SPIN POLARIZATION OF VANADIUM OVERLAYERS ON A SEMIINFINITE TANTALUM SUBSTRATE

We investigate the substrate bandwidth effect on the onset of magnetis m in V overlayers. The local magnetic moments and magnetic order at th e V/Ta interface of ultrathin V films is studied. Different crystallog raphic directions (001),(011) and (111) have been considered. The magn etism is described within a real-space tight-binding approach ill the unrestricted Hartree-Fock approximation of the Hubbard Hamiltonian. Th e density of states has been calculated within the recursion technique . The onset of. magnetism depends strongly on the faces considered. Ma gnetism is more pronounced for the (001) surface and is found to decre ase when V is allowed to relax in order to recover its bulk volume. Th e magnetic moments of the surface layers are strongly enhanced by addi tion of more V layers. A sizeable induced moment appears in the Ta int erface layer which decreases by addition of more V layers. The same be havior is shown to occur in the Nb substrate but it is more pronounced as compared to that of Ta. This behavior is expected since the bandwi dth of Nb is smaller than that of Ta and their lattice parameters are approximately the same. (C) 1997 Elsevier Science B.V.