be in a single-domain magnet; but domain walls involve rotation of only a small part of the magnetization, so it is much easier to change the magnetic moment. The magnetization can also change by addition or subtraction of domains (called nucleation and denucleation). Measurement Magnetic hysteresis can be characterized in various ways. In general, the magnetic material is placed in a varying applied field, as induced by an electromagnet, and the resulting magnetic flux density ( field) is measured, generally by the inductive electromotive force introduced on a pickup coil nearby the sample. This produces the characteristic curve; because the hysteresis indicates a memory effect of the magnetic material, the shape of the curve depends on the history of changes in . Alternatively, the hysteresis can be plotted as magnetization in place of , giving an curve. These two curves are directly related since . The measurement may be closed-circuit or open-circuit, according to how the magnetic material is placed in a magnetic circuit. In open-circuit measurement techniques (such as a vibrating-sample magnetometer), the sample is suspended in free space between two poles of an electromagnet. Because of this, a demagnetizing field develops and the field internal to the magnetic material is different than the applied . The normal B-H curve can be obtained after the demagnetizing effect is corrected. In closed-circuit measurements (such as the hysteresisgraph), the flat faces of the sample are pressed directly against the poles of the electromagnet. Since the pole faces are highly permeable, this removes the demagnetizing field, and so the internal field is equal to the applied field. With hard magnetic materials (such as sintered neodymium magnets), the detailed microscopic process of magnetization reversal depends on whether the magnet is in an open-circuit or closed-circuit configuration, since the magnetic medium around the magnet influences the interactions between domains in a way that cannot be fully captured by a simple demagnetization factor. Models The most known empirical models in hysteresis are Preisach and Jiles-Atherton models. These models allow an accurate modeling of the hysteresis loop and are widely used in the industry. However, these models lose the connection with thermodynamics and the energy consistency is not ensured. A more recent model, with a more consistent thermodynamic foundation, is the vectorial incremental nonconservative consistent hysteresis (VINCH) model of Lavet et al. (2011). is inspired by the kinematic hardening laws and by the thermodynamics of irreversible