Spin Hall magnetoresistance and unidirectional magnetoresistance in ferromagnet metal/antiferromagnet insulator bilayers

Abstract

The spin Hall effect (SHE) and its inverse effect have opened up broad opportunities for the study and practical applications of spintronics. Spin Hall magnetoresistance (SMR) and unidirectional magnetoresistance (UMR) are examples of the SHE effects that alter electrical resistance in ferromagnet metal (FM)/heavy metal (HM) bilayers, depending on the relative direction of magnetization in ferromagnet and the flow of charge current1,2. This is due to the spin injection from the HM and the magnetization-dependent spin scattering of conduction electrons at the interface, leading to the magnetization-dependent inverse spin Hall effect (ISHE) and, accordingly, magnetization-dependent electric resistance3,4. Intriguingly, from the present study, we find that these phenomena can occur within a single ferromagnetic metal in contact with an antiferromagnetic insulator (AFI), where the combined processes of self-generation of spin currents in the FM and magnonic spin dissipation from the AFI lead to the appearance of both SMR and UMR. From systematic studies, we further reveal that the measured SMR and UMR in FM/AFI are highly related to magnon states in the AFM layer. These findings provide insights into spin-dependent transport phenomena for spintronics devices, contributing to the development of new applications in this field.