Walker-like domain wall breakdown in layered antiferromagnets driven by staggered spin\u2013orbit fields

Rubén M Otxoa,J Wunderlich,P E Roy,R Rama-Eiroa,J Godinho,K Y Guslienko

doi:10.1038/s42005-020-00456-5

Abstract

Within linear continuum theory, no magnetic texture can propagate faster than the maximum group velocity of the spin waves. Here, by atomistic spin dynamics simulations and supported by analytical theory, we report that a strongly non-linear transient regime due to the appearance of additional magnetic textures results in the breaking of the Lorentz translational invariance. This dynamical regime is akin to domain wall Walker-breakdown in ferromagnets and involves the nucleation of an antiferromagnetic domain wall pair. While one of the nucleated domain walls is accelerated beyond the magnonic limit, the remaining pair remains static. Under large spin–orbit fields, a cascade of multiple generation and recombination of domain walls are obtained. This result may clarify recent experiments on current pulse induced shattering of large domain structures into small fragmented domains and the subsequent slow recreation of large-scale domains.

Highlights

Within linear continuum theory, no magnetic texture can propagate faster than the maximum group velocity of the spin waves
Topological defects can be found in a variety of fields such as in superfluid helium[2] named vortices, in periodic crystal structures, they are called dislocations[3,4,5] and in magnetism, magnetic domain walls (DWs)[6,7], vortices[8,9] and skyrmions[10]
Continuum-based textures such as magnetic textures like DWs, vortices and skyrmions are often characterised by the so-called winding number whose value stands in direct relation to the magnitude of the normalised Burgers vector

Summary

Introduction

No magnetic texture can propagate faster than the maximum group velocity of the spin waves. For low values of SO-fields (see Fig. 1c), a saturation effect of the DW speed is observed, characterised by the slope of the maximum winding number density position (DW position), q, with respect to time, t with v = ∂tq.

Results

Conclusion