Skyrmion motion and partitioning of domain wall velocity driven by repulsive interactions

Abstract

Magnetic skyrmions, as a whirling spin texture with axisymmetry, cannot be propelled directly by a uniform perpendicular magnetic field. Therefore, reported skyrmion motions have been induced using other sorts of stimuli — typically, electric currents in magnetic metals. Here, we propose to drive skyrmion motion, in a uniform perpendicular field, by intrinsic repulsive interactions among an outer domain wall (DW) and magnetic skyrmions. Through micromagnetic simulations, we demonstrate that the uniform perpendicular magnetic field can indeed displace magnetic skyrmions alongside the leading DW. At a fixed field strength, the velocity of the skyrmion train evolves according to a 1 / (Ns + 1) relation with Ns denoting the number of skyrmions. Based on the Thiele equation, we elucidate, analytically, the mechanism of the driven magnetic skyrmion motion as well as the velocity equipartition phenomenon and reveal that the skyrmion–DW and inter-skyrmion repulsive interactions offer the driving force for skyrmion motion. This study underlines the role of spin textures’ interaction in skyrmion dynamics, and opens an alternative route for skyrmion manipulation especially relevant to insulating magnets. Given the correspondence between ferromagnetism and ferroelectricity, we anticipate that the scheme should also work for polar skyrmions in ferroelectrics.