Spin-orbit torque in antiferromagnetically coupled Co and Tb multilayers

Abstract

We report the enhancement of spin–orbit torque (SOT) in Pt/Co/Pt and Pt/Co/AlOx multilayers by inserting rare-earth metal Tb layer. The inserted Tb layer thickness dependence of the critical switching current indicates that thicker Tb layer lead to more enhancement. The higher efficiency of SOT can be attributed to the increase of the effective spin Hall angle after inserting Tb layer, which has also been proved through the spin Hall magnetoresistance measurement. The temperature dependence of anomalous Hall effect and remanent magnetization reveals that the Pt/Co/Tb (2 nm)/AlOx sample is antiferromagnetically coupled below 320 K. The behavior of the temperature dependent SOT effective fields and effective spin Hall angle in the Pt/Co/Tb (2 nm)/AlOx sample have also been investigated, which increase substantially when temperature decreased from 300 to 100 K. We suggest that the significant increase of SOT efficiency is ascribed to the antiferromagnetically coupled Co and Tb layer.