A simple vision of current induced spin torque in domain walls

TL;DR

This paper presents a simple classical model to analyze current-induced spin torque in ferromagnetic domain walls, revealing how current distorts domain walls and affects depinning, especially in thin walls where the torque sign reverses.

Contribution

It extends previous theories to arbitrary domain wall widths and analyzes the role of non-uniform torque components in current-induced effects.

Findings

Current mainly distorts domain walls, potentially aiding depinning.

In thin domain walls, the current-induced pressure reverses sign.

The model provides insights into the behavior of spin torque across different wall widths.

Abstract

The effective spin pressure induced by an electric current on a domain wall in a ferromagnet is determined using a simple classical model, which allows us to extend previous theories to arbitrary domain wall widths. In particular, the role of spatially non-uniform components of the torques are analyzed in detail. We find that the effect of the current is mainly to distort the domain wall which should enhance de-pinning. We also find that in the limit of thin domain walls the current-induced pressure changes sign.