Role of impurity clusters for the current-driven motion of magnetic Skyrmions

TL;DR

This paper investigates how different types of impurities affect the current-driven motion of magnetic Skyrmions in racetrack geometries, revealing various dynamic behaviors and phase diagrams.

Contribution

It introduces a numerical study of impurity effects on Skyrmion dynamics, distinguishing between non-conducting and magnetic impurities and analyzing their impact.

Findings

Impurities cause Skyrmion decay, pinning, or creation depending on parameters.

Inhomogeneous current density arises from non-conducting impurities, while magnetic impurities do not alter current distribution.

Phase diagrams show impurity concentration and size influence Skyrmion behavior.

Abstract

We study how impurities influence the current-induced dynamics of magnetic Skyrmions moving in a racetrack geometry. For this, we solve numerically the generalized Landau-Lifshitz-Gilbert equation extended by the current-induced spin transfer torque. In particular, we investigate two classes of impurities, non-conducting and magnetic impurities. The former are magnetically rigid objects and yield to an inhomogeneous current density over the racetrack which we determine separately by solving the fundamental electrostatic equations. In contrast, magnetic impurities leave the applied current density homogeneous throughout the stripe. Depending on parameters, we observe four different scenarios of Skyrmion motions in the presence of disorder, the Skyrmion decay, the pinning, the creation of additional Skyrmions, and ordinary Skyrmion passage. We calculate and discuss phase diagrams in dependence of the impurity concentration and radii of the impurities.