin and spatial degrees of freedom, relevant to fundamental and applied quantum physics.
D. V. Khomitsky; A. I. Malyshev; E. Ya. Sherman; M. Di Ventra
Spin current switching and spin-filtering effects in Mn-doped boron nitride nanoribbons
The spin transport properties are investigated by means of the first principle approach for boron nitride nanoribbons with one or two substitutional Mn impurities, connected to graphene electrodes. The spin current polarization is evaluated using the ...
G. A. Nemnes
Quantized magnetic flux through the orbits of hydrogen-like atoms within the atomic model of Sommerfeld
Within the Sommerfeld atomic model the quantization of magnetic flux through the electronic orbits is investigated together with its dependency on additional sources of magnetic fields. These sources alter the magnetic flux through the atomic orbits and in consequence are causing energy shifts. This effect is investigated for the cases, where the source is an external magnetic field, the magnetic moment of the nucleus or the magnetic moment of the electron. The energy shifts due to external magnetic fields, the magnetic dipole contribution of the hyperfine splitting and the spin-orbit coupling can be reproduced very well. The meaning of 'spin', however, changes within this approach drastically. The unusual Land\\'e g-factor of 2 for the electron is a result of the orbital motion and the magnetic moment of the electron rather than it is an intrinsic property of the electron.
W. -D. R. Stein
Effect of Secondary Echo Signals in Spin-Systems with a Large Inhomogeneous Broadening of NMR Line
The possibility of comparatively simple and fast determination of characteristic relaxation parameters T1, T2 and T3 for nuclear spin-systems with strong Larmor and Rabi inhomogeneous broadenings of NMR lines using the secondary echo signal effect was experimentally shown. Resides, this method gives opportunity to obtain a valuable infomation on the inhomogeneous NMR broadening which reflects the character of magnetic field microscopic destribution in such systems, as example, multidomain magnetics and superconductors.
J. G. Chigvinadze; G. I. Mamniashvili; Yu. G. Sharimanov
The angular momentum of a magnetically trapped atomic condensate
For an atomic condensate in an axially symmetric magnetic trap, the sum of the axial components of the orbital angular momentum and the hyperfine spin is conserved. Inside an Ioffe-Pritchard trap (IPT) whose magnetic field (B-field) is not axially symmetric, the difference of the two becomes surprisingly conserved. In this paper we investigate the relationship between the values of the sum/difference angular momentums for an atomic condensate inside a magnetic trap and the associated gauge potential induced by the adiabatic approximation. Our result provides significant new insight into the vorticity of magnetically trapped atomic quantum gases.
P. Zhang; H. H. Jen; C. P. Sun; L. You
Spin Physics Program at RHIC-PHENIX
Longitudinal spin physics program at RHIC-PHENIX is introduced. Recent results of pi0 cross section and A_LL are presented and discussed.
K. Aoki; for the PHENIX Collaboration
M. Mehring, "High Resolution NMR Spectroscopy", Springeret al. , Multiple Quantum NMR, International Summer SchoolLBL-6984 ('. / Preprint NMR OOUBLE QUANTUM SPIN DECOUPLING
Pines, A.
Spin-string interaction in QCD strings
I consider the question of the interaction between a QCD string and the spin of a quark or an antiquark on whose worldline the string terminates. The problem is analyzed from the point of view of a string representation for the expectation value of a Wilson loop for a spin-half particle. A string representation of the super Wilson loop is obtained starting from an effective string representation of a Wilson Loop. The action obtained in this manner is invariant under a worldline supersymmetry and has a boundary term which contains the spin-string interaction. For rectangular loops the spin-string interaction vanishes and there is no spin-spin term in the resulting heavy quark potential. On the other hand if an allowance is made for the finite intrinsic thickness of the flux tube by assuming that the spin-string interaction takes place not just at the boundary of the string world sheet but extends to a distance of the order of the intrinsic thickness of the flux tube then we do obtain a spin-spin interaction which falls as the fifth power of the distance. Such a term was previously suggested by Kogut and Parisi in the context of a flux-tube model of confinement.
Vyas, Vikram [Physics Department St. Stephen's College, Delhi University, Delhi (India)
A technique for measurement of vector and tensor polarization in solid spin one polarized targets
Vector and tensor polarizations are explicitly defined and used to characterize the polarization states of spin one polarized targets, and a technique for extracting these polarizations from nuclear magnetic resonance (NMR) data is developed. This technique is independent of assumptions about spin temperature, but assumes the target's crystal structure induces a quadrupole interaction with the spin one particles. Analysis of the NMR signals involves a computer curve fitting algorithm implemented with a fast Fourier transform method which speeds and simplifies curve fitting algorithms used previously. For accurate curve fitting, the NMR electronic circuit must be modeled by the fitting algorithm. Details of a circuit, its model, and data collected from this circuit are given for a solid deuterated ammonia target. 37 refs., 19 figs., 3 tabs.
Kielhorn, W.F.
