title: Structural transition at 360 K in the CaFe₅O₇ ferrite: toward a new charge ordering distribution.
abstract: An efficient synthesis route is proposed to obtain single phase powder ceramic of CaFe5O7. This complex structure can be described as an intergrowth between one CaFe2O4 unit and n = 3 slices of FeO Wüstite-type structure. A detailed structural study has been carried out at room temperature combining transmission electron microscopy (TEM) observations (ED, HREM), scanning transmission electron microscopy (STEM-HAADF), and X-ray diffraction data. The analysis of these data has revealed an unexpected supercell with a monoclinic symmetry. From the hkl conditions deduced from the electron diffraction study and the analysis of X-ray diffraction data by simulated annealing, a structural model considering the centrosymmetric P2₁/m setting can be proposed. In addition the first magnetic and electrical transport measurements are reported showing a sharp peak in magnetic susceptibility and a strong localization around 360 K, associated to a structural change from monoclinic setting to orthorhombic one.
authors.affiliation: Laboratoire CRISMAT ENSICAEN UMR CNRS 6508 , 6 Boulevard du Maréchal Juin, 14050 Caen Cedex 04, France.
authors.forename: C
authors.initials: C
authors.lastname: Delacotte
authors.forename: F
authors.initials: F
authors.lastname: Hüe
authors.forename: Y
authors.initials: Y
authors.lastname: Bréard
authors.forename: S
authors.initials: S
authors.lastname: Hébert
authors.forename: O
authors.initials: O
authors.lastname: Pérez
authors.forename: V
authors.initials: V
authors.lastname: Caignaert
authors.forename: J M
authors.initials: JM
authors.lastname: Greneche
authors.forename: D
authors.initials: D
authors.lastname: Pelloquin