Anomalous properties of spin valves at elevated temperatures

We present results of magnetoresistance measurements on a 50 nm NiO/2.7 nm Co/2.2 nm Cu/3.1 nm Co/2.5 nm Au spin valve performed in vacuum at temperatures up to 400°C. Values of ΔR/R, R, and coercivities were found to be reversible up to 200°C. Irreversible changes in transport properties observed at and above 250°C were concurrent with changes in the interlayer coupling. A striking result is that the coercivity of the NiO-coupled Co film remains large for temperatures at and above the Neel temperature of NiO. Evidence is presented for the existence of `coercivity transfer´ between the Co layers