Angular and NiFe thickness dependence of IrMn/NiFe/IrMn thin films

The variation in exchange bias as a function of FM layer in FM/AFM/FM trilayer structure using IrMn(100 /spl Aring/)/NiFe(t /spl Aring/)/IrMn(100 /spl Aring/) thin films is reported. Unidirectional exchange anisotropy and the uniaxial anisotropy were analysed by ferromagnetic resonance (FMR) measurements. The angular variation in resonance field, as a function of the NiFe layer thickness, manifests a unidirectional behavior for the exchange biased thin film. The variation of the unidirectional anisotropy field (H/sub ex/) and uniaxial anisotropy field (H/sub k/) with NiFe thickness was also determined. Results show that H/sub ex/ and H/sub k/ decreases linearly as NiFe thickness increases. When NiFe thickness reaches 800 /spl Aring/, however, the trend becomes nonlinear which indicates that the uniform magnetization distribution throughout NiFe layers is preserved up to NiFe thickness of 400 /spl Aring/. The H/sub ex/ of thicker NiFe layers could be from an inhomogeneous NiFe magnetization reversal due to domain formation in NiFe layer.