Geometrically stabilized skyrmionic vortex in FeGe tetrahedral nanoparticles.

Kodai Niitsu,Alexander C Booth,Naoto Nagaosa,Yoshinori Tokura,Nitish Mathur,Daisuke Shindo,Yizhou Liu,Matthew J Stolt,Jiadong Zang,Xiuzhen Yu,Song Jin

doi:10.1038/s41563-021-01186-x

Abstract

The concept of topology has dramatically expanded the research landscape of magnetism, leading to the discovery of numerous magnetic textures with intriguing topological properties. A magnetic skyrmion is an emergent topological magnetic texture with a string-like structure in three dimensions and a disk-like structure in one and two dimensions. Skyrmions in zero dimensions have remained elusive due to challenges from many competing orders. Here, by combining electron holography and micromagnetic simulations, we uncover the real-space magnetic configurations of a skyrmionic vortex structure confined in a B20-type FeGe tetrahedral nanoparticle. An isolated skyrmionic vortex forms at the ground state and this texture shows excellent robustness against temperature without applying a magnetic field. Our findings shed light on zero-dimensional geometrical confinement as a route to engineer and manipulate individual skyrmionic metastructures.

Highlights

The Dzyaloshinskii–Moriya interaction has provided a vast playground to tailor topological states in magnetic systems
One of the most remarkable advances has been the discovery of magnetic skyrmions, which are topological swirling spin configurations that are typically stabilized in material systems with broken inversion symmetry3-5
We developed and performed multi-angle electron holography (EH) on chemically-synthesized isolated tetrahedral nanoparticles of B20-type FeGe to reveal the internal 3D magnetic configurations

Summary

Introduction

The Dzyaloshinskii–Moriya interaction has provided a vast playground to tailor topological states in magnetic systems. One of the most remarkable advances has been the discovery of magnetic skyrmions, which are topological swirling spin configurations that are typically stabilized in material systems with broken inversion symmetry3-5 Their topological-particle like nature in two dimensions and the extremely low critical current density needed to drive their motion have potential for manipulating individual skyrmions in future spintronic devices. Larger nanoparticles reasonably host the helimagnetic ground state, nanoparticles with sizes comparable to the helical wavelength [~70 nm for FeGe20] lead to the emergence of a novel skyrmionic vortex structure, revealing the topological nature of a skyrmion string. The projected magnetic configuration along the [001 ] direction (Fig. 2l) resembles a vortex state with unity vorticity, in which in-plane magnetic moments rotate by an angle of 2π circulating around the center. Its slight deviation from 1 is mainly attributed to the entanglement with corner spin twists at the boundary of the skyrmionic vortex

Methods

Conclusion