Current-induced magnetization dynamics in disordered itinerant ferromagnets

TL;DR

This paper develops a quantum kinetic framework to analyze current-induced magnetization dynamics in disordered itinerant ferromagnets, revealing how damping and spin-transfer torques influence domain-wall motion and stability.

Contribution

It introduces a self-consistent adiabatic local-density approximation to derive Gilbert damping and spin-transfer torques, highlighting differences from the s-d model and identifying a dynamic spin-transfer torque.

Findings

Steady current-driven domain-wall motion is insensitive to spin dephasing in weak ferromagnets.

Uniform magnetization is more stable against spin torques in itinerant ferromagnets.

A spin pumping-like dynamic spin-transfer torque governs domain-wall distortion.

Abstract

Current-driven magnetization dynamics in ferromagnetic metals are studied in a self-consistent adiabatic local-density approximation in the presence of spin-conserving and spin-dephasing impurity scattering. Based on a quantum kinetic equation, we derive Gilbert damping and spin-transfer torques entering the Landau-Lifshitz equation to linear order in frequency and wave vector. Gilbert damping and a current-driven dissipative torque scale identically and compete, with the result that a steady current-driven domain-wall motion is insensitive to spin dephasing in the limit of weak ferromagnetism. A uniform magnetization is found to be much more stable against spin torques in the itinerant than in the \textit{s}-\textit{d} model for ferromagnetism. A dynamic spin-transfer torque reminiscent of the spin pumping in multilayers is identified and shown to govern the current-induced domain-wall distortion.