Vortex propagation and phase transitions in a chiral antiferromagnetic nanostripe

TL;DR

This paper investigates vortex dynamics in a chiral antiferromagnetic nanostripe, revealing velocity limits, phase transitions, and the stabilization of vortex chains, advancing understanding of topological excitations in magnetic nanostructures.

Contribution

It introduces the concept of hybrid chirality vortices and demonstrates the occurrence of phase transitions at high velocities in chiral antiferromagnetic nanostripes.

Findings

Vortices can reach velocities below the spin wave velocity.

Exceeding maximum vortex velocity induces phase transitions.

Vortex chains are stabilized in the stripe geometry.

Abstract

We study a vortex in a nanostripe of an antiferromagnet with easy-plane anisotropy and interfacial Dzyloshinskii-Moriya interaction. The vortex has hybrid chirality being N\'eel close to its center and Bloch away from it. Propagating vortices can acquire velocities up to a maximum value that is lower than the spin wave velocity. When the vortex is forced to exceed the maximum velocity, phase transitions occur to a nonflat spiral, vortex chain, and flat spiral, successively. The vortex chain is a topological configuration stabilised in the stripe geometry. Theoretical arguments lead to the general result that the velocity of localized excitations in chiral magnets cannot reach the spin wave velocity.