Skyrmion bound state and dynamics in an antiferromagnetic bilayer racetrack

TL;DR

This paper explores the interaction and dynamics of skyrmions in a coupled antiferromagnetic bilayer racetrack system, revealing bound states influenced by current and impurities, with implications for spintronic devices.

Contribution

It introduces a detailed analysis of skyrmion bound states and their dynamics in antiferromagnetic bilayer racetracks, including effects of current and impurities, which is novel in the field.

Findings

Skyrmions can form stable bound states depending on their separation.

Current density influences the nucleation of bound states.

Bound states are robust against magnetic impurities.

Abstract

We investigate the dynamics of two skyrmions lying in distinct layers of an antiferromagnetic bilayer system, consisting of nanostripes with the shape of racetracks. The top and bottom nanostripes are separated by a height offset and they are coupled through a ferromagnetic exchange, allowing the interaction between the skyrmions from both layers. Depending on the distance between the skyrmions they attract each other sufficiently to achieve a bound state. We also analyze their dynamics when an electric current is applied in a unique layer and we determine how the bound-state nucleation depends on the current density and vertical distance between the skyrmions. Finally, we analyzed the robustness of the bound states by considering two situations: 1) a system constituted by clean or homogeneous antiferromagnetic racetracks; 2) a system in which randomly distributed magnetic impurities in both layers are included in the system.