Observation of stable Neel skyrmions in Co/Pd multilayers with Lorentz transmission electron microscopy

TL;DR

This study demonstrates the direct imaging of stable Neel skyrmions at room temperature in Co/Pd multilayers using Lorentz transmission electron microscopy, revealing detailed internal spin structures without external stabilizing fields.

Contribution

It provides the first direct visualization and internal spin structure mapping of Neel skyrmions in thick multilayers at room temperature using Lorentz TEM.

Findings

Neel skyrmions observed at room temperature in Co/Pd multilayers.

Internal spin structure mapped with phase retrieval techniques.

Skyrmions stabilized without external out-of-plane magnetic fields.

Abstract

Neel skyrmions are of high interest due to their potential applications in a variety of spintronic devices, currently accessible in ultrathin heavy metal/ferromagnetic bilayers and multilayers with a strong Dzyaloshinskii-Moriya interaction. Here we report on the direct imaging of chiral spin structures including skyrmions in an exchange coupled Co/Pd multilayer at room temperature with Lorentz transmission electron microscopy, a high resolution technique previously suggested to exhibit no Neel skyrmion contrast. Phase retrieval methods allow us to map the internal spin structure of the skyrmion core, identifying a 25 nm central region of uniform magnetization followed by a larger region characterized by rotation from in- to out-of-plane. The formation and resolution of the internal spin structure of room temperature skyrmions without a stabilizing out-of-plane field in thick magnetic multilayers opens up a new set of tools and materials to study the physics and device applications associated with chiral ordering and skyrmions.