From the modern scientific landscape of nanotechnology research, the manipulation of elements and compounds on a near-atomic scale has contributed to innovations, some of which affect our everyday life. The growth of thin films and multilayers has allowed systematic studies of reduced dimensionality and the electronic interplay between dissimilar materials. Important applications have emerged, notably the GMR effect1. However, such studies of systems containing actinide elements are, to our knowledge, absent, but offer exciting possibilities because of potential hybridization involving the 5f electronic states.

 

The samples are prepared by a dedicated sputtering facility at Oxford University, UK2.

  

Our investigation into uranium multilayers, which involves both bulk as well as element specific techniques, compares the structural properties2 and electronic interactions3,4,5 of uranium interleaved with layers of ferromagnetic Fe, Co, Ni, and Gd. Only in the case of U/Fe is a large magnetic moment induced on the U atoms, close to the interface5.

 

The study of epitaxial uranium films is initially concerned with the nature of the structural constraints incurred by the substrate and buffer6 and the potential for stabilizing structures otherwise absent in the bulk. a–U (which is the normal ambient orthorhombic phase) grows well on a Nb buffer on sapphire. In the bulk it exhibits a charge-density wave (CDW) at 43 K, so in epitaxial films an interesting question is the minimum thickness for the CDW to appear; we have already observed the CDW down to 10 nm. Using epitaxial hcp–Gd as a buffer, we have produced hcp–U for the first time7. The observed c/a = 1.90 is larger than for any other hexagonal element. We report also our first efforts to prepare epitaxial UO2 films.