title: Magnetic interactions in cubic-, hexagonal- and trigonal-barium iron oxide fluoride, BaFeO2F.
abstract: (57)Fe Mössbauer spectra have been recorded from the hexagonal (6H)- and trigonal (15R)- modifications of BaFeO2F and are compared with those previously recorded from the cubic form of BaFeO2F. The spectra, recorded over a temperature range from 15 to 650 K show that all of the iron in all the compounds is in the Fe(3+) state. Spectra from the 6H- and 15R-modifications were successfully fitted with components that were related to the Fe(1) and Fe(2) structural sites in the 6H variant and to the Fe(1), Fe(2) and Fe(3) structural sites in the 15R form. The magnetic ordering temperatures were determined as 597  ±  3 K for 6H-BaFeO2F and 636  ±  3 K for 15R-BaFeO2F. These values are surprisingly close to the value of 645  ±  5 K determined for the cubic form. The magnetic interactions in the three forms are compared with a view to explaining this similarity of magnetic ordering temperature.
authors.affiliation: School of Chemistry, The University of Birmingham, Birmingham B15 2TT, UK. Technical University of Darmstadt, Joint Research Laboratory Nanomaterials, Jovanka-Bontschits-Straße 2, 64287 Darmstadt, Germany. Karlsruhe Institute of Technology, Institute of Nanotechnology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Clemens
authors.forename: José F
authors.initials: JF
authors.lastname: Marco
authors.forename: Michael F
authors.initials: MF
authors.lastname: Thomas
authors.forename: Susan D
authors.initials: SD
authors.lastname: Forder
authors.forename: Hongbin
authors.initials: H
authors.lastname: Zhang
authors.forename: Simon
authors.initials: S
authors.lastname: Cartenet
authors.forename: Anais
authors.initials: A
authors.lastname: Monze
authors.forename: Paul A
authors.initials: PA
authors.lastname: Bingham
authors.forename: Peter R
authors.initials: PR
authors.lastname: Slater
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Berry