Theory of current-driven magnetization dynamics in inhomogeneous ferromagnets

TL;DR

This paper reviews recent theoretical advances in understanding how electric currents influence magnetization in inhomogeneous ferromagnets, focusing on spin torques, instabilities, and domain-wall motion.

Contribution

It provides a comprehensive phenomenological and microscopic framework for current-driven magnetization dynamics, emphasizing dissipative effects like Gilbert damping and adiabatic torque.

Findings

Analysis of spin torque origins

Description of current-induced ferromagnetic instability

Microscopic justification of damping and torque terms

Abstract

We give a brief account of recent developments in the theoretical understanding of the interaction between electric currents and inhomogeneous ferromagnetic order parameters. We start by discussing the physical origin of the spin torques responsible for this interaction and construct a phenomenological description. We then consider the electric current-induced ferromagnetic instability and domain-wall motion. Finally, we present a microscopic justification of the phenomenological description of current-driven magnetization dynamics, with particular emphasis on the dissipative terms, the so-called Gilbert damping $\alpha$ and the $\beta$ component of the adiabatic current-driven torque.