Topology-Dependent Brownian Gyromotion of a Single Skyrmion

TL;DR

This study experimentally observes and models the topology-dependent Brownian gyromotion of a single skyrmion, revealing how thermal fluctuations induce gyromotion behavior influenced by topology, with implications for spintronic device stability.

Contribution

It provides the first experimental observation and theoretical formulation of topology-dependent Brownian gyromotion of skyrmions in magnetic materials.

Findings

Observation of thermal fluctuation-induced random walk of a skyrmion.

Identification of topology-dependent gyromotion behavior.

Formulation of gyromotion dynamics based on stochastic Thiele equation.

Abstract

Non-interacting particles exhibiting Brownian motion have been observed in many occasions of sciences, such as molecules suspended in liquids, optically trapped microbeads, and spin textures in magnetic materials. In particular, a detailed examination of Brownian motion of spin textures is important for designing thermally stable spintronic devices which motivates the present study. In this Letter, through using temporally and spatially resolved polar magneto-optic Kerr effect (MOKE) microscopy, we have experimentally observed the thermal fluctuation-induced random walk of a single isolated N\'eel-type magnetic skyrmion in an interfacially asymmetric Ta/CoFeB/TaOx multilayer. An intriguing topology dependent Brownian gyromotion behavior of skyrmions has been identified. The onset of Brownian gyromotion of a single skyrmion induced by the thermal effects, including a nonlinear temperature-dependent diffusion coefficient and topology-dependent gyromotion are further formulated based on the stochastic Thiele equation. The experimental and numerical demonstration of topology-dependent Brownian gyromotion of skyrmions can be useful for understanding the nonequilibrium magnetization dynamics and implementing spintronic devices.