Skyrme-Random-Phase-Approximation description of spin-flip and orbital giant resonances
The self-consistent separable random-phase approximation (SRPA) model with Skyrme forces is extended to the case of magnetic excitations and applied to the description of spin-flip and orbital M1 giant resonances in the isotopic chain $^{142-152}$Nd. The Skyrme forces SkT6, SkM*, SLy6 and SkI3 are used. The calculations show the onset of the scissors mode with increasing deformation. A specific three-peak structure of the spin-flip response is found and explained by particular neutron and proton spin-flip transitions. Although the employed forces provide an acceptable qualitative description, the Skyrme functional still needs further improvement to reproduce quantitatively the experimental data.
V. O. Nesterenko; J. Kvasil; P. Vesely; W. Kleinig; P. -G. Reinhard
Transverse electron transport in layered metallic systems: Giant magnetoresistance and injection of spins
The distribution functions for electrons differing in the sign of the spin projection and belonging to different layers (ferromagnetic and nonmagnetic) are determined from the system of Boltzmann kinetic equations. These functions make it possible to derive integral equations for electrochemical potentials for arbitrary ratios of characteristic lengths (layer thicknesses and momentum-and diffusion mean free paths) and to describe transverse electron transport both in the bulk and in the surface regions of the multilayer structure. The expressions for the effective contact resistance are derived and the value of the transverse ohmic resistance of the structure is found, as well as its spin-dependent part determined by the values of injection factors {gamma}. The values of nonequilibrium spin polarizations, which are also connected with coefficients {gamma}, are determined. The values of {gamma} are calculated for various relations between the characteristic parameters of the given system and for various types of magnetic order.
Kravchenko, V. Ya. [Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation)], E-mail: email@example.com
Creating intense polarized electron beam via laser stripping and spin-orbit interaction
The recent advance in laser field make it possible to excite and strip electrons with definite spin from hydrogen atoms. The sources of hydrogen atoms with orders of magnitude higher currents (than that of the conventional polarized electron cathods) can be obtained from H{sup -} sources with good monochromatization. With one electron of H{sup -} stripped by a laser, the remained electron is excited to upper state (2P{sup 3/2} and 2P{sup 1/2}) by a circular polarization laser light from FEL. Then, it is excited to a high quantum number (n=7) with mostly one spin direction due to energy level split of the states with a definite direction of spin and angular momentum in an applied magnetic field and then it is stripped by a strong electric field of an RF cavity. This paper presents combination of lasers and fields to get high polarization and high current electron source.
Danilov, V.; Ptitsyn, V.; Gorlov, T.
Spinning Reserve from Responsive Load
As power system costs rise and capacity is strained demand response can provide a significant system reliability benefit at a potentially attractive cost. The 162 room Music Road Hotel in Pigeon Forge Tennessee agreed to host a spinning reserve test. The Tennessee Valley Authority (TVA) supplied real-time metering and monitoring expertise to record total hotel load during both normal operations and testing. Preliminary testing showed that hotel load can be curtailed by 22% to 37% depending on the outdoor temperature and the time of day. The load drop was very rapid, essentially as fast as the 2 second metering could detect.
Kueck, John D [ORNL; Kirby, Brendan J [ORNL; Laughner, T [Tennessee Valley Authority (TVA); Morris, K [Tennessee Valley Authority (TVA)
Investigation of Molecular Magnetic Compounds Incorporating 4d and 5d Transition Metal Cyanometallates
The field of molecular magnetism has expanded rapidly since the discovery of single molecule magnets (SMMs) in the 1990�s and has witnessed extraordinary advances in the last several decades. One of the current trends in molecular magnetic research is to incorporate metal ions that have pronounced single-ion anisotropy in an effort to improve magnetic exchange interactions. The 4d and 5d transition metal ions have large spin-orbit coupling parameters which contribute to the orbital angular momentum effects that lead to anisotropic behavior. The work herein describes efforts to synthesize and characterize new cyanide-bridged molecular materials incorporating 4d and 5d transition metal ions, specifically the [Os(CN)_(6)]^(3-), [Mo(CN)_(6)]^(3-) and [W(CN)_(8)]^(3-) ions. The 5d hexacyanometallate [Os(CN)_(6)]^(3-) was incorporated into a trinuclear cyanide bridged molecule and the [Fe(CN)_(6)]^(3-) analog was prepared as a reference compound for assessing the effect of the 5d versus 3d metal ion on the magnetic properties. Both molecules exhibit SMM bistability with a pronounced increase (~90 %) in the blocking temperature (TB) of the OsIII analogue. In addition to typical SMM behavior, both compounds exhibit exchange-biased SMM behavior, a shift in the quantum tunneling of the magnetization (QTM) from zero field. This exchange-bias can be turned �on� or �off� depending on the presence of interstitial methanol molecules. New trigonal bipyramidal (TBP) molecules incorporating the rarely studies hexacyanomolybdate(III) ion are presented in chapter III of this dissertation. The molecules of general formula [M(tmphen)_(2)]_(3)[Mo(CN)_(6)]_(2) (M = V^(II), Mn^(II) and Fe^(II); tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline), represent additions to a large homologous family of TBP molecules reported by the Dunbar group over the years. The [Mo(CN)_(6)]^(3-) ion was prepared in situ by loss of one cyanide ligand from [Mo(CN)_(7)]^(4-). Of particular interest among the compounds reported is the V_(3)Mo_(2) analog which exhibits extraordinarily strong antiferromagnetic coupling (estimated J = -134 cm^(-1). The observed exchange coupling parameter is more than twice the current record for the antiferromagnetic coupling parameter for a cyanide-bridged magnetic molecule. Another set of results were obtained using the octacyanometallate anion [WV(CN)_(8)]^(3-) as a building block for the synthesis and magnetic studies of a family of new cyanide-bridged magnetic materials. The compounds exhibit several different structural motifs including three 0-D molecular compounds (two pentanuclear molecules and a linear trinuclear molecule) and a 1-D chain, findings that illustrate the structural versatility of the octacyanotungstate(V) ions. The TBP molecule, [Mn(tmphen)_(2)]_(3)[W(CN)_(8)]_(2), exhibits evidence for an out-of-phase signal when subjected to ac measurements in zero applied field. The 1-D chain also reveals evidence for the beginning of an out-of-phase signal under zero applied field which hints at single chain magnet behavior.
