Vortex core dynamics induced by hole defects in antiferromagnetic nanodisks

TL;DR

This study uses simulations to explore vortex core behavior in antiferromagnetic nanodisks with hole defects, revealing that holes can induce oscillation or capture of the vortex core depending on their proximity.

Contribution

It is the first to demonstrate how hole defects influence vortex core dynamics in antiferromagnetic nanodisks through detailed simulations.

Findings

Holes can cause vortex core oscillation or capture.

Core dynamics depend on the distance between the core and the hole.

Vortex core can be statically trapped by a nearby hole.

Abstract

Direct observation of vortex states in an antiferromagnetic layer have been recently reported [Wu, et al, Nature Phys. 7, 303 (2011)]. In contrast to their analogues in ferromagnetic systems, namely in nanomagnets, the vortex core of antiferromagnets are not expected (and have not been observed) to present gyrotropic or any other remarkable dynamics, even when external fields are applied. Using simulated annealing and spin dynamics techniques we have been able to describe a number of properties of such a vortex state. Besides of being in agreement with reported results, our results also indicate, whenever applied to antiferromagnetic nanodisks, that the presence of holes in the sample may induce two types of motions for this vortex. Its dynamics depends upon the relative separation between its core and the hole: when they are very apart the vortex core oscillates near the nanodisk center (its equilibrium position); while, if they are sufficiently close, the core moves towards the hole where it is captured and remains static.