Nanjing Univ, Dept Phys, Solid State Microstruct Lab, Nanjing 210093, Peoples R China
; Sci Acad China, BSRF, Inst High Energy Phys, Beijing 100039, Peoples R China
We have fabricated two sets of NiO-Co-Cu based spin valves by the magnetosputtering technique with different deposition parameters. Magnetoresistance (MR) measurements show that the MR value for the NiO layer under the bottom of Co/Cu/Co spin valve (BSV) is larger than that for the NiO layer at the top of Co/Cu/Co (TSV). The MR value of BSV decreases with increasing annealing temperature in air or in vacuum, which disappears at the blocking temperature of NiO, i.e., about 250 degrees C. There is maximum MR value for TSV annealing at a temperature range from room temperature to 350 degrees C. The different thermal behavior for BSV and TSV is explained by the competition between the interface roughness of NiO/Co, which was determined by the grazing incident X-ray reflectivity and X-ray diffuse scattering, and the coupling effect between Co layer and NiO layer.