Quantifying Spin-Orbit Torques in Antiferromagnet-Heavy-Metal Heterostructures.

• DOI: 10.48550/arxiv.2112.12238
• Publication Date: 2022-06-17
• Authors: Egecan Cogulu; Hantao Zhang; Nahuel N. Statuto; Yang Cheng; Fengyuan Yang; Ran Cheng; Andrew D. Kent
• Keywords: Condensed Matter - Mesoscale and Nanoscale Physics; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); 0103 physical sciences; FOS: Physical sciences; 01 natural sciences

The effect of spin currents on the magnetic order of insulating antiferromagnets (AFMs) is of fundamental interest and can enable new applications. Toward this goal, characterizing the spin-orbit torques (SOT) associated with AFM/heavy metal (HM) interfaces is important. Here we report the full angular dependence of the harmonic Hall voltages in a predominantly easy-plane AFM, epitaxial c-axis oriented $α$-Fe$_2$O$_3$ films, with an interface to Pt. By modeling the harmonic Hall signals together with the $α$-Fe$_2$O$_3$ magnetic parameters, we determine the amplitudes of field-like and damping-like SOT. Out-of-plane field scans are shown to be essential to determining the damping-like component of the torques. In contrast to ferromagnetic/heavy metal heterostructures, our results demonstrate that the field-like torques are significantly larger than the damping-like torques, which we correlate with the presence of a large imaginary component of the interface spin-mixing conductance. Our work demonstrates a direct way of characterizing SOT in AFM/HM heterostructures.