Field-like Perturbation Enabled Six-state Readout in Triaxial $\alpha$-${\mathrm{Fe}}_2{\mathrm{O}}_3$|Pt Bi-layers

Abstract

Canted antiferromagnet $\alpha$-${\mathrm{Fe}}_2{\mathrm{O}}_3$|Pt bilayers offer a platform for multistate memory, but spin Hall magnetoresistance (SMR) readout cannot distinguish states separated by $180^{\circ }$, limiting detection to three states. We show that a field-like perturbation lifts the degeneracy of opposite states in $\alpha$-${\mathrm{Fe}}_2{\mathrm{O}}_3$, enabling the resolution of six states in the SMR signal. We introduce a dual-modulation SMR method to mitigate thermal drifts and enable reliable readout. Computations of first- and second-harmonic SMR reveal the role of exchange, anisotropy and field-like perturbations in resolving the states.

main article: 8 pages, 5 figures and Supplemental material: 7 pages and 6 figures. Revised version with updated figures, improved discussion and modified abstract