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Metal-insulator transition near the superconducting phase of two-dimensional cobalt oxides

Research Project

Project/Area Number 17540323
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Condensed matter physics II
Research InstitutionNagoya University

Principal Investigator

KOBAYASHI Yoshiaki  Nagoya University, Division of Material Science, Associated Professor, 大学院理学研究科, 助教授 (60262846)

Co-Investigator(Kenkyū-buntansha) SATO Masatoshi  Nagoya University Division of Material Science, Professor, 大学院理学研究科, 教授 (40092225)
YASUI Yukio  Nagoya University, Division of Material Science, Assistant Professor, 大学院理学研究科, 助手 (80345850)
Project Period (FY) 2005 – 2006
Project Status Completed (Fiscal Year 2006)
Budget Amount *help
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2006: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2005: ¥1,900,000 (Direct Cost: ¥1,900,000)
KeywordsNa_xC0O_2・yH_2O / NMR Knight shift / nuclear electric quadrupole resonance / Cooper pairs / singlet / Na_<0.5>CoO_2 / neutron scattering / charge ordering / Na_xCoO_2・yH_2O / Na_<0.3>CoO_2・1.3H_2O / ナイトシフト / T_cへの不純物効果 / 反強磁性 / 中性子回折
Research Abstract

We have produced principally three results, which are of considering importance to the mechanism of the formation of the Cooper pairs in Na_xCoO_2・yH_2O superconductors.
(1) We have revealed that the superconducting pairs in the superconducting state of Na_xCoO_2・yH_2O are in the spin-singlet state, by the measurements of the ^<59>Co-NMR Knight shift for both magnetic field (H) directions parallel and perpendicular to the CoO_2planes in the superconducting state using single phase single crystals.
(2) The superconducting transition temperatures T_c of Na_xCoO_2・yH_2O have been found to exhibit the systematic dependence on the ^<59>Co nuclear electric quadrupole resonance frequency ν_Q. In the T-3ν_Q phase diagram, the superconducting region of 3ν_Q, spreading over the region between 〜12.0 and 〜12.9 MHz, is divided into two regions by the non-superconducting phase between 〜12.5 and 〜12.6 MHz.
We have investigated the origin of the non-superconducting phase by detailed experimental measurem … More ents of ^<59>Co-NQR and ^2D-NMR and found that the non-superconducting phase is in the charge-density-wave (CDW) or the charge disproportionate state, in which the magnetic moments induced inhomogeneously by this transition become frozen at low temperatures.
(3) We have revealed that the x dependence of the electronic nature of Na_x,CoO_2 which is the parent compound of Na_<0.3>CoO_2・1.3H_2O superconductors. In particular, the successive phase transitions observed in Na_<0.5>CoO_2 at 87 K (T_<c1>) and 53 K (T_<c2>) have been studies. Na_<0.5>CoO_2 indicates the antiferromagnetic ordering below T_<c1>, where we have determined the unusual magnetic structure by ^<59>Co-NMR and neutron diffraction studies.
It has been found from the X dependence of χ-T and 1/T_1-T curves that the two-dimensional nature of the electrons of Na_xCoO_2 is enhanced and the antiferromagnetic correlation increases in this system as the Na concentration x decreases. Therefore, the superconducting pairs are expected to be in the singlet state. This is consistent with the results of the Knight shift studies in Na_<0.3>CoO_2-1.3H_2O. Less

Report

(3 results)
  • 2006 Annual Research Report   Final Research Report Summary
  • 2005 Annual Research Report
  • Research Products

    (34 results)

All 2007 2006 2005

All Journal Article (34 results)

  • [Journal Article] Observation of the in-plane ordering D_2O molecules in Na_xCoO_2-yD_2O by neutron diffraction2007

    • Author(s)
      T.Moyoshi, Y.Yasui, M.Soda, Y.Kobayashi, M.Sato, K.Kakurai
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol. 310 Issue 2, Part 1

      Pages: 654-656

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] NMR and neutron scattering studies on Na_xCoO_2-yH_2O2007

