Magnetic microscopy and topological stability of homochiral Néel domain walls in a Pt/Co/AlOx trilayer

M J Benitez,G Burnell,C H Marrows,T A Moore,A P Mihai,D Mcgrouther,S Mcvitie,A Hrabec

doi:10.1038/ncomms9957

M J Benitez, G Burnell + Show 6 more

Open Access

https://doi.org/10.1038/ncomms9957

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Journal: Nature Communications	Publication Date: Dec 1, 2015
Citations: 130	License type: CC BY 4.0

Affiliation: University of Glasgow, University of Leeds

Abstract

The microscopic magnetization variation in magnetic domain walls in thin films is a crucial property when considering the torques driving their dynamic behaviour. For films possessing out-of-plane anisotropy normally the presence of Néel walls is not favoured due to magnetostatic considerations. However, they have the right structure to respond to the torques exerted by the spin Hall effect. Their existence is an indicator of the interfacial Dzyaloshinskii–Moriya interaction (DMI). Here we present direct imaging of Néel domain walls with a fixed chirality in device-ready Pt/Co/AlOx films using Lorentz transmission electron and Kerr microscopies. It is shown that any independently nucleated pair of walls in our films form winding pairs when they meet that are difficult to annihilate with field, confirming that they all possess the same topological winding number. The latter is enforced by the DMI. The field required to annihilate these winding wall pairs is used to give a measure of the DMI strength. Such domain walls, which are robust against collisions with each other, are good candidates for dense data storage.

Highlights

The microscopic magnetization variation in magnetic domain walls in thin films is a crucial property when considering the torques driving their dynamic behaviour
The Dzyaloshinskii–Moriya interaction (DMI) strength is imprinted into the static domain walls (DWs) texture via a virtual effective magnetic field that prefers a Neel wall of a given chirality rather than the magnetostatically favoured Bloch wall[3]
We use Lorentz transmission electron microscopy31 (L-TEM) and Kerr microscopy to directly image DWs in perpendicularly magnetized device-ready films of Pt/Co/AlOx, allowing us to deduce the presence of narrow homochiral—that is, possessing the same soliton winding number—Neel walls

Summary

Introduction

The microscopic magnetization variation in magnetic domain walls in thin films is a crucial property when considering the torques driving their dynamic behaviour. The DMI strength is imprinted into the static DW texture via a virtual effective magnetic field that prefers a Neel wall of a given chirality rather than the magnetostatically favoured Bloch wall[3].

Results

Conclusion