Fermi surface study of pseudomorphic Fe1-xNix and Co1-xNix thin films on Cu(100)

We report angle resolved photoemission studies of the electronic behavior o f ultrathin epitaxial layers of fcc structured binary alloys, Fe1-xNix and Co1-xNix, deposited by molecular beam epitaxy on Cu(100) substrates. In par ticular, we have used Fermi surface mapping to monitor changes in the Fermi surface with increasing magnetization density. Fe1-xNix and Co1-xNix binar y alloys show a different behavior in the bulk. Co1-xNix is structurally an d magnetically well-behaved. In particular, the magnetic moment varies line arly as a function of concentration. This is in sharp contrast to fcc Fe1-x Nix which displays a magnetic instability at similar to 65% Fe content. An, extended regime of fcc stability is possible via epitaxy on Cu(100). The c hanges in the Fermi surfaces of Fe1-xNix and Co1-xNix pseudomorphic film al loys depending on various concentrations of Ni have been investigated in a large photon energy regime. We address the following question: To what degr ee is the Fermi surface sharply preserved in substitutional alloys? (C) 199 9 American Vacuum Society. [S0734-2101(99)01004-0].