    • Author(s)
      M.Sato, Y.Kobayashi, T.Moyoshi, M.Yokoi, H.Watanabe, Y.Mori, K.Kakurai
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol.310 Issue 2, Part 1

      Pages: 666-668

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Studies of successive transition in K_<0.5>CoO_22007

    • Author(s)
      M.Yokoi, Y.Mori, T.Moyoshi, Y.Kobayashi, M.Sato
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol.310 Issue 2, Part 1

      Pages: 672-674

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] NMR Studies of successive transition in Na_<O.5>CoO_22007

    • Author(s)
      Y.Kobayashi, M.Yokoi, T.Moyoshi, H.Watanabe, M.Sato
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol.310 Issue 2, Part 1

      Pages: 675-677

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Observation of the in-plane ordering D2O molecules in Na_xCoO_2・yD_2O by neutron diffraction.2007

    • Author(s)
      T.Moyoshi, Y.Yasui, M.Soda, Y.Kobayashi, M.Sato, K.Kakurai
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol.310, issue 2, Part 1

      Pages: 654-656

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] NMR and neutron scattering studies on Na_xCoO_2・yH_2O2007

    • Author(s)
      M.Sato, Y.Kobayashi, T.Moyoshi, M.Yokoi, H.Watanabe, Y.Mori, K.Kakurai
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol.310, issue 2, Part 1

      Pages: 666-668

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Studies of successive transition in K_<0.5>CoO_22007

    • Author(s)
      M.Yokoi, Y.Mori, T.Moyoshi, Y.Kobayashi, M.Sato
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol.310, issue 2, Part 1

      Pages: 672-674

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] NMR Studies of successive transition in Na_<0.5>CoO_22007

    • Author(s)
      Y.Kobayashi, M.Yokoi, T.Moyoshi, H.Watanabe, M.Sato
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol.310, issue 2, Part 1

      Pages: 675-677

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Observation of the in-plane ordering of D_2O molecules in Na_xCoO_<2・y>D_2O by neutron diffraction2007

    • Author(s)
      T.Moyoshi, Y.Yasui, M.Soda, Y.Kobayashi, M.Sato, K.Kakurai
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol. 310 Issue 2, Part 1

      Pages: 654-656

    • Related Report
      2006 Annual Research Report
  • [Journal Article] NMR and neutron scattering studies on Na_xCoO_<2・y>H_2O2007

    • Author(s)
      M.Sato, Y.Kobayashi, T.Moyoshi, M.Yokoi, H.Watanabe, Y.Mori, K.Kakurai
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol. 310 Issue 2, Part 1

      Pages: 666-668

    • Related Report
      2006 Annual Research Report
  • [Journal Article] Studies of successive transitions in K_<0.5>CoO_22007

    • Author(s)
      M.Yokoi, Y.Mori, T.Moyoshi, Y.Kobayashi, M.Sato
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol. 310 Issue 2, Part 1

      Pages: 672-674

    • Related Report
      2006 Annual Research Report
  • [Journal Article] NMR studies of successive transitions in Na_<0.5>CoO_22007

    • Author(s)
      Y.Kobayashi, M.Yokoi, T.Moyoshi, H.Watanabe, M.Sato
    • Journal Title

      Journal of Magnetism and Magnetic Materials Vol. 310 Issue 2, Part 1

      Pages: 675-677

    • Related Report
      2006 Annual Research Report
  • [Journal Article] Magnetic and Metal-Insulator Transitions in β-Na_<0.5>CoO_2 and γ-Na_<0.5>CoO_2-NMR and Neutron Diffraction Studies-2006

    • Author(s)
      H.Watanabe, Y.Mori, M.Yokoi, T.Moyoshi, M.Soda, Y.Yasui, Y.Kobayashi, M.Sato, N.Igawa, K.Kakurai
    • Journal Title

      Journal of the Physical Society of Japan Vol.75 No.3

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Search for Magnetic Excitation Spectra of Na_xCoO_2-yD_2O -Neutron Scattering-2006

    • Author(s)
      T.Moyoshi, Y.Yasui, M.Soda, Y.Kobayashi, M.Sato, K.Kakurai
    • Journal Title

