![]() (c), (d) Magnons in the ferromagnet are shown producing the spin current, but different chemical potentials for up and down spins in a metallic ferromagnet would also produce a spin current if (and only if) the spin diffusion length were comparable to the sample length. When connected to a nonmagnetic metal (NM, blue), Δ T induces a spin current that is converted into a vertical electric field E ISHE and V ISHE due to the inverse spin Hall effect. These are compared to (c) the spin Seebeck effect with Δ T applied to a ferromagnet with M into the page (either metal or insulator) which produces a spin current and (d) the reciprocal spin Peltier effect. The conventional effects in (a) and (b) are dominated by thermally induced asymmetric diffusion (indicated by the large gray diffusion arrow) of both spin-up (red) and spin-down (green) electrons in (a), or voltage-induced drift (small black arrows for both spin-up and spin-down electrons) in (b), although a phonon flux is always present (as indicated schematically) as well as a magnon flux, which can contribute via momentum transfer in drag effects. (a) Conventional Seebeck effect with temperature difference Δ T applied to a metal (hot end on left), electric field E (voltage V) generated along Δ T and (b) conventional Peltier effect with applied voltage generating a temperature difference. In the absence of an additional symmetry-breaking field (as discussed in the text), m never crosses the x − y plane, i.e., these torques do not lead to magnetization reversal for uniform m. At higher current, the stationary state m is along p ^ = y ^. ![]() Below a critical current (which depends on anisotropy strength), m precesses with decreasing amplitude (dependent on damping constant α) until it reaches a stationary state with m tilted in the x − z plane where the two torques cancel, as shown in (c). As m tilts away from z ^, T sot also tilts (shown in b) along the component of p ^ perpendicular to m, and a new torque develops due to PMA, T P M A (red vector). ![]() In response to the onset of current and spin flow, m tilts in the direction of T sot i.e., toward y ^, shown in (b). This mechanism creates a spin current with spin moments pointing along p ^ ( = y ^ ) (black arrow) that flows along z ^ into the ferromagnet and travels some distance before losing spin polarization, causing spin-orbit torque T sot (blue vector) that acts on m (gold vector). (a) Charge current j flows in the x ^ direction in a strongly spin-orbit-coupled nonmagnetic metal (here Ta) (large white arrow shows electron flow along − x ^ with electrons represented as gold spheres), creating a bulk spin Hall effect. The article highlights recent discoveries of interface-induced magnetism and noncollinear spin textures, nonlinear dynamics including spin-transfer torque and magnetization reversal induced by interfaces, and interfacial effects in ultrafast magnetization processes. An overview is provided to the current state of knowledge and existing review literature on interfacial effects such as exchange bias, exchange-spring magnets, the spin Hall effect, oxide heterostructures, and topological insulators. Important concepts include spin accumulation, spin currents, spin-transfer torque, and spin pumping. It starts with an introduction and overview of how basic magnetic properties are affected by interfaces, then turns to a discussion of charge and spin transport through and near interfaces and how these can be used to control the properties of the magnetic layer. It provides a historical background and literature survey, but focuses on recent progress, identifying the most exciting new scientific results and pointing to promising future research directions. ![]() This article reviews static and dynamic interfacial effects in magnetism, focusing on interfacially driven magnetic effects and phenomena associated with spin-orbit coupling and intrinsic symmetry breaking at interfaces. ![]()
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