Quantitative Study of Current-Induced Effect in an Easy-Plane Antiferromagnet

Luqiao Liu, MIT

April 24, 2020

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).