Field-driven skyrmion motion through velocity equipartition between skyrmions and a domain wall

TL;DR

This paper demonstrates that magnetic skyrmions can be moved by a uniform perpendicular magnetic field through a domain-wall mediator, revealing a velocity dependence on skyrmion number and interactions, offering new manipulation methods especially for insulating magnets.

Contribution

It introduces a novel method of skyrmion displacement using a uniform magnetic field mediated by domain walls, supported by analytical and simulation results.

Findings

Skyrmion velocity depends on the number of skyrmions as 1/(1+Ns).

Skyrmion and domain-wall interactions drive skyrmion motion.

The velocity-Ns relation is confirmed by Thiele's model.

Abstract

Magnetic skyrmions, as a whirling spin texture with axisymmetry, cannot be propelled by a uniform magnetic field. Therefore, reported skyrmion motions have been induced using other sorts of stimuli; typically, electric currents in magnetic metals as well as spin waves, thermal gradient, and field gradient have manifested their ability to drive skyrmion motion. Here, we demonstrate, through micromagnetic simulations and analytically, that magnetic skyrmions can be displaced by a uniform perpendicular magnetic field via a domain-wall (DW) mediator. For a fixed field strength, the velocity of a skyrmion train evolves in terms of 1 / (1 + Ns) with Ns denoting the number of skyrmions. Based on Thiele's model, we reproduce the velocity-Ns relation first identified from numerical results and reveal that the skyrmion-DW and inter-skyrmion repulsions offer the direct 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 magnetism and electricity, we anticipate that the scheme should also work for polar skyrmions in ferroelectrics.