Estimate of crystalline anisotropy by using the asymmetric AMR curve in NiO/NiFe bilayer

Anisotropic magnetoresistance(AMR) curves were measured as functions of the angle between the applied and the exchange coupling fields in bilayer NiO/NiFe(x)(x=50, 100, 200, and 300 A), and the data were compared with the results from calculations using the single-domain model with uniaxial crystalline anisotropy. The AMR was asymmetric for an applied field less than the exchange coupling field. The maximum MR in the asymmetric AMR was observed at a negative angle(clockwise rotation) from the exchange coupling field in the 50 and 100 Å samples, but at a positive angle in the 300 Å sample. Such a variation of the AMR can be explained well by a change in the value of the uniaxial anisotropy field from positive to negative as the NiFe thickness increases, as well as by its angle from the exchange coupling field. This suggests that the characteristics of crystalline anisotropy originating from the fabrication can be estimated from AMR measurements.