title: Three Oxidation States of Manganese in the Barium Hexaferrite BaFe12-xMnxO19.
abstract: The coexistence of three valence states of Mn ions, namely, +2, +3, and +4, in substituted magnetoplumbite-type BaFe12-xMnxO19was observed by soft X-ray absorption spectroscopy at the Mn-L2,3edge. We infer that the occurrence of multiple valence states of Mn situated in the pristine purely iron(III) compound BaFe12O19is made possible by the fact that the charge disproportionation of Mn3+into Mn2+and Mn4+requires less energy than that of Fe3+into Fe2+and Fe4+, related to the smaller effective Coulomb interaction of Mn3+(d4) compared to Fe3+(d5). The different chemical environments determine the location of the differently charged ions: with Mn3+occupying positions with (distorted) octahedral local symmetry, Mn4+ions prefer octahedrally coordinated sites in order to optimize their covalent bonding. Larger and more ionic bonded Mn2+ions with a spherical charge distribution accumulate at tetrahedrally coordinated sites. Simulations of the experimental Mn-L2,3XAS spectra of two different samples with x = 1.5 and x = 1.7 led to Mn2+:Mn3+:Mn4+atomic ratios of 0.16:0.51:0.33 and 0.19:0.57:0.24.
authors.affiliation: University of Stuttgart , Stuttgart 70049, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Nemrava
authors.affiliation: South Ural State University , Chelyabinsk 454080, Russia.
authors.forename: Denis A
authors.identifier: http://orcid.org/0000-0002-5190-9834
authors.initials: DA
authors.lastname: Vinnik
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids , Dresden 01187, Germany.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Hu
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids , Dresden 01187, Germany.
authors.forename: Martin
authors.identifier: http://orcid.org/0000-0001-7061-3492
authors.initials: M
authors.lastname: Valldor
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids , Dresden 01187, Germany.
authors.forename: Chang-Yang
authors.initials: CY
authors.lastname: Kuo
authors.affiliation: South Ural State University , Chelyabinsk 454080, Russia.
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Zherebtsov
authors.affiliation: South Ural State University , Chelyabinsk 454080, Russia.|Moscow Institute of Physics and Technology (State University) , Dolgoprudny, Moscow Region 141700, Russia.
authors.forename: Svetlana A
authors.initials: SA
authors.lastname: Gudkova
authors.affiliation: National Synchrotron Radiation Research Center , Hsinchu 30076, Taiwan.
authors.forename: Chien-Te
authors.initials: CT
authors.lastname: Chen
authors.affiliation: Max-Planck-Institute for Chemical Physics of Solids , Dresden 01187, Germany.
authors.forename: Liu Hao
authors.initials: LH
authors.lastname: Tjeng
authors.affiliation: University of Stuttgart , Stuttgart 70049, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Niewa