Chemical structure and magnetism of feo_x/fe₂o₃ interface studied by x-ray absorption spectroscopy

The chemical and magnetic states of Fe/Fe₂O₃ thin films prepared by e-beam evaporation were investigated by using element-specific techniques, X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). It was clearly shown that the Fe layers are oxidized to form an antiferromagnetic (AFM) FeO_x<1, while the bottom oxide remained a weak ferromagnet (wFM) (α+γ)-type Fe₂O₃. Dependences of the peak intensities and lineshapes on the Fe thickness and measurement geometry further demonstrate that FeO_x<1 layers reside mostly at the interface realizing an FM (Fe)/AFM (FeO_x)/wFM (Fe₂O₃), whilst the spin directions lie in the sample plane for all the samples. The self-stabilized intermediate oxide can act as a physical barrier for spins to be injected into the wFM oxide, implying a substantial influence on tailoring the spin tunneling efficiency for spintronics application.