Unveiling the three-dimensional spin texture of skyrmion tubes

TL;DR

This paper introduces a novel holographic vector field electron tomography technique to quantitatively reconstruct the three-dimensional spin texture of skyrmion tubes at nanometer resolution, revealing complex internal structures and surface effects.

Contribution

It is the first to experimentally determine the 3D spin texture of skyrmions with sub-10 nanometer resolution, uncovering detailed internal deviations and surface collapse phenomena.

Findings

Revealed previously unseen local deviations from homogeneous Bloch character within skyrmion tubes

Observed the collapse of skyrmion textures at surfaces

Mapped the magnetic energy density across skyrmions

Abstract

Magnetic skyrmions are stable topological solitons with complex non-coplanar spin structures. Their nanoscopic size and the low electric currents required to initiate and control their motion has opened a new field of research, skyrmionics, that aims at using skyrmions as information carriers for data storage and manipulation. Recent advances in skyrmionics prompt for a thorough understanding of the detailed three-dimensional (3D) spin texture of a skyrmion including skyrmion-skyrmion interactions and their coupling to surfaces and interfaces. These properties crucially affect application-related aspects such as the stability and mobility of skyrmions in confined structures. To date, however, experimental techniques to measure the three-dimensional spin texture with nanometer resolution are largely missing. We therefore adapt holographic vector field electron tomography to the problem and report on the first quantitative reconstruction of the 3D spin texture of skyrmions with sub-10 nanometer resolution. The reconstructed textures reveal a variety of previously unseen local deviations from a homogeneous Bloch character within the skyrmion tubes (SkTs), details of the collapse of the skyrmion texture at surfaces, and a correlated modulation of the SkT in FeGe along their tube axes. The quantitative 3D data of the magnetic induction also allow to experimentally confirm some principles of skyrmion formation by deriving spatially resolved maps of the magnetic energy density across these magnetic solitons.