Rashba spin torque in an ultrathin ferromagnetic metal layer

TL;DR

This paper investigates the Rashba spin torque in ultrathin ferromagnetic metal layers with broken inversion symmetry, deriving a spin diffusion model to understand its effects on magnetization dynamics.

Contribution

It introduces a coherent spin diffusion equation for systems with both magnetism and spin-orbit coupling, analyzing the spin torque in different coupling regimes.

Findings

Derived a spin diffusion equation for Rashba systems

Analyzed spin torque behavior in strong and weak spin-orbit coupling limits

Discussed implications for magnetization dynamics

Abstract

In a two-dimensional ferromagnetic metal layer lacking inversion symmetry, the itinerant electrons mediate the interaction between the Rashba spin-orbit interaction and the ferromagnetic order parameter, leading to a Rashba spin torque exerted on the magnetization. Using Keldysh technique, in the presence of both magnetism and a spin-orbit coupling, we derive a spin diffusion equation that provides a coherent description to the diffusive spin dynamics. The characteristics of the spin torque and its implication on magnetization dynamics are discussed in the limits of large and weak spin-orbit coupling.