Theory of in-plane current induced spin torque in metal/ferromagnet bilayers

Abstract

Using a semiclassical approach that simultaneously incorporates the spin Hall effect (SHE), spin diffusion, quantum well states, and interface spin-orbit coupling (SOC), we address the interplay of these mechanisms as the origin of the in-plane current induced spin torque observed in the normal metal/ferromagnetic metal bilayer thin films. Focusing on the bilayers with a ferromagnet much thinner than its spin diffusion length, such as Pt/Co with $\sim 10$nm thickness, our approach addresses simultaneously the two contributions to the spin torque, namely the spin-transfer torque (SHE-STT) due to SHE induced spin injection, and the spin-orbit torque (SOT) due to SOC induced spin accumulation. The SOC produces an effective magnetic field at the interface, hence it modifies the angular momentum conservation expected for the SHE-STT. The SHE induced spin voltage and the interface spin current are mutually dependent, hence are solved in a self-consistent manner. In addition, the spin transport mediated by the quantum well states may be responsible for the experimentally observed rapid variation of the spin torque with respect to the thickness of the ferromagnet.

9 pages, 4 figures

References in corpus (13)

• Dissipationless Quantum Spin Current at Room Temperature
• Spin Transfer Torques
• Theory of spin Hall magnetoresistance
• Semiclassical theories of the anomalous Hall effect
• Spin Transport at Interfaces with Spin-Orbit Coupling: Phenomenology
• Angular and temperature dependence of current induced spin-orbit effective fields in Ta/CoFeB/MgO nanowires
• Spin Transport at Interfaces with Spin-Orbit Coupling: Formalism
• Interface enhancement of Gilbert damping from first-principles
• Current-induced domain wall motion in Rashba spin-orbit system
• Observation of Spin-Orbit Effects with Spin Rotation Symmetry
• Theory of unidirectional spin Hall magnetoresistance in heavy-metal/ferromagnetic-metal bilayers
• Spin-orbit torques from interfacial spin-orbit coupling for various interfaces
• Angular dependence of spin-orbit spin transfer torques

Cited by in corpus (2)

• Spin torque and persistent currents caused by percolation of topological surface states
• Persistent currents and spin torque caused by percolated quantum spin Hall state