      Journal of the Physical Society of Japan Vol.75 No.7

    • NAID

      110004777980

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Magnetic Properties of Superconducting Cobalt Oxides Na_xCoO_2-yH_2O2006

    • Author(s)
      Y.Kobayashi, T.Moyoshi, H.Watanabe, M.Yokoi, M.Sato
    • Journal Title

      Journal of the Physical Society of Japan Vol.75 No.7

    • NAID

      110004777992

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Existence of Co^<3+> Low-Spin State in TbBaCo_2O_<5.5>2006

    • Author(s)
      M.Soda, Y.Yasui, Y.Kobayashi, T.Fujita, M.Sato, K.Kakurai
    • Journal Title

      Journal of the Physical Society of Japan Vol.75 No.10

    • NAID

      110004821521

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Magnetic and Metal-Insulator Transitions in β-Na_<0.5>CoO_2 and γ-Na_<0.5>CoO_2 -NMR and Neutron Diffraction Studies-2006

    • Author(s)
      H.Watanabe, Y.Mori, M.Yokoi, T.Moyoshi, M.Soda, Y.Yasui, Y.Kobayashi, M.Sato, N.Igawa, K.Kakurai
    • Journal Title

      Journal of the Physical Society of Japan Vol.75, No.3

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Search for Magnetic Excitation Spectra of Na_xCoO_2・yD_2O -Neutron Scattering-2006

    • Author(s)
      T.Moyoshi, Y.Yasui, M.Soda, Y.Kobayashi, M.Sato, K.Kakurai
    • Journal Title

      Journal of the Physical Society of Japan Vol.75, No.7

    • NAID

      110004777980

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Magnetic Properties of Superconducting Cobalt Oxides Na_xCoO_2・yH_2O2006

    • Author(s)
      Y.Kobayashi, T.Moyoshi, H.Watanabe, M.Yokoi, M.Sato
    • Journal Title

      Journal of the Physical Society of Japan Vol.75, No.7

    • NAID

      110004777992

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Existence of Co^<3+> Low-Spin State in TbBaCo_2O_<5.5>2006

    • Author(s)
      M.Soda, Y.Yasui, Y.Kobayashi, T.Fujita, M.Sato, K.Kakurai
    • Journal Title

      Journal of the Physical Society of Japan Vol.75, No.10

    • NAID

      110004821521

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Search for Magnetic Excitation Spectra of Na_xCoO_<2・y>D_2O -Neutron Scattering-2006

    • Author(s)
      T.Moyoshi, Y.Yasui, M.Soda, Y.Kobayashi, M.Sato, K.Kakurai
    • Journal Title

      Journal of the Physical Society of Japan Vol. 75 No. 7

    • NAID

      110004777980

    • Related Report
      2006 Annual Research Report
  • [Journal Article] Magnetic Properties of Superconducting Cobalt Oxides Na_xCoO_<2・y>H_2O2006

    • Author(s)
      Y.Kobayashi, T.Moyoshi, H.Watanabe, M.Yokoi, M.Sato
    • Journal Title

      Journal of the Physical Society of Japan Vol. 75 No. 7

    • NAID

      110004777992

    • Related Report
      2006 Annual Research Report
  • [Journal Article] Magnetic and Metal-Insulator Transition in β-Na_<0.5>CoO_2 and γ-Na_<0.5>CoO_2 -NMR and Neutron Diffraction Studies-2006

    • Author(s)
      H.Watanabe, Y.Mori, T.Moyoshi, M.Soda, Y.Yasui, Y.Kobayashi, M.Sato, N.Igaewa, K.Kakurai
    • Journal Title

      Journal of Physical Society of Japan Vol.75,No.3

    • Related Report
      2005 Annual Research Report
  • [Journal Article] ^<59>Co-NMR Knight shift of aligned crystals and polycrystalline samples of Superconducting Na_xCoO_2-yH_2O2005

    • Author(s)
      Y.Kobayashi, H.Watanabe, M.Yokoi, T.Moyoshi, M.Sato
    • Journal Title

