Quantifying Spin-Orbit Torques in Antiferromagnet/Heavy Metal Heterostructures

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 (SOTs) 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-Fe2O3 films, with an interface to Pt. By modeling the harmonic Hall signals together with the α-Fe2O3 magnetic parameters, we determine the amplitudes of fieldlike and dampinglike SOTs. Out-of- plane field scans are shown to be essential to determining the dampinglike component of the torques. In contrast to ferromagnetic–heavy-metal heterostructures, our results demonstrate that the fieldlike torques are significantly larger than the dampinglike 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 SOTs in AFM-HM heterostructures.

This article has been published in Physical Review Letters and is available here.