Observation of Metal-Insulator Transition in Hollandite Vanadate, K_2V_8O_<16>

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Author(s)

    • YAMAURA Jun-Ichi
    • Materials Design and Characterization Laboratory, Institute for Solid State Physics, University of Tokyo
    • YAMAUCHI Touru
    • Materials Design and Characterization Laboratory, Institute for Solid State Physics, University of Tokyo
    • UEDA Hiroaki
    • Materials Design and Characterization Laboratory, Institute for Solid State Physics, University of Tokyo
    • GOTOU Hirotada
    • Division of New Materials Science, Institute for Solid State Physics, University of Tokyo
    • YAGI Takehiko
    • Division of New Materials Science, Institute for Solid State Physics, University of Tokyo
    • UEDA Yutaka
    • Materials Design and Characterization Laboratory, Institute for Solid State Physics, University of Tokyo

Abstract

We have synthesized hollandite vanadate, K<SUB>2</SUB>V<SUB>8</SUB>O<SUB>16</SUB>, by a solid-state reaction under 4 GPa at 1473 K for one hour, and investigated its structural and electromagnetic properties. We found a metal–insulator transition with a two-step jump of resistivity of about three orders at around 170 K. The magnetic susceptibility is reduced to a small value at the transition, suggesting the formation of V<SUP>4+</SUP>–V<SUP>4+</SUP> singlet pairs and V<SUP>3+</SUP>–V<SUP>3+</SUP> pairs in the low-temperature insulator phase. The transition is of first order accompanied by a structural change from a tetragonal to a monoclinic structure. The low-temperature phase has a superlattice of \\sqrt2<I>a</I>×\\sqrt2<I>a</I>×2<I>c</I>, where <I>a</I> and <I>c</I> denote the parameters of the primitive cell for the simple tetragonal hollandite structure, suggesting a charge ordering of V<SUP>4+</SUP> and V<SUP>3+</SUP>. We construct a possible charge order model from the obtained results, in which two kinds of double-chain formed by V<SUP>3+</SUP> and V<SUP>4+</SUP> chains and by single V<SUP>4+</SUP> chains order in a manner that gives a superlattice of \\sqrt2×\\sqrt2 in the <I>a</I>–<I>b</I> plane. The V<SUP>4+</SUP>–V<SUP>4+</SUP> and V<SUP>3+</SUP>–V<SUP>3+</SUP> pairs are formed in each chain along the <I>c</I>-axis, resulting in a duplication of the <I>c</I>-axis.

Journal

  • Journal of the Physical Society of Japan

    Journal of the Physical Society of Japan 75(7), "73801-1"-"73801-4", 2006-07-15

    The Physical Society of Japan (JPS)

References:  36

Codes

  • NII Article ID (NAID)
    110004777966
  • NII NACSIS-CAT ID (NCID)
    AA00704814
  • Text Lang
    ENG
  • Article Type
    SHO
  • ISSN
    00319015
  • NDL Article ID
    7973732
  • NDL Source Classification
    ZM35(科学技術--物理学)
  • NDL Call No.
    Z53-A404
  • Data Source
    CJP  NDL  NII-ELS  J-STAGE 
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