Title: Novel Exotic Magnetic Spin-order in Co5Ge3 Nano-size Materials,
Abstract: The Cobalt-germanium (Co-Ge) is a fascinating complex alloy system that has
unique structure and exhibit range of interesting magnetic properties which
would change when reduce to nanoscale dimension. At this experimental work, the
high-aspect-ratio Co5Ge3 nanoparticle with average size of 8nm was synthesized
by gas aggregation-type cluster-deposition technology. The nanostructure
morphology of the as-made binary Co5Ge3 nanoparticles demonstrate excellent
single-crystalline hexagonal structure with mostly preferable growth along
(110) and (102) directions. In contrast the bulk possess Pauli paramagnetic
spin-order at all range of temperature, here we discover size-driven new
magnetic ordering of as-synthesized Co5Ge3 nanoparticles exhibiting
ferromagnetism at room temperature with saturation magnetization of Ms = 32.2
emu/cm3. This is first report of observing such new magnetic spin ordering in
this kind of material at nano-size which the magnetization has lower
sensitivity to thermal energy fluctuation and exhibit high Curie temperature
close to 850 K. This ferromagnetic behavior along with higher Curie temperature
at Co5Ge3 nanoparticles are attributes to low-dimension and quantum-confinement
effect which imposes strong spin coupling and provides a new set of size-driven
spin structures in Co5Ge3 nanoparticle which no such magnetic behavior being
present in the bulk of same material. This fundamental scientific study
provides important insights into the formation, structural, and the magnetic
property of sub 10nm Co5Ge3 nanostructure which shall lead to promising
practical versatile applications for magneto- germanide based nano-devices.