Southerland, Heather Irene
Spin waves in ultracold gases with exchange and spin-orbit interactions
The dynamics of spin waves in ultracold gases is investigated with allowance for exchange and spin-orbit interaction. The exact basis of atomic states is used taking into account all rotational quantum numbers of the atom. The dispersion relation for spin waves is obtained for fermions and bosons in the hydro-dynamic approximation.
Andreeva, T. L.; Rubin, P. L., E-mail: email@example.com [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)
Simulation of a Heisenberg XY- chain and realization of a perfect state transfer algorithm using liquid nuclear magnetic resonance
The three- spin chain with Heisenberg XY- interaction is simulated in a three- qubit nuclear magnetic resonance (NMR) quantum computer. The evolution caused by the XY- interaction is decomposed into a series of single- spin rotations and the $J$- coupling evolutions between the neighboring spins. The perfect state transfer (PST) algorithm proposed by M. Christandl et al [Phys. Rev. Lett, 92, 187902(2004)] is realized in the XY- chain.
Jingfu Zhang; Gui Lu Long; Wei Zhang; Zhiwei Deng; Wenzhang Liu; Zhiheng Lu
Heteronuclear dipolar couplings, total spin coherence, and bilinear rotations in NMR spectroscopy
In Chapter 1 a variety of different introductory topics are presented. The potential complexity of the nuclear magnetic resonsnace (NMR) spectra of molecules dissolved in liquid crystal solvents serves to motivate the development of multiple quantum (MQ) spectroscopy. The basics of MQ NMR are reviewed in Chapter 2. An experimental search procedure for the optimization of MQ pulse sequences is introduced. Chapter 3 discusses the application of MQ NMR techniques to the measurement of dipolar couplings in heteronuclear spin systems. The advantages of MQ methods in such systems are developed and experimental results for partially oriented (1-/sup 13/C) benzene are presented. Several pulse sequences are introduced which employ a two-step excitation of heteronuclear MQ coherence. A new multiple pulse method, involving the simultaneous irradiation of both rare and abundant spin species, is described. The problem of the broadening of MQ transitions due to magnetic field inhomogeneity is considered in Chapter 4. The method of total spin coherence transfer echo spectroscopy (TSCTES) is presented, with experimets on partially oriented acetaldehyde serving to demonstrate this new technique. TSCTES results in MQ spectra which are sensitive to all chemical shifts and spin-spin couplings and which are free of inhomogeneous broadening. In Chapter 5 the spectroscopy of spin systems of several protons and a /sup 13/C nucleus in the isotropic phase is discussed. The usefulness of the heteronuclear bilinear rotation as a calculational tool is illustrated. Compensated bilinear ..pi.. rotations, which are relatively insensitive to timing parameter missets, are presented. A new technique for homonuclear proton decoupling, Bilinear Rotation Decoupling, is described and its success in weakly coupled systems is demonstrated.
Garbow, J.R.
Dinosaur behavior
Dinosaur behavior Dinosaur behavior Name: kevv Status: N/A Age: N/A Location: N/A Country: N/A Date: Around 1993 Question: Did the movie Jurassic Park accurately reflect the known behavior of dinosaurs? Replies: Well, since we do not have an accurate record of that time period (Man showed up about ten million years after T-rex thundered across the plains of Antarctica *grin*) so we cannot say for certain WHAT the dinosaurs did. However, since they were wild animals, we can extrapolate from their modern contemporaries and from our knowledge of their individual anatomies what kind of behaviors they exhibited. A predator with large claws probably hunts by slashing and by piercing and holding on to prey. An herbivore with large spikes growing on its tail probably used them to fend off attackers like a spiked club -- I do not think it was much of a fashion statement
HDice, Highly-Polarized Low-Background Frozen-Spin HD Targets for CLAS experiments at Jefferson Lab
Large, portable frozen-spin HD (Deuterium-Hydride) targets have been developed for studying nucleon spin properties with low backgrounds. Protons and Deuterons in HD are polarized at low temperatures (~10mK) inside a vertical dilution refrigerator (Oxford Kelvinox-1000) containing a high magnetic field (up to 17T). The targets reach a frozen-spin state within a few months, after which they can be cold transferred to an In-Beam Cryostat (IBC). The IBC, a thin-walled dilution refrigerator operating either horizontally or vertically, is use with quasi-4? detector systems in open geometries with minimal energy loss for exiting reaction products in nucleon structure experiments. The first application of this advanced target system has been used for Spin Sum Rule experiments at the LEGS facility in Brookhaven National Laboratory. An improved target production and handling system has been developed at Jefferson Lab for experiments with the CEBAF Large Acceptance Spectrometer, CLAS.
