Magnetization Processes in Exchange-Biased MnPd/ Fe Bilayers Studied by Polarized Neutron Reflectivity

The magnetization processes in exchange-biased MnPd/Fe bilayers have been investigated using polarized neutron reflectivity and vibrating sample magnetometry. The measurements show that by breaking the symmetry of the intrinsic cubic fourfold anisotropy of the Fe film the induced unidirectional anisotropy radically changes the magnetization processes. If the exchange bias is large the induced unidirectional anisotropy is able to pull the net magnetization of the sample to the bias direction after saturation along any of the magnetic hard Fe〈110〉 directions. However, if the exchange bias is small it will only give rise to a difference in net magnetization along the magnetic easy axes adjacent to the saturation direction. Thus, the net magnetic moment along the bias direction depends on the relative magnitudes of the cubic and the unidirectional anisotropies.