Brownian motion of magnetic domain walls and skyrmions, and their diffusion constants

TL;DR

This paper uses numerical simulations to study the diffusive behavior of magnetic domain walls and skyrmions in ultra-thin Co layers, revealing how their Brownian motion depends on damping and size, with implications for observing skyrmions.

Contribution

It provides the first detailed analysis of how damping influences the diffusive laws of walls and skyrmions, highlighting size-dependent effects on skyrmion diffusion suppression.

Findings

Diffusive behavior varies with damping parameter.

Skyrmion diffusion suppression occurs at ultra-low damping.

Size constraints affect the observability of skyrmion diffusion.

Abstract

Extended numerical simulations enable to ascertain the diffusive behavior at finite temperatures of chiral walls and skyrmions in ultra-thin model Co layers exhibiting symmetric - Heisenberg - as well as antisymmetric - Dzyaloshinskii-Moriya - exchange interactions. The Brownian motion of walls and skyrmions is shown to obey markedly different diffusion laws as a function of the damping parameter. Topology related skyrmion diffusion suppression with vanishing damping parameter, albeit already documented, is shown to be restricted to ultra-small skyrmion sizes or, equivalently, to ultra-low damping coefficients, possibly hampering observation.