Origin of large spin Hall magnetoresistance in Fe/CuOx bilayers

Abstract We have compared the spin Hall magnetoresistance (SMR) in Fe/Pt and Fe/CuOx (with natural oxidation) bilayers with varying the thickness of Fe layer. A larger SMR in Fe/CuOx bilayers has been found when the thickness of Fe layer is 3 nm. Moreover, the SMR of the two bilayers decrease with increasing the thickness of Fe from 3 nm to 10 nm, but that of Fe/CuOx drops more sharply due to shunting current effect. Through harmonic measurements, the emergent spin current is proved to be generated in the Fe/CuOx bilayers. The mixed phase of CuOx has been confirmed including CuO, Cu2O and Cu, which performs strong spin-orbit coupling and produce large spin current. On the other hand, the interface-generated spin current should be ruled out. All the results have been compared with those in Fe/Al2O3 bilayers with negligible spin current.