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Spin valves of film layer structure, Ta/NiMn/NiFe/Co/Cu/Co/NiFe/Ta/Substrate were fabricated by ion beam sputtering. Optimization of the processes of deposition and posthermal treatment yields highly (111) oriented spin valve films with a giant-magnetoresistance ratio of above 4% and pinning field of 650 Oe. This is the strongest pinning field ever observed. It stays constant up to 180 °C, then decreases to zero at a blocking temperature of 380 °C. These spin valves are highly thermally stable and, thus, suitable for the application of high density recording heads.

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The giant magnetoresistance response of NiMn pinned spin valves was studied at elevated temperature. Top spin valve films were made by ion beam sputtering and thermally treated to induce the strong unidirectional pinning field in the pinned layer. Both ␦R and ␦R/R decrease linearly with temperature. 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 NiMn spin valves. The pinning field has a weakly increasing temperature dependence up to 200°C, then decreases to zero at the blocking temperature of 380°C. Samples with different thickness NiMn layers show different temperature dependencies. However, the blocking temperature is unchanged. The pinning fields of NiMn, FeMn, IrMn, and NiO spin valves were also measured up to 200°C; NiMn pinned spin valves show the least dependence of pinning field at elevated temperatures.