Anisotropic skyrmion bubbles in ultra-thin epitaxial Au$_{0.67}$Pt$_{0.33}$/Co/W films

TL;DR

This study investigates anisotropic magnetic textures, including elliptical skyrmion bubbles, in ultra-thin epitaxial Au$_{0.67}$Pt$_{0.33}$/Co/W films with unique symmetry-induced magnetic anisotropies.

Contribution

It reveals how C$_ ext{2v}$ symmetry causes uniaxial in-plane anisotropy and influences the formation of anisotropic magnetic domains and skyrmion bubbles.

Findings

Formation of magnetic stripe domains aligned with the hard in-plane axis

Elliptical skyrmion bubbles observed in weak out-of-plane fields

Lower domain wall energy along the in-plane axis facilitates these structures

Abstract

We studied the symmetry of magnetic properties and the resulting magnetic textures in ultra-thin epitaxial Au$_{0.67}$Pt$_{0.33}$/Co/W, a model system exhibiting perpendicular magnetic anisotropy and interface Dzyaloshinskii-Moriya interaction (DMI). As a peculiar feature, the C$_\mathrm{2v}$ crystal symmetry induced by the Co/W interface results in an additional uniaxial in-plane magnetic anisotropy in the cobalt layer. Photoemission electron microscopy with magnetic sensitivity reveals the formation of self-organized magnetic stripe domains oriented parallel to the hard in-plane magnetization axis. We attribute this behavior to the lower domain wall energy when oriented along this axis, where both the DMI and the in-plane magnetic anisotropy favor a N\'{e}el domain wall configuration. The anisotropic domain wall energy also leads to the formation of elliptical skyrmion bubbles in a weak out-of-plane magnetic field.