Nanomagnetism of magnetoelectric granular thin-film antiferromagnets

TL;DR

This paper demonstrates the use of single-spin magnetometry to image and analyze nanoscale antiferromagnetic domains in Cr₂O₃ thin films, providing new insights into their magnetic properties and domain formation.

Contribution

It introduces a novel application of single-spin magnetometry combined with transport experiments to study nanoscale antiferromagnetic thin films.

Findings

Real-space imaging of individual antiferromagnetic domains

Identification of domain formation mechanisms

Measurement of exchange coupling strength between grains

Abstract

Antiferromagnets have recently emerged as attractive platforms for spintronics applications, offering fundamentally new functionalities compared to their ferromagnetic counterparts. While nanoscale thin film materials are key to the development of future antiferromagnetic spintronics technologies, experimental tools to explore such films on the nanoscale are still sparse. Here, we offer a solution to this technological bottleneck, by addressing the ubiquitous surface magnetisation of magnetoelectic antiferromagnets in a granular thin film sample on the nanoscale using single-spin magnetometry in combination with spin-sensitive transport experiments. Specifically, we quantitatively image the evolution of individual nanoscale antiferromagnetic domains in 200-nm thin-films of Cr$_2$O$_3$ in real space and across the paramagnet-to-antiferromagnet phase transition. These experiments allow us to discern key properties of the Cr$_2$O$_3$ thin film, including the mechanism of domain formation and the strength of exchange coupling between individual grains comprising the film. Our work offers novel insights into Cr$_2$O$_3$'s magnetic ordering mechanism and establishes single spin magnetometry as a novel, widely applicable tool for nanoscale addressing of antiferromagnetic thin films.