Skyrmion-skyrmion interaction induced by itinerant electrons in a ferromagnetic strip

TL;DR

This study numerically investigates how itinerant electrons influence skyrmion-skyrmion interactions in a ferromagnetic strip, revealing stable configurations and potential barriers that are crucial for skyrmion-based device stability.

Contribution

It introduces a detailed numerical analysis of electron-mediated skyrmion interactions in racetrack geometries, highlighting stable states and energy barriers for the first time.

Findings

Strong coupling and bound states at low electron filling.

Presence of local energy minima at specific skyrmion distances.

AFM skyrmions act as infinite potential barriers for electrons.

Abstract

Magnetic skyrmions are promising spin textures for building next-generation magnetic memories and spintronic devices. Nevertheless, one of the major challenges in realizing skyrmion-based devices is the stabilization of ordered arrays of these spin textures in different geometries. Here we numerically study the skyrmion-skyrmion interaction potential that arises due to the dynamics of itinerant electrons coupled to the magnetic texture in a ferromagnetic background with racetrack geometry. We consider different topological textures (ferromagnetic (FM) and antiferromagnetic (AFM)), namely: skyrmions, antiskyrmions and biskyrmions. We show that at low electron filling, for sufficiently short separation, the skyrmions strongly couple each other yielding a bound-state bound by electronic dynamics. However, when the filling is increased, the interaction potential energy presents local minima at specific values of the skyrmion-skyrmion distance. Each of these local minima correspond to energetically stable positions of skyrmions which are "protected" by well defined energy barriers. By inspecting the local charge density, we find that in the case of AFM skyrmions, the local antiferromagnetic nature prevents electronic penetration into the core, allowing the AFM skyrmions to be seen as infinite potential barriers for electrons.