Role of substrate clamping on anisotropy and domain structure in the canted antiferromagnet $\alpha$-Fe$_2$O$_3$

TL;DR

This study explores how substrate clamping influences domain structures and anisotropy in $ ext{Fe}_2 ext{O}_3$, revealing isotropic domain distributions and unique magnetic field responses relevant for spintronics applications.

Contribution

It demonstrates that substrate clamping causes anisotropy fluctuations and isotropic domain distributions in $ ext{Fe}_2 ext{O}_3$, providing new insights into antiferromagnetic thin film behavior.

Findings

Destressing fields fluctuate due to substrate clamping.

Domain distribution becomes isotropic despite crystal symmetry.

Weak ferromagnetism affects magnetic field dependence.

Abstract

Antiferromagnets have recently been propelled to the forefront of spintronics by their high potential for revolutionizing memory technologies. For this, understanding the formation and driving mechanisms of the domain structure is paramount. In this work, we investigate the domain structure in a thin-film canted antiferromagnet $\alpha$-Fe$_2$O$_3$. We find that the internal destressing fields driving the formation of domains do not follow the crystal symmetry of $\alpha$-Fe$_2$O$_3$, but fluctuate due to substrate clamping. This leads to an overall isotropic distribution of the N\'eel order with locally varying effective anisotropy in antiferromagnetic thin films. Furthermore, we show that the weak ferromagnetic nature of $\alpha$-Fe$_2$O$_3$ leads to a qualitatively different dependence on magnetic field compared to collinear antiferromagnets such as NiO. The insights gained from our work serve as a foundation for further studies of electrical and optical manipulation of the domain structure of antiferromagnetic thin films.