Electrical control and detection of magnetic ordering inside antiferromagnets has attracted considerable interests, for potential advantages in operating speed and device densities. Unlike ferromagnets, where the current-induced spin torque can be calibrated with the effect from an external magnetic field, a quantitative relationship between the detected electrical signal and the magnitude of spin torque in antiferromagnets remains to be established. In this talk, I will show that by utilizing an antiferromagnetic insulator with Dzyaloshinskii-Moriya interaction, α-Fe2O3, we can control Néel vectors with a small external magnetic field, which can be further utilized as a standard to calibrate current-induced magnetic dynamics [1].

First of all, we found that the saw-tooth like switching patterns in the spin Hall magnetoresistance, as has been studied before in other antiferromagnetic insulators, does not necessarily correspond to real magnetic re-orientations, but instead can have a pure resistive origin. By carrying out a systematic study on the dependence of device size and film thickness, we are able to identify the two main contributions from current onto real magnetic dynamics: the thermally induced magnetoelastic effect and the field-like spin-orbit torque. We found that the magnetoelastic effect plays a dominant role in the magnetic switching of Pt/ α-Fe2O3. It is also expected that the thermally induced magnetoelastic effect can exist and make significant contributions in other easy-plane antiferromagnets with moderate magnetostrictive coefficient.

[1] P. Zhang, J. Finley, T. Safi and L. Liu, Quantitative Study on Current-Induced Effect in an Antiferromagnet Insulator/Pt Bilayer Film, Phys. Rev. Lett. 123, 247206 (2019).