Magnetoelectric antiferromagnets as platforms for the manipulation of solitons

TL;DR

This paper explores the magnetic dynamics of magnetoelectric antiferromagnetic thin films, demonstrating control of soliton motion through film thickness and external magnetic fields, with potential applications in magnetic racetrack devices.

Contribution

It introduces a low-energy theory for antiferromagnetic thin films with boundary ferromagnetism and analyzes soliton dynamics, including domain walls and skyrmions, as massive particles influenced by film parameters.

Findings

Film thickness controls soliton motion.

External magnetic fields tune domain wall velocity.

Skyrmion dynamics depend on sample thickness modulation.

Abstract

We study the magnetic dynamics of magnetoelectric antiferromagnetic thin films, where an unconventional boundary ferromagnetism coexists with the bulk N\'{e}el phase below the N\'{e}el temperature. The spin exchange between the two order parameters yields an effective low-energy theory that is formally equivalent to that of a ferrimagnet. Dynamics of domain walls and skyrmions are analyzed within the collective variable approach, from which we conclude that they behave as massive particles moving in a viscous medium subjected to a gyrotropic force. We find that the film thickness can be used as a control parameter for the motion of these solitons. In this regard, it is shown that an external magnetic field can drive the dynamics of domain walls, whose terminal velocity is tunable with the sample thickness. Furthermore, the classification of the skyrmion dynamics is sensitive to the spatial modulation of the sample thickness, which can be easily engineered with the present (thin-film) deposition techniques. Current-driven spin transfer can trigger drifting orbits of skyrmions, which can be utilized as racetracks for these magnetic textures.