Co-existence of Bloch and Neel walls in a collinear antiferromagnet

TL;DR

This study uses advanced microscopy techniques to analyze the structure and properties of domain walls in the antiferromagnet Cr₂O₃, revealing coexistence of Bloch and Néel walls and their characteristics.

Contribution

It provides the first detailed experimental characterization of Bloch and Néel domain walls in a collinear antiferromagnet, including their coexistence, chirality, and quantitative measurements.

Findings

180° domain walls are mainly Bloch-like

Néel walls can coexist with Bloch walls in certain crystals

Quantitative measurements of domain-wall width and surface magnetization

Abstract

We resolve the domain-wall structure of the model antiferromagnet $\text{Cr}_2\text{O}_3$ using nanoscale scanning diamond magnetometry and second-harmonic-generation microscopy. We find that the 180$^\circ$ domain walls are predominantly Bloch-like, and can co-exist with N\'eel walls in crystals with significant in-plane anisotropy. In the latter case, N\'eel walls that run perpendicular to a magnetic easy axis acquire a well-defined chirality. We further report quantitative measurement of the domain-wall width and surface magnetization. Our results provide fundamental input and an experimental methodology for the understanding of domain walls in pure, intrinsic antiferromagnets, which is relevant to achieve electrical control of domain-wall motion in antiferromagnetic compounds.