Wei, Xiangdong [JLAB; Bass, Christopher [JLAB; D'Angelo, Annalisa [INFN-Roma Tor Vegata; Deur, Alexandre P. [JLAB; Dezern, Gary L. [JLAB; Ho, Dao Hoang [Carnegie Mellon U.; Kageya, Tsuneo [JLAB; Khandaker, Mahbubul A, [Idaho State U.; Kashy, David H. [JLAB; Laine, Vivien Eric [Universite de Clermont Ferrand; Lowry, Michael M. [JLAB; O'Connell, Thomas Robert [University of Connecticut; Sandorfi, Andrew M. [JLAB; Teachey, II, Robert W. [JLAB; Whisnant, Charles Steven [James Madison U.; Zarecky, Michael R. [JLAB
Magnetic nanotubes
A magnetic nanotube includes bacterial magnetic nanocrystals contacted onto a nanotube which absorbs the nanocrystals. The nanocrystals are contacted on at least one surface of the nanotube. A method of fabricating a magnetic nanotube includes synthesizing the bacterial magnetic nanocrystals, which have an outer layer of proteins. A nanotube provided is capable of absorbing the nanocrystals and contacting the nanotube with the nanocrystals. The nanotube is preferably a peptide bolaamphiphile. A nanotube solution and a nanocrystal solution including a buffer and a concentration of nanocrystals are mixed. The concentration of nanocrystals is optimized, resulting in a nanocrystal to nanotube ratio for which bacterial magnetic nanocrystals are immobilized on at least one surface of the nanotubes. The ratio controls whether the nanocrystals bind only to the interior or to the exterior surfaces of the nanotubes. Uses include cell manipulation and separation, biological assay, enzyme recovery, and biosensors.
Matsui, Hiroshi (Glen Rock, NJ); Matsunaga, Tadashi (Tokyo, JP)
Mit Hilfe der Technologie supraleitender Magnete lassen sich in Mit Hilfe der Technologie supraleitender Magnete lassen sich in Ringbeschleunigern höhere Energien erreichen. Weil supraleitende Spulen keinen elektrischen Widerstand aufweisen, können damit stärkere Magnetfelder erzeugt werden. In normal leitenden Elektromagneten wird - wegen des elektrischen Widerstands der Drähte - die Spule aufgeheizt. Auf diese Weise geht sehr viel Energie in Form von Wärme verloren, was die Energiekosten dieser Magnete in die Höhe treibt. Supraleitende Spulen erlauben es, Magnete grosser Feldstärke unter günstigen Bedingungen zu betreiben und damit die Energiekosten zu senken. Durch den Einbau supraleitender Spulen in den Ringbeschleuniger von Fermilab konnte dessen Energie verdoppelt werden.Auch der im Bau befindliche "Large Hadron Collider" am CERN wird supraleitende Magnete
Atomic magnetic gradiometer for room temperature high sensitivity magnetic field detection
A laser-based atomic magnetometer (LBAM) apparatus measures magnetic fields, comprising: a plurality of polarization detector cells to detect magnetic fields; a laser source optically coupled to the polarization detector cells; and a signal detector that measures the laser source after being coupled to the polarization detector cells, which may be alkali cells. A single polarization cell may be used for nuclear magnetic resonance (NMR) by prepolarizing the nuclear spins of an analyte, encoding spectroscopic and/or spatial information, and detecting NMR signals from the analyte with a laser-based atomic magnetometer to form NMR spectra and/or magnetic resonance images (MRI). There is no need of a magnetic field or cryogenics in the detection step, as it is detected through the LBAM.
Xu,Shoujun (Berkeley, CA); Lowery, Thomas L. (Belmont, MA); Budker, Dmitry (El Cerrito, CA); Yashchuk, Valeriy V. (Richmond, CA); Wemmer, David E. (Berkeley, CA); Pines, Alexander (Berkeley, CA)
One fundamental requirement for quantum computation is to perform universal manipulations of quantum bits at rates much faster than the qubit's rate of decoherence. Recently, fast gate operations have been demonstrated in logical spin qubits composed of two electron spins where the rapid exchange of the two electrons permits electrically controllable rotations around one axis of the qubit. However, universal control of the qubit requires arbitrary rotations around at least two axes. Here we show that by subjecting each electron spin to a magnetic field of different magnitude we achieve full quantum control of the two-electron logical spin qubit with nanosecond operation times. Using a single device, a magnetic field gradient of several hundred milliTesla is generated and sustained using dynamic nuclear polarization of the underlying Ga and As nuclei. Universal control of the two-electron qubit is then demonstrated using quantum state tomography. The presented technique provides the basis for single and potentially multiple qubit operations with gate times that approach the threshold required for quantum error correction.
