Physical origins of the magnetoresistance of platinum in contact with polycrystalline antiferromagnetic NiO

Abstract

Abstract We report measurements of the magnetoresistance (MR) of platinum in Pt/NiO bilayers made with well textured NiO polycrystalline films over a wide temperature range. We show that the MR arises from two sources, the spin Hall magnetoresistance (SMR) and the anisotropic magnetoresistance (AMR). The latter results from the magnetic proximity effect of Pt in atomic contact with one of the antiferromagnetic NiO sublattices. The SMR is produced by the charge current generated in the Pt layer by the spin current back reflected from the antiferromagnetic insulating (AFI) NiO film through the inverse spin Hall effect (ISHE). As previously observed in Pt with NiO in the form of bulk crystals or epitaxial films, here the SMR exhibits oscillations in the field angle variation shifted by 90° relative to that observed in the insulating ferrimagnet yttrium iron garnet (YIG). Measurements in the temperature range 10–300 K show that the SMR increases with temperature while the AMR remains constant. The total magnetoresistance of Pt/NiO measured at room temperature with well textured NiO polycrystalline films is substantially larger than the values reported for crystalline or epitaxial NiO.