Skyrmion motion in a synthetic antiferromagnet driven by asymmetric spin wave emission

TL;DR

This paper demonstrates a novel method to manipulate skyrmions in synthetic antiferromagnets using asymmetric spin wave emission driven by global magnetic fields, revealing insights into skyrmion dynamics for future computing devices.

Contribution

It introduces a new technique for skyrmion control via asymmetric spin wave emission induced by combined magnetic fields, advancing skyrmion-based device design.

Findings

Skyrmion motion is driven by asymmetric spin wave emission.

Maximum skyrmion velocity occurs at the breathing mode frequency.

Exchange coupling strength significantly affects skyrmion dynamics.

Abstract

Skyrmions have been proposed as new information carriers in racetrack memory devices. To realise such devices, a small size; high speed of propagation; and minimal skyrmion Hall angle are required. Synthetic antiferromagnets (SAFs) present the ideal materials system to realise these aims. In this work, we use micromagnetic simulations to propose a new method for manipulating them using exclusively global magnetic fields. An out-of-plane microwave field induces oscillations in the skyrmions radius which in turn emits spin waves. When a static in-plane field is added, this breaks the symmetry of the skyrmions and causes asymmetric spin wave emission. This in turn drives motion of the skyrmions, with the fastest velocities observed at the frequency of the intrinsic out-of-phase breathing mode of the pair of skyrmions. This behaviour is investigated over a range of experimentally realistic antiferromagnetic interlayer exchange coupling strengths, and the results compared to previous works studying similar motion driven with an oscillating electric field. Through this the true effect of varying the exchange coupling strength is determined, and greater insight is gained into the mechanism of skyrmion motion. These results will help to inform the design of future novel computing architectures based on the dynamics of skyrmions in synthetic antiferromagnets.