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Title
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Topotactic reduction as a route to new close-packed anion deficient perovskites: structure and magnetism of
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Author
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Abstract
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| The anion-deficient perovskite 4H-BaMnO2+x has been obtained by a topotactic reduction, with LiH, of the hexagonal perovskite 4H-BaMnO3−x. The crystal structure of 4H-BaMnO2+x was solved using electron diffraction and X-ray powder diffraction and further refined using neutron powder diffraction (S.G. Pnma, a = 10.375(2) Å, b = 9.466(2) Å, c = 11.276(3) Å, at 373 K). The orthorhombic superstructure arises from the ordering of oxygen vacancies within a 4H (chch) stacking of close packed c-type BaO2.5 and h-type BaO1.5 layers. The ordering of the oxygen vacancies transforms the Mn2O9 units of face-sharing MnO6 octahedra into Mn2O7 (two corner-sharing tetrahedra) and Mn2O6 (two edge-sharing tetrahedra) groups. The Mn2O7 and Mn2O6 groups are linked by corner-sharing into a three-dimensional framework. The structures of the BaO2.5 and BaO1.5 layers are different from those observed previously in anion-deficient perovskites providing a new type of order pattern of oxygen atoms and vacancies in close packed structures. Magnetization measurements and neutron diffraction data reveal 4H-BaMnO2+x adopts an antiferromagnetically ordered state below TN ≈ 350 K. |
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Language
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English
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Source (journal)
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Journal of the American Chemical Society. - Washington, D.C., 1879, currens
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Publication
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Washington, D.C.
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American Chemical Society
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2009
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ISSN
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0002-7863
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DOI
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10.1021/JA903216D
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Volume/pages
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131
:30
(2009)
, p. 10598-10604
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ISI
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000268644400056
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Full text (Publisher's DOI)
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