Observation of Structural Change in the Novel Ferromagnetic Metal-Insulator Transition of K sub( 2)Cr sub( 8)O sub( 16)

The synchrotron X-ray diffraction analysis of a single crystal of K ... Cr ... O ... has revealed a change from a tetragonal I 4/ m structure to a monoclinic P 112 ... / a (or P 112 ... / b ) structure across the metal-insulator transition at 95 K. In the low-temperature ferromagnetic insulator phas...

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Bibliographic Details
Published in:Journal of the Physical Society of Japan 2012-05, Vol.81 (5), p.1-1
Main Authors: Nakao, Akiko, Yamaki, Yuki, Nakao, Hironori, Murakami, Youichi, Hasegawa, Kunihiro, Isobe, Masahiko, Ueda, Yutaka
Format: Article
Language:English
Subjects:
Bonding
Charge
Chromium
Columns (structural)
Dimerization
Ferromagnetism
Lattices
Metal-insulator transition
Symbols
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Summary:The synchrotron X-ray diffraction analysis of a single crystal of K ... Cr ... O ... has revealed a change from a tetragonal I 4/ m structure to a monoclinic P 112 ... / a (or P 112 ... / b ) structure across the metal-insulator transition at 95 K. In the low-temperature ferromagnetic insulator phase, almost the same Cr-O bond lengths for the four Cr sites indicate no charge separation/order. However, characteristic displacements of the Cr and O sites, resulting in Cr-O bond alternations, are observed in a rectangular column formed by four CrO ... chains (four-chain column), which indicates the dimerization of the lattice with the formation of a Cr tetramer. There are two means of lattice dimerization. The spatial arrangement of the two types of four-chain columns with lattice dimerization is of neither the uniform type nor the checkerboard type but is of the stripe type. Such a stripe-type arrangement would result from the competition between lattice distortion and coulomb repulsion. (ProQuest: ... denotes formulae/symbols omitted.)
ISSN:0031-9015
1347-4073