U/Fe Multilayers

Some of the properties exhibited by Ce in multilayers can be expected in samples incorportating the Actinides, by using uranium. Uranium has some very interesting and potentially useful magnetic properties. Uranium can possess very large orbital magnetic moments which, through their coupling to the lattice, produce substantial magnetic anisotropy. This may allow perpendicular magnetic anisotropy, an important goal in magneto-optical devices. Also of interest for magneto-optical applications is the Kerr-effect, also of a large magnitude in some uranium compounds.

Similar to the $ 4f$ electrons in cerium, uranium $ 5f$ electrons have a large spatial extent and can potentially hybridise with $ 3d$ electrons. These can produce polarisation effects across the multilayer interfaces, potentially of greater magnitude than in Ce/Fe multilayers.

In its elemental form uranium is not magnetic. When in close proximity the itinerant $ 5f$ electrons form wide bands through $ f$-$ d$ hybridisation, producing no localised magnetic moment.[44] To attain a magnetically ordered state the uranium atoms must be forced sufficiently apart to reduce the formation of $ 5f$ bands. Although unlikely to occur within the uranium layers of the U/Fe multilayer, interface effects such as strain or interdiffusion of elements may produce magnetic uranium atoms within the immediate presence of the U/Fe interface.

Dr John Bland, 15/03/2003