Structure and interface characterisation of Exchange Bias FeMn-FeNi films

X-ray and neutron scattering studies have been carried out on thermally evaporated FeMn-FeNi exchange bias systems before and after ion irradiation by helium ions. Helium ion dosages of 10^14 - 1017 ions /cm-2 have been used. The ion irradiation has shown to alter the exchange bias characteristics of the samples with dose and rate. X-ray diffraction measurements on the samples were made to assess the epitaxy of the layers to the substrate. In order to assess the effect of ion irradiation on these films, both neutron and x-ray reflectivity measurements were performed and the data modelled simultaneously. A final model was chosen that approximated both sets of data well. The reflectivity data suggest that the samples are prone to etching of the surface layer by the ions and that ion irradiation encourages interlayer mixing resulting in a smearing of the oscillations. Increased ion dosages result in a complete loss of exchange bias properties which is supported with loss in inter-layer definition by ion irradiation.