Reliable Electrical Switching of Tri-State Antiferromagnetic Néel Order in <i>a</i>-Fe₂O₃ Epitaxial Films

Ability to manipulate antiferromagnetic (AF) moments is a key requirement for the emerging field of antiferromagnetic spintronics. Electrical switching of bi-state AF moments has been demonstrated in metallic AFs, CuMnAs and Mn₂Au. Recently, current-induced “saw-tooth” shaped Hall resistance was reported in Pt/NiO bilayers, while its mechanism is under debate. Here, we report the first demonstration of convincing, non-decaying, step-like electrical switching of tri-state Néel order in Pt/a-Fe₂O₃ bilayers. Our experimental data shows the switching behavior of a-Fe₂O₃ Néel order among three stable states, which can be detected by the change of Hall resistance ΔR_xy through spin Hall anomalous Hall effect (SH-AHE). We also show that the observed “saw-tooth” Hall resistance is due to an artifact of Pt, not AF switching, while the signature of AF switching is step-like Hall signals. Together with the Monte-Carlo simulations, we reveal the clear mechanism of AF Néel order switching and explain why only the first current pulse switches the Néel order. This demonstration of electrical control of magnetic moments in AF insulator (AFI) films will greatly expand the scope of AF spintronics by leveraging the large family of AFIs.