Nanoscale imaging of antiferromagnetic domains in epitaxial films of Cr2O3 via scanning diamond magnetic probe microscopy

TL;DR

This study uses diamond nitrogen vacancy microscopy to directly image antiferromagnetic domains and boundary magnetization in Cr2O3 thin films, revealing domain formation, degeneracy lifting via magnetic fields, and reversible edge magnetic states.

Contribution

It demonstrates a novel application of diamond NV microscopy for imaging antiferromagnetic domains and boundary magnetization in epitaxial Cr2O3 films, including control of domain states.

Findings

Correlation between magnetic domain size and structural grain size

Degeneracy of 180° domains can be lifted with magnetic fields during cooling

Reversible edge magnetic states observed with nanostructuring

Abstract

We report direct imaging of boundary magnetization associated with antiferromagnetic domains in magnetoelectric epitaxial Cr2O3 thin films using diamond nitrogen vacancy microscopy. We found a correlation between magnetic domain size and structural grain size which we associate with the domain formation process. We performed field cooling, i.e., cooling from above to below the N\'eel temperature in the presence of magnetic field, which resulted in the selection of one of the two otherwise degenerate 180 degree domains. Lifting of such a degeneracy is achievable with a magnetic field alone due to the Zeeman energy of a weak parasitic magnetic moment in Cr2O3 films that originates from defects and the imbalance of the boundary magnetization of opposing interfaces. This boundary magnetization couples to the antiferromagnetic order parameter enabling selection of its orientation. Nanostructuring the Cr2O3 film with mesa structures revealed reversible edge magnetic states with the direction of magnetic field during field cooling.