title: First-order transition between a small gap semiconductor and a ferromagnetic metal in the isoelectronic alloy FeSi1-xGex.
abstract: The contrasting ground states of isoelectronic, isostructural FeSi and FeGe are explained within an extended local density approximation scheme (LDA+U) by an appropriate choice of the Coulomb repulsion U on the Fe sites. A minimal two-band model with interband interactions leads to a phase diagram for the alloys FeSi1-xGex. A mean field approximation gives a first-order transition between a small gap semiconductor and a ferromagnetic metal as a function of magnetic field, temperature, and concentration x. Unusually the transition from metal to insulator is driven by broadening, not narrowing, the bands and it is the metallic state that shows magnetic order.
authors.affiliation: Institute for Theoretical Physics, ETH Hönggerberg, CH-8093 Zürich, Switzerland.
authors.forename: V I
authors.initials: VI
authors.lastname: Anisimov
authors.forename: R
authors.initials: R
authors.lastname: Hlubina
authors.forename: M A
authors.initials: MA
authors.lastname: Korotin
authors.forename: V V
authors.initials: VV
authors.lastname: Mazurenko
authors.forename: T M
authors.initials: TM
authors.lastname: Rice
authors.forename: A O
authors.initials: AO
authors.lastname: Shorikov
authors.forename: M
authors.initials: M
authors.lastname: Sigrist