Sandra Foletti; Hendrik Bluhm; Diana Mahalu; Vladimir Umansky; Amir Yacoby
Dynamics of lipid bilayers from comparative analysis of 2 nuclear magnetic resonance relaxation data as a function
to the predominant mechanisms of nuclear spin relax- ation in lipid bilayers. To critically test various dDynamics of lipid bilayers from comparative analysis of 2 H and 13 C nuclear magnetic resonance September 1997 Analysis of the nuclear spin relaxation rates of lipid membranes provides a powerful means
Brown, Michael F.
Measurement of the neutron magnetic form factor from inclusive quasielastic scattering of polarized electrons from polarized [sup 3]He
We report a measurement of the asymmetry in spin-dependent quasielastic scattering of longitudinally polarized electrons from a polarized [sup 3]He target. The neutron magnetic form factor [ital G][sup [ital n
Gao, H.; Arrington, J.; Beise, E.J.; Bray, B.; Carr, R.W.; Filippone, B.W.; Lung, A.; McKeown, R.D.; Mueller, B.; Pitt, M.L. (California Institute of Technology, Pasadena, California 91125 (United States)); Jones, C.E. (Argonne National Laboratory, Argonne, Illinois 60439 (United States)); DeSchepper, D.; Dodson, G.; Dow, K.; Ent, R.; Farkhondeh, M.; Hansen, J.; Korsch, W.; Kramer, L.H.; Lee, K.; Makins, N.; Milner, R.G.; Tieger, D.R.; Welch, T.P. (Bates Linear Accelerator Center, Laboratory for Nuclear Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, Masschusetts 02139 (United States)); Candell, E.; Napolitano, J.; Wojtsekhowski, B.B.; Tripp, C. (Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)); Lorenzon, W. (TRIUMF, Vancouver, British Columbia, V6T 2A3 (Canada))
Abstract Using spin projection operator methods generating48. B. x~ Thus we get Spin Projection Operators Let V be ais, d It is thus a spin projection operator in the space V �
Enhancement of spin-dependent scattering and improvement of microstructure in spin valves by delayed deposition
Si/Ta/Co/Cu/CoFeMn (or NiO) spin valves were prepared by a delayed sputtering procedure, in which depositions of Ta and followed layers were intervened by 1 h. The spin valves are found to have better coherent growth with stronger (111) preferred orientations in Co and Cu layers, compared with the traditional continuous method. At the same time, the giant magnetoresistance ratio and spin-dependent scattering are enhanced by a factor of 20%-30%. These results indicate that the coherent growth and the (111) preferred orientation can enhance the spin-dependent scattering of spin valves.
Yang, D.Z.; Wang, L.; Yang, X.J.; Zhou, S.M.; Wu, X.S.; Du, J.; Hu, A.; Zhang, X.X. [Surface Physics Laboratory (State Key Laboratory) and Department of Physics, Fudan University, Shanghai 200433 (China) and Department of Physics, Southeast University, Nanjing 210096 (China); Surface Physics Laboratory (State Key Laboratory) and Department of Physics, Fudan University, Shanghai 200433 (China); National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Department of Physics, Hong Kong University of Science and Technology, Kowloon, Hong Kong (China)
Spin dynamics in (110)-oriented quantum wells
Quantum structures of III-V semiconductors grown on (110)-oriented substrates are promising for spintronic applications because they allow us to engineer and control spin dynamics of electrons. We summarise the theoretical ideas, which are the basis ... Keywords: Quantum wells, Spin dynamics, Spintronics
R. T. Harley; O. Z. Karimov; M. Henini
On the Resonant Spin Flavor Precession of the Neutrino in the Sun
This work deals with the possible solution of the solar neutrino problem in the framework of the resonant neutrino spin-flavor precession scenario. The event rate results from the solar neutrino experiments as well as the recoil electron energy spectrum from SuperKamiokande are used to constrain the free parameters of the neutrino in this model. We consider two kinds of magnetic profiles inside the sun. For both cases, a static and a twisting field are discussed.
Y. Tayalati; J. Derkaoui
Quantum Teleportation from a Propagating Photon to a Solid-State Spin Qubit
The realization of a quantum interface between a propagating photon used for transmission of quantum information, and a stationary qubit used for storage and manipulation, has long been an outstanding goal in quantum information science. A method for implementing such an interface between dissimilar qubits is quantum teleportation, which has attracted considerable interest not only as a versatile quantum-state-transfer method but also as a quantum computational primitive. Here, we experimentally demonstrate transfer of quantum information carried by a photonic qubit to a quantum dot spin qubit using quantum teleportation. In our experiment, a single photon in a superposition state of two colors -- a photonic qubit is generated using selective resonant excitation of a neutral quantum dot. We achieve an unprecedented degree of indistinguishability of single photons from different quantum dots by using local electric and magnetic field control. To teleport a photonic qubit, we generate an entangled spin-photon state in a second quantum dot located 5 meters away from the first and interfere the photons from the two dots in a Hong-Ou-Mandel set-up. A coincidence detection at the output of the interferometer heralds successful teleportation, which we verify by measuring the resulting spin state after its coherence time is prolonged by an optical spin-echo pulse sequence. The demonstration of successful inter-conversion of photonic and semiconductor spin qubits constitute a major step towards the realization of on-chip quantum networks based on semiconductor nano-structures.
