Intrinsic spin-orbit torque in an antiferromagnet with a weakly noncollinear spin configuration

TL;DR

This paper investigates how weak noncollinearity in antiferromagnets affects spin-orbit torque, revealing that noncollinearity introduces additional Berry phase contributions that can significantly influence domain wall dynamics.

Contribution

It introduces the calculation of spin-orbit torque in weakly noncollinear antiferromagnets, highlighting the role of Berry phase effects absent in collinear configurations.

Findings

Noncollinearity modifies spin-orbit torque properties.

Berry phase contributions are generated by noncollinearity.

Effects are significant in clean antiferromagnets for domain wall motion.

Abstract

An antiferromagnet is a promising material for spin-orbit torque generation. Earlier studies of the spin-orbit torque in an antiferromagnet are limited to collinear spin configurations. We calculate the spin-orbit torque in an antiferromagnet whose spin ordering is weakly noncollinear. Such noncollinearity may be induced spontaneously during the magnetization dynamics even when the equilibrium spin configuration is perfectly collinear. It is shown that deviation from perfect collinearity can modify properties of the spin-orbit torque since noncollinearity generates extra Berry phase contributions to the spin-orbit torque, which are forbidden for collinear spin configurations. In sufficiently clean antiferromagnets, this modification can be significant. We estimate this effect to be of relevance for fast antiferromagnetic domain wall motion.