Magnetization and Switching Characteristics of Composite Thin Magnetic Films

Abstract

Composite magnetic thin films consisting of layers of different magnetic materials in close molecular contact with one another are studied. Because of ferromagnetic exchange coupling between spins, the magnetization in the neighborhood of the interface of the layers is expected to rotate continuously as in Bloch walls. The experimental magnetization curve of an extremely soft magnetic layer on an extremely hard magnetic layer agrees well with the theoretical curve based on such rotation models. Drastic deformations in critical switching curves from the asteroid of conventional uniaxial films, improvement in nondestructive reading characteristics, and existence of a new switching mode which is dependent upon the sequence of external magnetic fields are also expected from a theory based on a lumped-constant approximation to the continuous rotation model. All of these theoretical predictions have been confirmed by experiments using electroplated composite films.

Magnetometry and transport data complement polarized neutron reflectometry in magnetic depth profiling

“…1 The latter asymptotic field dependence can be derived from the analytic model of the exchange spring in the limit of a rigid pinning layer. 17 The successful fit serves as experimental evidence for the applicability of the rigid pinning approximation. This is in accordance with the fact that the anisotropy of the CoPt pinning layer is much larger than the anisotropy of the soft Permalloy film.…”

“…2(a)-2(c) arises when the applied field is competing with an anisotropy field giving rise to a more complex energy landscape. 17 …”

“…The discrepancy is acceptable when considering the fact that an asymptotic high field expression has been used to extract a parameter which characterizes the onset of the exchange spring behavior in the low-field sub-mT regime. We utilize the experimental value l 0 H b ¼ À0.54 mT together with the NiFe saturation moment m s ¼ 11.1 lAm 2 to calculate the exchange constant A of NiFe from the bending field expression 17 …”

The effect of CoPt crystallinity and grain texturing on properties of exchange-coupled Fe/CoPt systems

“…There have been some theoretical and empirical works carried out to elucidate how these factors can alter the coupling mechanism. [24][25][26][27][28] However, there has been limited work on the effect of grain texturing. 29 In this report, we investigate the effects of the hard layer crystallinity and grain texturing on the exchange coupling between hard/soft magnetic bilayers.…”

Spin structure at nanojunctions and constrictions

“…[10][11][12][13][14] From a theoretical point of view, the spin structure at granular interfaces and in constrained domain walls was first investigated in the context of polycrystalline rare-earth transition-metal intermetallics, 10 although various earlier articles, such as Refs. [15][16][17][18][19], anticipate much of the involved physics. A key feature is magnetization and energy-density tails extending well into the bulk of the grains.…”