2002 Fiscal Year Annual Research Report

新奇な量子流体の物質探索と相制御

Research Project

Project/Area Number	12046221
Research Institution	The University of Tokyo
Principal Investigator	高木英典東京大学, 大学院・新領域創成科学研究科, 教授 (40187935)
Co-Investigator(Kenkyū-buntansha)	廣井善二東京大学, 物性研究所, 助教授 (30192719) 上田寛東京大学, 物性研究所, 教授 (20127054)
Keywords	物質開拓 / 遷移金属酸化物 / 三次元フラストレーション系 / 量子磁性 / 超伝導 / 電荷秩序
Research Abstract	三次元フラストレーション系の舞台として、スピネル型酸化物、パイロクロ型酸化物の新物質・物性開拓が集中的に行われ、その結果を発信できたと考える。スピン1/2物質MgTi_2O_4の定比組成の試料を世界で初めて合成し、そこでパイエルス的金属-絶縁体転移を発見した。スピンヤーンテラー系CdCr_2O_4において、バルス強磁場下で1/2の磁化プラトーを発見し、AlV_2O_4の電荷秩序と同じ3-1型のスピン秩序が実現していることを明らかにした。この結果は3-1型の秩序がフラストレーションを解消する上で非常に普遍的であることを示している。パイロクロア酸化物超伝導体Cd_2Re_2O_7において、パイロクロア格子上の遍歴電子系が示す特異な構造と電子状態の不安定性について研究を行った。その結果、高対称なパイロクロア格子は2つの逐次構造相転移を示し、電子系の縮退を解くことによって安定化し、最後に歪んだ格子において超伝導を示すことが明らかになった。また、スピンアイス状態をとるパイロクロア酸化物Dy_2Ti_2O_7において磁場によるスピン次元性の制御を行い、新たにカゴメアイスと呼ばれるマクロに縮退した状態を見出した。フラストレーション系以外でも大きな研究の進展があった。電荷秩序を示すバナジウム酸化物Na_<0.33>V_2O_5において圧力誘起超伝導を発見した。バナジウム酸化物としてははじめての超伝導であるばかりか、電荷秩序と超伝導という観点からも意義が大きい。また新規金属秩序型マンガン酸化物を開発し、その電子相図の全貌を明らかにした。従来のペロフスカイト型マンガン酸化物には見られない、新しい電荷・軌道秩序や軌道・電荷・スビン自由度の分離などの現象を見出した

Research Products

(20 results)

All Other

All Publications (20 results)