Wei-bo Gao; P. Fallahi; E. Togan; A. Delteil; Y. S. Chin; J. Miguel-Sanchez; A. Imamoglu
Do Gluons Carry Proton Spin? - Toward Resolving the Spin Crisis (445th Brookhaven Lecture)
Just as Earth and other planets spin within the solar system, subatomic quark and gluon particles spin within the protons and neutrons that spin within the nucleus of an atom. Quantum Chromodynamics (QCD) is a theory that describes interactions between subatomic particles and it has played a defining role in understanding the spin of protons and neutrons, which make up most of the visible mass in the universe. Experiments first completed at CERN and furthered at several other laboratories around the world revealed that surprisingly, quarks and their partnering anti-quarks are responsible for only 20 to 30 percent of proton spin. These findings pointed to what would become known as "spin crisis." More recent experiments at BNL's Relativistic Heavy Ion Collider (RHIC), the first collider to smash protons that are "polarized," or made to spin in the same orientation, have helped to isolate the role of the gluon's spin within the spinning proton in hopes of resolving this crisis. In his lecture, Bazilevsky will explain how data from RHIC's PHENIX and STAR detectors help to reveal the role of gluons in the proton's spin. Bazilevsky will also discuss long- and short-term plans to attain a deeper look into the proton spin structure, utilizing RHIC and its future upgrades
Bazilevsky, Alexander (Physics Dept)
Surface Entanglement in Quantum Spin Networks
We study the ground-state entanglement in systems of spins forming the boundary of a quantum spin network in arbitrary geometries and dimensionality. We show that as long as they are weakly coupled to the bulk of the network, the surface spins are strongly entangled, even when distant and non directly interacting, thereby generalizing the phenomenon of long-distance entanglement occurring in quantum spin chains. Depending on the structure of the couplings between surface and bulk spins, we discuss in detail how the patterns of surface entanglement can range from multi-pair bipartite to fully multipartite. In the context of quantum information and communication, these results find immediate application to the implementation of quantum routers, that is devices able to distribute quantum correlations on demand among multiple network nodes.
S. Zippilli; S. M. Giampaolo; F. Illuminati
The importance of intra-molecular electron spin relaxation in small molecular semiconductors
Electron spin relaxation rate (eSR) is investigated on several organic semiconductors of different morphologies and molecular structures, using avoided level crossing muon spectroscopy as a local spin probe. We find that two functionalized acenes (polycrystalline tri(isopropyl)silyl-pentacene and amorphous 5,6,11,12-tetraphenyltetracene) exhibit eSRs with an Arrhenius-like temperature dependence, each with two characteristic energy scales similar to those expected from vibrations. Polycrystalline tris(8-hydroxyquinolate)gallium shows a similar behavior. The observed eSR for these molecules is no greater than 0.85 MHz at 300 K. The variety of crystal structures and transport regimes that these molecules possess, as well as the local nature of the probe, strongly suggest an intra-molecular phenomenon general to many organic semiconductors, contrasting the commonly assumed spin relaxation models based on inter-molecular charge carrier transport.
L. Schulz; M. Willis; L. Nuccio; P. Shusharov; S. Fratini; F. L. Pratt; W. P. Gillin; T. Kreouzis; M. Heeney; N. Stingelin; C. A. Stafford; D. J. Beesley; C. Bernhard; J. E. Anthony; I. Mckenzie; J. S. Lord; A. J. Drew
Nuclear Magnetic Resonance Laboratory
Nuclear Magnetic Resonance Laboratory. ... A 600 MHz Nuclear Magnetic Resonance Spectrometer. Analytical Data Compilation Reference Materials. ...
Spin Observables in Kaon Electroproduction
The CEBAF accelerator at Jefferson Lab has proven to be a powerful tool for use in studying the electromagnetic production of hadronic systems containing a strange constituent quark. The electromagnetic probe only marginally disturbs the system being investigated, and is well understood. Its use as a means to probe the internal structure of hadronic systems has been well documented. Among the most studied of these hadronic systems, currently, is the nucleon. The unique opportunities afforded by the use of polarized, high-current, high-duty-factor electron beams provides an even more powerful probe of the electromagnetic structure of hadronic systems; the study of the spin dependence of the electromagnetic production and weak decay of the hyperon, specifically the {Lambda}-hyperon, becomes feasible. An experiment to study the electroproduction of the {Lambda} as a function of virtual photon momentum transfer, angle, and energy, using spin polarization observables in order to extract insights into its production and weak decay dynamics has already been approved at Jefferson Lab (E98-101; Spin Polarization in Kaon Electroproduction). The experiment aims to study the mechanism of polarization transfer in the reaction e + p {yields} e' + K + {Lambda}. The experiment requires only moderate momentum resolution and no specialized equipment other than that associated with the polarized beam. The data quality is expected to improve with higher electron beam energies, for higher Q{sup 2} measurements. Additionally, at higher energies the increased virtual photon flux allows the 4experiment to be run at lower currents (and therefore high beam polarization). A polarized electron beam and an unpolarized cryogenic hydrogen target are required. The study uses the electron arm spectrometer and the hadron arm spectrometer to detect the scattered electron and the electroproduced kaon before it decays in flight, respectively. Additionally, the hadron arm will be used to detect the proton from the hyperon decay. The hadron arm used as a hyperon tagger, in general terms, will detect the protons resulting from the weak decays of the hyperons in {Lambda} {yields} p + {pi}.
