Regular and in-plane skyrmions and antiskyrmions from boundary instabilities

TL;DR

This paper develops a theory for generating skyrmions and antiskyrmions at boundaries using magnetic field and current pulses, highlighting boundary instabilities and the role of Dzyaloshinskii-Moriya interaction.

Contribution

It introduces a novel boundary-based mechanism for skyrmion and antiskyrmion creation involving kink solutions and localized magnon mode instabilities.

Findings

Boundary instabilities can generate topological defects.

Magnetization twists near edges can lead to skyrmion formation.

Proper current direction can control defect generation and movement.

Abstract

We formulate a theory of skyrmion and antiskyrmion generation using magnetic field and charge current pulses. We show that the topological defect can be created at an edge of a system with Dzyaloshinskii-Moriya interaction (DMI) as well as at a boundary between regions with different DMI. We consider both perpendicular and in-plane (also known as magnetic bimerons) versions of skyrmions and antiskyrmions. We show that the magnetization twist in the vicinity of an edge or a boundary is described by a kink solution, the presence of which can instigate the generation of topological defects. We study the collective excitations of magnetization analytically and numerically, and demonstrate that under application of magnetic field and charge current pulses the magnon modes localized near boundaries can develop instabilities leading to the formation of skyrmions or antiskyrmions. Due to the skyrmion and antiskyrmion Hall effects, a properly chosen current direction can push the topological defects away from the boundary, thus facilitating their generation.