Magnetism of U/Fe multilayers

Abstract Magnetic multilayers are known to have behaviour shaped by the intrinsic magnetic properties of their constituents and of their interactions. Multilayers composed of Uranium (5f electrons) and transition metal (3d electrons) provide the unique combination of a potentially large orbital moment with strong electronic hybridisation effects between the extended 5f states and the strongly magnetic 3d states. In this study U/Fe multilayers with layer thicknesses 20 A U  A and 30 A Fe  A were fabricated by dc sputtering in a UHV chamber. X-ray reflectivity (XRR) spectra show good layer structure with little interdiffusion at interfaces. We have investigated the magnetic moment profile normal to the layers by polarised neutron reflectivity (PNR) and specifically whether magnetic moments are induced on the uranium layers by the proximity of the iron layers. The PNR results show a magnetic moment on the iron layers reduced from that of pure bcc iron and they set an upper limit on any moment on the U layers. A more sensitive search for the U moment has involved resonant X-ray magnetic reflectivity measurements at energies around the UM IV edge using different geometries of circular polarisation helicity and applied magnetic field. Some evidence of U moments has been observed.