The tunneling magnetoresistance ratio of a magnetic tunnelling junction is influenced by many different factors, one of which is hybridization at the metal/oxide interface. We have recently investigated tunnel barrier structures with HfO2 by polarized neutron reflectometry studying how hybridization at the metal/oxide interface affects the magnetic moment, finding agreement with theoretical calculations. We have also recently undertaken a study of EuO interfaces with Si and Pt which we are still analyzing. This proposal would allow us also a direct comparison with the previous results. We want to use a spin filtering EuO barrier to achieve single electron spin detection, a question important for quantum computing. We propose to study EuO in contact with different metals, both magnetic and non magnetic: Co, CoFe, Fe, Cu and Y. This would allow us to study the metal/oxide hybridization.