Confinement of Magnetic Skyrmions to Corrals of Artificial Surface Pits with Complex Geometries

Takao Matsumoto,Naoya Shibata

doi:10.3389/fphy.2021.774951

Abstract

Magnetic skyrmion is a particle-like swirling spin texture promising for future memory devices. The geometric confinement and artificial control of skyrmions are crucial for such practical applications. In a previous research, we developed a technique to confine skyrmions to simple geometric corrals, such as a rectangle and a triangle, composed of artificial surface pits with nanometer-scale dimensions fabricated by using a focused electron beam. The technique has a potential advantage of facilitating more complex geometries, which has not been fully explored yet. Here we directly visualize skyrmions confined to surface-pit corrals with several complex geometries by using differential phase contrast scanning transmission electron microscopy. We find that individual skyrmions are deformed not only in shape but also in size under a moderate-bias field. We also find that deformed skyrmionic spin textures with opposite polarities coexist in the zero-field condition. The present study provides a guide to confine skyrmions, which should be useful for future applications.

Highlights

Magnetic skyrmion [1,2,3,4,5] is a particle-like swirling spin texture arising from the competition between Heisenberg and Dzyaloshinskii–Moriya (DM) exchange interactions [6, 7]
A longer pixel dwell time than usual is required at room temperature to record images with sufficient contrast
No contrast indicating the existence of apparent structural defects is observed again in the annular dark-field (ADF) image (Figure 1H), ensuring that the deformations are not induced by structural defects in the specimen

Summary

INTRODUCTION

Magnetic skyrmion [1,2,3,4,5] is a particle-like swirling spin texture arising from the competition between Heisenberg and Dzyaloshinskii–Moriya (DM) exchange interactions [6, 7] It attracts growing attention as it is promising for future innovative devices owing to its nanometer-scale dimensions and topological stability [8, 9]. In a previous study [33], we demonstrated that even tiny surface pits with nanometer-scale dimensions fabricated by using a focused electron beam (surface-pit corral) are effective to confine stable skyrmion states. These unconventional techniques have the potential advantage of facilitating complex geometries that are difficult or even not feasible by conventional microfabrication techniques. We report skyrmion states confined to surface-pit corrals with complex geometries directly visualized in realspace with nanometer spatial resolution by using the DPC STEM technique

MATERIALS AND METHODS

RESULTS AND DISCUSSIONS

DATA AVAILABILITY STATEMENT