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 degrees C. Values of Delta R/R, R, and coercivities were found to be reversible up to 200 degrees C. Irreversible changes in transport properties observed at and above 250 degrees 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.