Current-induced switching of thin film $\alpha$-Fe$_2$O$_3$ devices imaged using a scanning single-spin microscope

TL;DR

This study uses a diamond NV center scanning microscope to image and analyze current-induced magnetic switching in thin film $ ext{α-Fe}_2 ext{O}_3$ devices, revealing anisotropy effects and switching dependencies on current parameters.

Contribution

It provides the first detailed magnetic imaging of current-induced switching in $ ext{α-Fe}_2 ext{O}_3$ using NV center microscopy, highlighting anisotropy and switching efficiency factors.

Findings

Magnetic textures are stronger along specific crystallographic directions.

Switching efficiency depends on current pulse duration, amplitude, and direction.

In-plane uniaxial anisotropy is observed despite expected 3-fold symmetry.

Abstract

Electrical switching of N\'eel order in an antiferromagnetic insulator is desirable as a basis for memory applications. Unlike electrically-driven switching of ferromagnetic order via spin-orbit torques, electrical switching of antiferromagnetic order remains poorly understood. Here we investigate the low-field magnetic properties of 30 nm thick, c-axis oriented $\alpha$-Fe$_2$O$_3$ Hall devices using a diamond nitrogen-vacancy (NV) center scanning microscope. Using the canted moment of $\alpha$-Fe$_2$O$_3$ as a magnetic handle on its N\'eel vector, we apply a saturating in-plane magnetic field to create a known initial state before letting the state relax in low field for magnetic imaging. We repeat this procedure for different in-plane orientations of the initialization field. We find that the magnetic field images are characterized by stronger magnetic textures for fields along $[\bar{1}\bar{1}20]$ and $[11\bar{2}0]$, suggesting that despite the expected 3-fold magneto-crystalline anisotropy, our $\alpha$-Fe$_2$O$_3$ thin films have an overall in-plane uniaxial anisotropy. We also study current-induced switching of the magnetic order in $\alpha$-Fe$_2$O$_3$. We find that the fraction of the device that switches depends on the current pulse duration, amplitude and direction relative to the initialization field. Specifically, we find that switching is most efficient when current is applied along the direction of the initialization field.