Temperature dependence of giant magnetoresistance properties of NiMn pinned spin valves

The giant magnetoresistance response of NiMn pinned spin valves was studied at elevated temperature. Top spin valve films were made by ion beam sputte ring and thermally treated to induce the strong unidirectional pinning fiel d in the pinned layer. Both delta R and delta R/R decrease linearly with te mperature. The sheet resistance of the spin valves also increases linearly with temperature. The exchange coupling between pinned layer and free layer decreases slightly and the coercivity of the free layer increases slightly . The temperature dependence of the exchange pinning field is unique in NiM n spin valves. The pinning field has a weakly increasing temperature depend ence up to 200 degrees C, then decreases to zero at the blocking temperatur e of 380 degrees C. Samples with different thickness NiMn layers show diffe rent temperature dependencies. However, the blocking temperature is unchang ed. The pinning fields of NiMn, FeMn, IrMn, and NiO spin valves were also m easured up to 200 degrees C; NiMn pinned spin valves show the least depende nce of pinning field at elevated temperatures. (C) 1998 American Institute of Physics.