First-principles investigation of magnetism of U films and U(001)(1)/Fe(110)(3) multilayers.

The magnetism of surfaces and interfaces can differ strongly from the magnetism of corresponding bulk materials. In the case of actinide systems the study of the surfaces and interfaces is still at the very beginning. In this work, we investigated the electronic and magnetic properties of U films and U(001)(1)/Fe(110)(3) multilayers within the framework of the density functional theory. We report both scalar-relativistic and fully relativistic calculations. The exchange correlation potential was treated in the generalized gradient approximation (GGA). In agreement with previous calculation by Stojic et al (2003 Phys. Rev. B 68 094407) we obtained the surface layer of the U films to be magnetic for the bulk lattice parameter. The dependence of the magnetic properties of the U films on the lattice parameter was studied. It is shown that decreasing distances between U atoms lead to decreasing magnetic moment and finally to the nonmagnetic ground state. The variation of the magnetic moment as a function of the lattice parameter is discontinuous. Using the frozen-magnon approach we evaluated the parameters of the inter-atomic exchange interactions and estimated the Curie temperature. The calculation for U(001)(1)/Fe(110)(3) multilayers showed that the U layer is magnetic with the direction of the U moments opposite to the Fe moments. The importance of the U-Fe hybridization is revealed. Both the intra-layer (U-U, Fe-Fe) and inter-layer (U-Fe) exchange interactions were evaluated. The temperature dependence of the layer magnetizations was studied within the random-phase approximation for the Heisenberg Hamiltonian for classical spins.