Current-driven dynamics of an isolated skyrmion in a racetrack with material defects: Influence of defect size and density

Abstract

Controlling particle diffusion is central to understanding both soft-matter systems and solid-state materials with unique electronic behaviors. In magnetic systems, the diffusion of skyrmions, a topologically protected spin texture, has recently been explored as a route toward functional spintronic devices. However, a comprehensive understanding of their current-induced, defect-enhanced diffusion in real thin-film environments remains an open challenge. Here, by means of micromagnetic simulations, we demonstrate that the diffusion of skyrmions can be modulated by adjusting the defect size. For defect sizes smaller than the skyrmion diameter, diffusion is anisotropic, with enhanced transport along the direction of the applied current and reduced motion perpendicular to it. This anisotropic diffusion changes to isotropic diffusion as the number of defects increases. Moreover, velocity autocorrelation analysis reveals that introducing defects larger than the skyrmion diameter can suppress the detrimental transverse motion of the skyrmion. Notably, this suppression is effective only at a specific number of defects, suggesting that both defect size and spatial distribution can serve as tuning parameters for skyrmion transport.