Defect-enhanced diffusion of magnetic skyrmions

Abstract

Defects, i.e., inhomogeneities of the underlying lattice, are ubiquitous in magnetic materials and can have a crucial impact on their applicability in spintronic devices. For magnetic skyrmions, localized and topologically nontrivial spin textures, they give rise to a spatially inhomogeneous energy landscape and can lead to pinning, resulting in an exponentially increased dwell time at certain positions and typically a strongly reduced mobility. Using atomistic spin dynamics simulations, we reveal that under certain conditions, defects can instead enhance thermal diffusion of ferromagnetic skyrmions. By comparing with results for the diffusion of antiferromagnetic skyrmions and using a quasiparticle description based on the Thiele equation, we demonstrate that this surprising finding can be traced back to the partial lifting of the impact of the topological gyrocoupling, which governs the dynamics of ferromagnetic skyrmions in the absence of defects.