Thermal stability of spin valve with NiO/α-Fe2O 3 bilayer antiferromagnets

To enhance the thermal stability of the NiO pinning layers for spin valves, α-Fe₂O₃ layers, of which the Neel temperature is 680°C for bulk, are deposited on NiO layers. With 15-80 Å thick α-Fe₂O₃ layers on NiO layers, an exchange anisotropy field about five times larger than that of NiO/NiFe is obtained after 250°C thermal annealing. Spin valve multilayers with NiO/α-Fe₂O₃ antiferromagnets show about 12% MR ratio. After 150°C annealing, the MR ratio changes less than 20% for patterned spin valve multilayers with abutted junctioned hard magnets