Magnetic microscopy of topologically protected homochiral domain walls in an ultrathin perpendicularly magnetized Co film

TL;DR

This paper uses Lorentz transmission electron microscopy to directly image homochiral Neel domain walls in ultrathin Co films, highlighting their potential for high-density data storage due to their topological protection.

Contribution

It provides direct imaging evidence of homochiral Neel domain walls in Pt/Co/AlO$_x$ films, demonstrating their topological protection and relevance for memory devices.

Findings

Presence of homochiral Neel domain walls confirmed

Domain walls are topologically protected

Potential for dense data storage applications

Abstract

Next-generation concepts for solid-state memory devices are based on current-driven domain wall propagation, where the wall velocity governs the device performance. It has been shown that the domain wall velocity and the direction of travel is controlled by the nature of the wall and its chirality. This chirality is attributed to effects emerging from the lack of inversion symmetry at the interface between a ferromagnet and a heavy metal, leading to an interfacial Dzyaloshinskii-Moriya interaction that can control the shape and chirality of the magnetic domain wall. Here we present direct imaging of domain walls in Pt/Co/AlO$_x$ films using Lorentz transmission electron microscopy, demonstrating the presence of homochiral, and thus topologically protected, N\'{e}el walls. Such domain walls are good candidates for dense data storage, bringing the bit size down close to the limit of the domain wall width.