Skyrmion inertia in synthetic antiferromagnets

TL;DR

This paper investigates the dynamics of magnetic skyrmions in synthetic antiferromagnets, revealing an inertia effect due to finite acceleration and a maximum velocity limit influenced by interlayer coupling.

Contribution

It introduces a formalism based on coupled Thiele equations to quantitatively describe skyrmion inertia and maximum velocity in synthetic antiferromagnets.

Findings

Transient regime with finite acceleration due to inertia

Time constant scales inversely with antiferromagnetic coupling

Maximum skyrmion velocity limited by coupling force

Abstract

We describe the dynamics of magnetic skyrmions in synthetic antiferromagnets (SAF), with a finite interlayer coupling. Due to the opposite gyrovector of the skyrmions in the two SAF layers, the coupled skyrmions reach a stationary regime with a spatial separation, in a direction orthogonal to their velocity. As a consequence, and contrary to the ferromagnetic situation, a transient regime necessarily occurs, with a finite acceleration, related to an inertia, and that limits its time response. The formalism developed here, based on two coupled Thiele equations, allows a quantitative description of this phenomenon. The time constant associated to the transient regime scales inversely with the antiferromagnetic coupling constant. We also show that the coupling force reaches a maximal value at a finite skyrmion separation. This sets a maximum velocity limit, beyond which the the coupling force cannot stabilize the bound state.