title: Study of the valence state and electronic structure in Sr(2)FeMO(6) (M = W, Mo, Re and Sb) double perovskites.
abstract: The knowledge of the oxidation state of the transition metal cations in Sr(2)FeMO(6) (M = W, Mo, Re and Sb) double perovskites is of paramount importance to understand their appealing magnetoresistive or magnetic properties. We present a systematic investigation of the valences of Fe, W, Mo, Re and Sb cations in these perovskites using three different and complementary techniques of analysis. We have used a diffraction method, neutron powder diffraction (NPD), coupled with the bond-valence model; and two spectroscopy methods, X-ray photoemission spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). These two techniques are also complementary since XPS analyses the surface of the samples whereas XAS probes the bulk material. The analysis of the Fe K-edge spectra of the four samples shows a clear shift of the Fe K-edge as the valence of iron increases in the sequence M = W, Mo, Re and Sb. In addition, XANES pre-edge structures unveil a progressive reduction in the occupancy level of the Fe-3d band as the oxidation state of iron increases along the sequence M = W, Mo, Re and Sb. Finally, XANES computations have determined the electronic structures of Sr(2)FeWO(6), Sr(2)FeMoO(6), Sr(2)FeReO(6) and Sr(2)FeSbO(6).
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco, E-28049 Madrid, España. mretuerto@icmm.csic.es
authors.forename: M
authors.initials: M
authors.lastname: Retuerto
authors.forename: F
authors.initials: F
authors.lastname: Jiménez-Villacorta
authors.forename: M J
authors.initials: MJ
authors.lastname: Martínez-Lope
authors.forename: Y
authors.initials: Y
authors.lastname: Huttel
authors.forename: E
authors.initials: E
authors.lastname: Roman
authors.forename: M T
authors.initials: MT
authors.lastname: Fernández-Díaz
authors.forename: J A
authors.initials: JA
authors.lastname: Alonso