Original close-packed structure and magnetic properties of the Pb4Mn9O20 manganite |
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| Authors: | Artem M Abakumov Joke Hadermann Alexander A Tsirlin Haiyan Tan Jo Verbeeck Haitao Zhang Evgeny V Dikarev Roman V Shpanchenko Evgeny V Antipov |
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| Institution: | aEMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium;bDepartment of Chemistry, Moscow State University, 119992 Moscow, Russia;cMax Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany;dDepartment of Chemistry, University at Albany, SUNY, 1400 Washington Avenue CHM 315 Albany, NY 12222, USA |
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| Abstract: | The crystal structure of the Pb4Mn9O20 compound (previously known as “Pb0.43MnO2.18”) was solved from powder X-ray diffraction, electron diffraction, and high resolution electron microscopy data (S.G. Pnma, a=13.8888(2) Å, b=11.2665(2) Å, c=9.9867(1) Å, RI=0.016, RP=0.047). The structure is based on a 6H (cch)2 close packing of pure oxygen “h”-type (O16) layers alternating with mixed “c”-type (Pb4O12) layers. The Mn atoms occupy octahedral interstices formed by the oxygen atoms of the close-packed layers. The MnO6 octahedra share edges within the layers, whereas the octahedra in neighboring layers are linked through corner sharing. The relationship with the closely related Pb3Mn7O15 structure is discussed. Magnetization measurements reveal a peculiar magnetic behavior with a phase transition at 52 K, a small net magnetization below the transition temperature, and a tendency towards spin freezing. |
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| Keywords: | Lead manganese oxide Close packing Crystal structure Magnetic properties Transmission electron microscopy EELS |
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