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Accueil du site > Vie du Laboratoire > Archives > Archives 2013 "A la Une" >

27 mai 2013

Impact of Mn3+ upon Structure and Magnetism of the Perovskite Derivative Pb2−xBaxFeMnO5 (x ∼ 0.7)

Based on the Mn3+ for Fe3+ substitution in Pb2-xBaxFe2O5, a novel oxide Pb1.3Ba0.7MnFeO5 has been synthesized at normal pressure. Though it belongs to the same structural family, the mixed “MnFe” oxide exhibits a very different structural distortion of its framework compared to the pure “Fe2” oxide, due to the Jahn-Teller effect of Mn3+. Combined neutron diffraction, high resolution electron microscopy/HAADF-STEM investigations allow the origin of this difference to be determined. Here we show that the MO6 octahedra of the double perovskite layers in the “MnFe” structure exhibit a strong tetragonal pyramidal distortion “5+1” whereas the “Fe2” structure shows a tetrahedral distortion “4+2” of the FeO6 octahedra. Similarly the MO5 polyhedra of the “MnFe” structure tend toward a tetragonal pyramid, whereas the FeO5 polyhedra of the “Fe2” structure are closer to a trigonal bipyramid. Differently from the oxide Pb2-xBaxFe2O5, which is antiferromagnetic, the oxide Pb1.3Ba0.7MnFeO5 exhibits a spin glass behavior with Tg = 50 K in agreement with the disordered distribution of the Mn3+ and Fe3+ species.

Authors : N. Barrier, O. I. Lebedev, Md. Motin Seikh, F. Porcher and B. Raveau.| Inorg. Chem. 2013, 52, 6073−6082