O.K. Baker
Neutron Reflectivity and Magnetization Reversal in Heusler ...
... Giant Magnetoresistance Spintronics and Spin Valves Heusler Alloys ? Introduce Samples ... Direction SPINTRONICS AND SPIN VALVES ...
Probing a Rare Material Spin State at NIST
... work, one of the very few studies of this particular spin state, which has ... serve as a test of current and future theoretical models of exotic spin states. ...
Pushing and Understanding the Limits of Spin-Exchange ...
... This new scheme for spectral narrowing has led to increased 3He polarization for neutron spin filters polarized by spin ... Lead Organizational Unit: ...
Electron Spin Transport Demonstrated for First Time in an ...
... Project have demonstrated the first documented case of electron spin transport in ... quantum-mechanical spin of particles such as electrons and holes ...
Selective population of spin--orbit levels in the autoionization ...
Selective population of spin-orbit levels in the autoionization of a polyatomic ... individual spin-orbit components of the X 2111, ionic ground state fol ...
Tamil Nadu Spinning Mills Association TASMA | Open Energy Information
search Name Tamil Nadu Spinning Mills Association (TASMA) Place Dindigul, Tamil Nadu, India Zip 624003 Sector Wind energy Product Association of spinning mill owners; promoting...
Spin polarized current injection through HgBr{sub 2} intercalated Bi2212 intrinsic Josephson junctions.
To investigate the effect of polarized current on tunneling characteristics of intrinsic Josephson junctions (IJJs), spin-polarized and spin-degenerate current have been injected through the c-axis of HgBr{sub 2} intercalated Bi{sub 2.1}Sr{sub 1.5}Ca{sub 1.4}Cu{sub 2}O{sub 8+delta} (Bi2212) single crystals on which 10 times 10 mum{sup 2} mesas have been fabricated. These two spin conditions are achieved by depositing either Au (15 nm)/Co (80 nm)/Au (156 nm) multilayers or single Au film on HgBr{sub 2} intercalated Bi2212 with T{sub c} = 74 K followed by photolithography and Ar ion beam etching. The I-V characteristics have been measured with and without a magnetic field parallel to c-axis at 4.2 K. A fine, soft Au wire is used to make a gentle mechanical contact on the top of a particular mesa in the array. Tunneling conductance characteristics were obtained and the magnetic field dependence of sumgap voltage peaks was investigated. These peaks do not change in position with increasing magnetic field for both contact configurations. In addition, the temperature dependence of tunneling characteristics of the IJJs are obtained and existence of pseudogap feature is observed above T{sub c} for HgBr{sub 2} intercalated Bi2212.
Ozyuzer, L.; Kurter, C.; Ozdemir, M.; Zasadzinski, J. F.; Gray, K. E.; Hinks, D. G. (Materials Science Division); (Izmir Inst. of Tech.); (Illinois Inst. of Tech.)
Electron Spin Precession at CEBAF
The nuclear physics experiments at the Thomas Jefferson National Accelerator Facility often require longitudinally polarized electrons to be simultaneously delivered to three experimental halls. The degree of longitudinal polarization to each hall varies as function of the accelerator settings, making it challenging in certain situations to deliver a high degree of longitudinal polarization to all the halls simultaneously. Normally, the degree of longitudinal polarization the halls receive is optimized by changing the initial spin direction at the beginning of the machine with a Wien filter. Herein, it is shown that it is possible to further improve the degree of longitudinal polarization for multiple experimental halls by redistributing the energy gain of the CEBAF linacs while keeping the total energy gain fixed.
Douglas Higinbotham
Higinbotham, Douglas
Transverse Spin Effects at COMPASS
The investigation of transverse spin and transverse momentum effects in deep inelastic scattering is one of the key physics programs of the COMPASS collaboration. In the years 2002-2004 COMPASS took data scattering 160 GeV muons on a transversely polarized 6LiD target. In 2007, a transversely polarized NH3 target was used. Three different channels to access the transversity distribution function have been analyzed: The azimuthal distribution of single hadrons, involving the Collins fragmentation function, the azimuthal dependence of the plane containing hadron pairs, involving the two-hadron interference fragmentation function, and the measurement of the transverse polarization of lambda hyperons in the final state. Transverse quark momentum effects in a transversely polarized nucleon have been investigated by measuring the Sivers distribution function. Azimuthal asymmetries in unpolarized semi-inclusive deep-inelastic scattering give important information on the inner structure of the nucleon as well, and ca...
Schill, C
Energy Eigenvalues of Kemmer Equation for a Homogeneous Magnetic Field
This article illustrates a completely algebraic method to obtain the energy levels of a massive spin-1 particle moving in a constant magnetic field. In the process to obtain the energy levels the wave function was written by harmonic oscillator solutions.
