Control of Spin Hall Magnetoresistance by Néel Vector in Pt/Co/NiO Multilayers

Spin Hall magnetoresistance (SMR) in bilayer systems comprising a heavy metal (HM) and a ferromagnet (FM) is essential for understanding of spin transport mechanism and developing next-generation magnetic memory technologies. However, it remains challenging to control the SMR in HM/FM bilayers without changing the HM/FM interface quality. In this work, this is reported that the Néel vector from high-quality epitaxial NiO(001) thin films can effectively modulate SMR in Pt/Co bilayers. The findings indicate that the SMR is sensitive to the direction of the Néel vector of NiO, which can be significantly modified by the thickness of the NiO layer. Notably, a sign change of SMR is observed in the multilayers with a thinner NiO layer when the temperature is lowered to certain thresholds. This is further reveals that with the changing of the Néel vector direction, the reflection of spin current at the Co/NiO interface can effectively modify the sign and the magnitude of SMR. Based on this mechanism, the negative SMR at room temperature is achieved in multilayers with ultrathin Co and NiO layers. This study presents a novel strategy for effectively controlling SMR in HM/FM systems, which can be useful for the development of high-performance SMR-based spintronic devices.