Staggered Dynamics in Antiferromagnets by Collective Coordinates

TL;DR

This paper introduces a simplified collective coordinate theory for antiferromagnet dynamics, capturing effects of dissipation, magnetic fields, and currents, and describing domain wall motion as a driven harmonic oscillator.

Contribution

The paper develops a new, simplified theoretical framework using collective coordinates to describe antiferromagnetic dynamics, incorporating dissipation and current-induced effects.

Findings

Currents induce collective motion via dissipative torques at low frequencies.

Domain wall dynamics resemble a driven harmonic oscillator.

The natural frequency of the domain wall is inversely proportional to its length.

Abstract

Antiferromagnets can be used to store and manipulate spin information, but the coupled dynamics of the staggered field and the magnetization are very complex. We present a theory which is conceptually much simpler and which uses collective coordinates to describe staggered field dynamics in antiferromagnetic textures. The theory includes effects from dissipation, external magnetic fields, as well as reactive and dissipative current-induced torques. We conclude that, at low frequencies and amplitudes, currents induce collective motion by means of dissipative rather than reactive torques. The dynamics of a one-dimensional domain wall, pinned at 90$^{\circ}$ at its ends, are described as a driven harmonic oscillator with a natural frequency inversely proportional to the length of the texture.