Thermal annealing study of spin valves

Abstract

The thermal stability of spin valves was studied through measuring the magnetoresistance response curves at different temperatures with the applied field set at different angles from the pinning field direction. According to a simple coherent rotation model, the magnetoresistance versus applied field curves should be symmetrical with respect to the zero field line when the applied field is perpendicular to the pinning field. The deviation from symmetry should be attributed to the canting of the pinning field direction. The deviation from symmetry should be attributed to the canting of the pinning field direction. Experiments have been carried out on spin valves with a structure of SiASiO2/Ta(2nm)/Ni80Fe20(2.5nm)/CoFe(1 nm)/Cu(2 nm)/CoFe(2 nm)/IrMn(5 nm)/Ta(2 nm). The canting of the pinning field was seen clearly from the change of the magnetoresistance curves while the temperature was varied from 50 to 100°C. A quantity (the relative change in the asymmetry of the response curve) was newly defined to estimate the temperature window for the onset of the canting process. © 2001 American Institute of Physics.