Quasiclassical theory of the spin-orbit magnetoresistance of three-dimensional Rashba metals

TL;DR

This paper presents a theoretical study of magnetoresistance in 3D Rashba metals on ferromagnetic insulators, incorporating intrinsic and extrinsic spin-orbit effects and anisotropic spin relaxation, using a quasiclassical approach.

Contribution

It introduces a comprehensive quasiclassical model that includes various spin-orbit interactions and anisotropic relaxation to explain magnetoresistance in 3D Rashba systems.

Findings

Reproduces experimental features qualitatively

Highlights the role of anisotropic Elliott-Yafet relaxation

Shows magnetoresistance depends on spin polarization, not just spin Hall angle

Abstract

The magnetoresistance of a three-dimensional Rashba material placed on top of a ferromagnetic insulator is theoretically investigated. In addition to the intrinsic Rashba spin-orbit interaction, we also consider extrinsic spin-orbit coupling via side-jump and skew scattering, and the Elliott-Yafet spin relaxation mechanism. The latter is anisotropic due to the mass anisotropy which reflects the noncentrosymmetric crystal structure of three-dimensional Rashba metals. A quasiclassical approach is employed to derive a set of coupled spin-diffusion equations, which are supplemented by boundary conditions that account for the spin-transfer torque at the interface of the bilayer. The magnetoresistance is fully determined by the current-induced spin polarization, i.e., it cannot in general be ascribed to a single (bulk) spin Hall angle. Our theoretical results reproduce several features of the experiments, at least qualitatively, and contain established phenomenological results in the relevant limiting cases. In particular, the anisotropy of the Elliott-Yafet spin relaxation mechanism plays a major role for the interpretation of the observed magnetoresistance.