      Journal of the Physical Society of Japan Vol.74 No.6

      Pages: 1800-1805

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] ^<59>Co-NMR Knight shift of Superconducting Three-Layer Na_xCoO_2-yH_2O2005

    • Author(s)
      H.Watanabe, Y.Kobayashi, M.Sato
    • Journal Title

      Journal of the Physical Society of Japan Vol.74 No.9

      Pages: 2563-2567

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Magnetic Correlation of Na_xCoO_2 and Successive Phase Transitions of Na_<0.5>CoO_2-NMR and Neutron Diffraction Studies-2005

    • Author(s)
      M.Yokoi, T.Moyoshi, Y.Kobayashi, M.Soda, Y.Yasui, M.Sato, K.Kakurai
    • Journal Title

      Journal of the Physical Society of Japan Vol.74 No.11

      Pages: 3046-3056

    • NAID

      110002325544

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] ^<59>Co-NMR Knight shift of aligned crystals and polycrystalline samples of Superconducting Na_xCo_O2・yH_2O2005

    • Author(s)
      Y.Kobayashi, H.Watanabe, M.Yokoi, T.Moyoshi, M.Sato
    • Journal Title

      Journal of the Physical Society of Japan Vol.74, No.6

      Pages: 1800-1805

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] ^<59>Co-NMR Knight shift of Superconducting Three-Layer Na_xCoO_2・yH_2O2005

    • Author(s)
      H.Watanabe, Y.Kobayashi, M.Sato
    • Journal Title

      Journal of the Physical Society of Japan Vol.74, No. 9

      Pages: 2563-2567

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Magnetic Correlation of Na_xCoO_2 and Successive Phase Transitions of Na_<0.5>CoO_2 -NMR and Neutron Diffraction Studies-2005

    • Author(s)
      M.Yokoi, T.Moyoshi, Y.Kobayashi, M.Soda, Y.Yasui, M.Sato, K.Kakurai
    • Journal Title

      Journal of the Physical Society of Japan Vol.74, No.11

      Pages: 3046-3056

    • NAID

      110002325544

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Magnetic Correlation of Na_xCoO_2 and Successive Phase Transitions of Na_<0.5>CoO_2 -NMR and Neutron Diffraction Studies-2005

    • Author(s)
      M.Yokoi, T.Moyoshi, Y.Kobayashi, M.Soda, Y.Yasui, K.Kakurai
    • Journal Title

      Journal of the Physical Society of Japan Vol.74,No.11

      Pages: 3046-3056

    • NAID

      110002325544

    • Related Report
      2005 Annual Research Report
  • [Journal Article] ^<59>Co-NMR Knight shift of superconducting Three-Layer Na_xCoO_2・yH_2O2005

    • Author(s)
      H.Watanabe, Y.Kobayashi, M.Sato
    • Journal Title

      Journal of the Physical Society of Japan Vol.74,No.9

      Pages: 2563-2567

    • Related Report
      2005 Annual Research Report
  • [Journal Article] On the Mechanism of the Spin State Transition2005

    • Author(s)
      T.Fujita, S.Kawabata, M.Sato, N.Kurita, M.Hedo, Y.Uwatoko
    • Journal Title

      Journal of the Physical Society of Japan Vol.74,No.8

      Pages: 2294-2300

    • Related Report
      2005 Annual Research Report
  • [Journal Article] ^<59>Co-NMR Knight shift of aligned crystals and polycrystalline samples of superconducting Na_xCoO_2・yH_2O2005

    • Author(s)
      Y.Kobayashi, H.Watanabe, M.Yokoi, T.Moyoshi, M.Sato
    • Journal Title

      Journal of the Physical Society of Japan Vol.74,No.6

      Pages: 1800-1805

    • Related Report
      2005 Annual Research Report
  • [Journal Article] Magnetic and Charge Ordering Transitions of PrBaCo_2O_52005

    • Author(s)
      M.Soda, Y.Yasui, M.Sato, K.Kakurai
    • Journal Title

      Journal of the Physical Society of Japan Vol.74,No.6

      Pages: 1875-1876

    • NAID

      110001979628

    • Related Report
      2005 Annual Research Report

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Published: 2005-04-01   Modified: 2020-05-15  

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