A. Havare; K. Sogut
Suppression of nuclear spin diffusion at a GaAs/AlGaAs interface measured with a single quantum dot nano-probe
Nuclear spin polarization dynamics are measured in optically pumped individual GaAs/AlGaAs interface quantum dots by detecting the time-dependence of the Overhauser shift in photoluminescence (PL) spectra. Long nuclear polarization decay times of ~ 1 minute have been found indicating inefficient nuclear spin diffusion from the GaAs dot into the surrounding AlGaAs matrix in externally applied magnetic field. A spin diffusion coefficient two orders lower than that previously found in bulk GaAs is deduced.
A. E. Nikolaenko; E. A. Chekhovich; M. N. Makhonin; I. W. Drouzas; A. B. Vankov; J. Skiba-Szymanska; M. S. Skolnick; P. Senellart; A. Lemaitre; A. I. Tartakovskii
Learning About Magnets!
the the National High Magnetic Field Laboratory Learning About Name A magnet is a material or object that creates a magnetic fi eld. This fi eld is invisible, but it creates a force that can "attract" or "repel" other magnets and magnetic materials, like iron or nickel. What is a Magnet? This bar magnet is a permanent magnet. Permanent magnets can be found in the Earth as rocks and metals. Magnets have
Spin-resolved photoelectron spectroscopy of Fe3O4
The existence of a new class of magnetic materials displaying metallic character for one electron spin population and insulating character for the other was first populated by DeGroot et al. in 1983 based on theoretical band structure calculations of the ferromagnetic Heusler alloy NiMnSb. Since then such half metallic materials, which by definition possess 100% electron polarization at the Fermi energy, have attracted considerable theoretical, experimental, and technological interest as potential pure spin sources for use in spintronic devices. In addition to Heusler alloys (e.g. NiMnSb, PtMnSb), half metallic character has also been predicted to occur in a wide range of manganites (e.g. La1-xCaxMnO3, La1-x-SrxMnO3), metallic oxides (e.g. Fe3O4, CrO2) and CMR systems. However, such predictions have proven to be extremely difficult to confirm experimentally. Possible reasons for this include the theoretical limitations arising from the complex crystallographic structure of many such materials and limitations in applying the single electron picture to materials where strong electron correlation may be present; this is compounded by experimental difficulties posed by their structural complexity and issues such as surface contamination, segregation, and reconstruction.
Morton, Simon; Waddill, Dan; Kim, S H.; Schuller, I K.; Chambers, Scott A.; Tobin, James G.
MaxEnt-Burg Application to Muon-Spin Resonance
Muon-Spin Rotation ({mu}SR) is an experimental technique similar to Nuclear Magnetic Resonance (NMR). {mu}SR data are recorded as a set of time-series histograms of muon-decay events. Both {mu}SR and NMR regularly produce signals that are overlapping, weak and/or broadened in frequency space. These {mu}SR histograms are usually analyzed by curve fitting and Fourier transformations. However, several NMR and {mu}SR groups have developed Maximum Entropy (MaxEnt, ME) applications to improve the sensitivity of the time series analysis. We have focused on the application of the ME-Burg algorithm. The optimal number of autoregression coefficients is between N/3 and N/5 where N is the total number of data points. Selected results for simulated data and real data ME-{mu}SR applications are reported. Most of our {mu}SR work is for cuprate superconductor studies. The strength of the ME-Burg algorithm is fully used, as there is a clear relationship between the muon-spin signal S(i) at any time i and the signals S(i-k) at earlier times. ME-Burg has the major advantage of producing in the frequency transform only structure for which sufficient statistical evidence is present.
Boekema, C.; Browne, M. C. [Department of Physics and Astronomy, San Jose State University, San Jose CA 95192-0106 (United States)
Flipping Photoelectron Spins in Topological Insulators
Flipping Photoelectron Spins in Flipping Photoelectron Spins in Topological Insulators Flipping Photoelectron Spins in Topological Insulators Print Tuesday, 23 April 2013 10:00 Inherently strange crystalline materials called 3D topological insulators (TIs) are all the rage in materials science. This new phase of condensed matter is an insulator in the bulk, yet behaves like a metal on its surface, even at room temperature. The electrons that flow swiftly across the surfaces of TIs are "spin polarized", meaning the electron's spin is locked to its momentum, perpendicular to the direction of travel. These electronic states already promise many uses, but ALS researchers working at Beamline 4.0.3 with a team from Berkeley Lab and the University of California, Berkeley have just made an unexpected discovery about TIs that will broaden their possible range of applications: when hit with a photon beam, the spin polarization of the electrons they emit (in a process called photoemission) can be completely controlled in three dimensions, simply by tuning the polarization of the incident light. This strong effect was not what had been assumed about photoemission from topological insulators, or any other material. Controlling the interaction of polarized light and photoelectron spin opens a wide range of possibilities for TIs.
Low Energy Solar Neutrinos and Spin Flavour Precession
The possibility that the Gallium data effectively indicates a time modulation of the solar active neutrino flux in possible connection to solar activity is examined on the light of spin flavour precession to sterile neutrinos as a subdominant process in addition to oscillations. We distinguish two sets of Gallium data, relating them to high and low solar activity. Such modulation affects principally the low energy neutrinos ($pp$ and $^7 Be$) so that the effect, if it exists, will become most clear in the forthcoming Borexino and LENS ex