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Introducing a Large Polar Tetragonal Distortion into Ba-Doped BiFeO3 by Low-Temperature Fluorination

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posted on 01.12.2014, 00:00 by Oliver Clemens, Robert Kruk, Eric A. Patterson, Christoph Loho, Christian Reitz, Adrian J. Wright, Kevin S. Knight, Horst Hahn, Peter R. Slater
This article reports on the synthesis and crystallographic and magnetic structure of barium-doped BiFeO3 compounds with approximate composition Bi1–xBaxFeO3–x/2, as well as those of the fluorinated compounds Bi1–xBaxFeO3–xFx (both with x = 0.2, 0.3), prepared by low-temperature fluorination of the oxide precursors using polyvinylidenedifluoride. Whereas the oxide compounds were obtained as cubic (x = 0.2) and slightly tetragonal (x = 0.3, c/a ≈ 1.003) distorted perovskite compounds, a large tetragonal polar distortion was observed for the oxyfluoride compounds (c/a ≈ 1.08 for x = 0.2 and ∼1.05 for x = 0.3), being isostructural to tetragonal PbTiO3. Although described differently in previous reports on Ba-doped BiFeO3, the observed remanent magnetization is found to agree well with the amount of BaFe12O19 only detectable by neutron diffraction and the well-known magnetic properties of BaFe12O19. The oxyfluoride compounds show G-type antiferromagnetic ordering with magnetic moments lying in the a/b plane.