[Publications] T.Nakajima, H.Kageyama, Y.Ueda: "Successive phase transitions in a metal-ordered manganite perovskite YBaMn_2O_4"J.Phys.Chem.Solids. 63. 913-916 (2002)
[Publications] Y.Ueda, M.Isobe, T.Yamauchi: "Superconductivity under high pressure in β(β')-vanadium bronzes"J.Phys.Chem.Solids. 63. 951-955 (2002)
[Publications] T.Yamauchi, Y.Ueda, N.Mori: "Pressure-Induced Superconductivity in β-Na_<0.33>V_2O_5 beyond Charge Ordering"Phys.Rev.Lett.. 89. 57002-1-57002-4 (2002)
[Publications] M.Isobe, Y.Ueda: "Observation of Phase Transition from Metal to Spin-Singlet Insulator in MgTi_2O_4 with S=1/2 Pyrochlore Lattice"J.Phys.Soc.Jpn.. 71. 1848-1851 (2002)
[Publications] T.Nakajima, Y.Ueda: "Structures and Electromagnetic Properties of New Metal-Ordered Manganite s : RBaMn_2O_6 (R=Y and Rare-Earth Elements)"J.Phys.Soc.Jpn.. 71. 2843-2846 (2002)
[Publications] Z.Hiroi, T.Yamauchi, T.Yamada, H.Hanawa, Y.Ohishi, O.Shinomura, H.Abliz, H.Hedo, Y.Uwatoko: "High-pressure study on the superconducting pyrochlore oxide Cd_2Re_2O_7"J.Phys.Chem.Solids. 71・6. 1553-1557 (2002)
[Publications] Z.Hiroi, J.Yamaura, Y.Muraoka, M.Hanawa: "Second phase transition in pyrochlore oxide Cd_2Re_2O_7"J.Phys.Soc.Jpn. 71・7. 1634-1636 (2002)
[Publications] Z.Hiroi, K.Matsuhira, S.Takagi, T.Tayaua, T.Sakakibara: "Specific heat of Kagome ice in the pyrochlore oxide Dy_2Ti_2O_7"J.Phys.Soc.Jpn. 72・2. 411-418 (2003)
[Publications] Ueda H, Nohara M, Kitazawa K, Takagi H, Fujinori A, Hizokawa T, Yagi T: "Copper pyrites CuS2 and CuSe2 as anion conductors"PHYSICAL REVIEW B. 65:(15). 115104 (2002)
[Publications] Hiroaki Ueda, Koichii Kitazawa, Hidenori Takagi, Takehiko Matsumoto: "Strong Carrier Concentration Dependence of Pressure Effect on Bipolaronic Transitions in Magneli Phase Ti_nO_<2n-1> (n=4,5,6)"J.Phys.Soc.Jpn. Vol.71,No.6. 1506-1510 (2002)
[Publications] C.Ulrich, S.Kondo, M.Reehuis, H.He, C.Bernhard, C.Niedermayer, F.Bouree, P.Bourges, M.Ohl, H.M.Ronnow, H.Takagi, B.Keimer: "Structural and magnetic instabilities of La_<2-x>Sr_xCaCu_2O_6"Phys.Rev.B. 65. 220507-1-220507-4 (2002)
[Publications] Lake B, Ronnow HM, Christensen NB, Aeppli G, Lefmann K, McMorrow DF, Vorderwisch P, Smeibidl P, Mangkorntong N, Sasagawa T, Nohara M, Takagi H, Mason TE: "Antiferromagnetic order induced by an applied magnetic field in a high-temperature superconductor"NATURE. 415. 299-302 (2002)
[Publications] Taniguchi K, Katsufuji T, Sakai F, Ueda H, Kitazawa K, Takagi H: "Charge dynazics and possibility of ferromagnetism in A_<1-x>La_xB_6 (A=Ca and Sr)"PHYSICAL REVIEW B. 66. 064407 (2002)
[Publications] Horii S, Takagi H, Ikuta H, Hussey NE, Hirabayashi I, Nizutani U: "Dinensionality of the Cu-O double-chain site of PrBa_2Cu_4O_8"PHYSICAL REVIEW B. 66:(5). 054530 (2002)
[Publications] Kobayashi K, Susaki T, Fujimori A, Tonogai T, Takagi H: "Disorder effects in the bipolaron system Ti_4O_7, studied by photoemission spectroscopy"EUROPHYSICS LETTERS. 59:(6). 868-874 (2002)
[Publications] Izawa K, Kamata K, Nakajima Y, Matsuda Y, Watanabe T, Nohara M, Takagi H, Thalmeier P, Maki K: "Gap function with point nodes in borocarbide superconductor YNi_2B_2C"PHYSICAL REVIEW LETTERS. 89:(13). 137006 (2000)
[Publications] Katsufuji T, Masaki M, Machida A, Moritono M, Kato K, Nishibori E, Takata H, Sakata M, Ohoyama K, Kitazawa K, Takagi H: "Crystal structure and magnetic properties of hexagonal RHnO_3 (R=Y, Lu, and Sc) and the effect of doping"PHYSICAL REVIEW B. 66:(13). 134434 (2002)
[Publications] Yuhki Kohsaka, Masaki Azuna, Ikuya Yamada, Takao Sasagawa, Tetsuo Hanaguri, Mikio Takano, Hidenori Takagi: "Growth of Na-Doped Ca_2CuO_2Cl_2 Single Crystals under High Pressures of Several GPa"J.Am.Chen.Soc. Vol.124,No.41. 12275-12278 (2002)
[Publications] Takaki K, Koizumi A, Hanaguri T, Nohara M, Takagi H, Kitazawa K, Kato Y, Tsuchiya Y, Kitano H, Maeda A: "Effects of superconducting gap anisotropy on the flux flow resistivity in Y(Ni_<1-x>Pt_x)(2)B_2C"Phys.Rev.B. 66:(18). 184511 (2002)
[Publications] Ueda H, Kitazawa K, Matsumoto T, Takagi H: "Charge transport near pressure-induced antiferromagnetic quantum critic al point in Magneli-phase vanadium oxides"Solid State Communications. 125:(2). 83-87 (2003)

2002 Fiscal Year Annual Research Report

新奇な量子流体の物質探索と相制御

Principal Investigator

高木 英典 東京大学, 大学院・新領域創成科学研究科, 教授 (40187935)

Research Products

[Publications] T.Nakajima, H.Kageyama, Y.Ueda: "Successive phase transitions in a metal-ordered manganite perovskite YBaMn_2O_4"J.Phys.Chem.Solids. 63. 913-916 (2002)

[Publications] Y.Ueda, M.Isobe, T.Yamauchi: "Superconductivity under high pressure in β(β')-vanadium bronzes"J.Phys.Chem.Solids. 63. 951-955 (2002)

[Publications] T.Yamauchi, Y.Ueda, N.Mori: "Pressure-Induced Superconductivity in β-Na_<0.33>V_2O_5 beyond Charge Ordering"Phys.Rev.Lett.. 89. 57002-1-57002-4 (2002)

[Publications] M.Isobe, Y.Ueda: "Observation of Phase Transition from Metal to Spin-Singlet Insulator in MgTi_2O_4 with S=1/2 Pyrochlore Lattice"J.Phys.Soc.Jpn.. 71. 1848-1851 (2002)

[Publications] T.Nakajima, Y.Ueda: "Structures and Electromagnetic Properties of New Metal-Ordered Manganite s : RBaMn_2O_6 (R=Y and Rare-Earth Elements)"J.Phys.Soc.Jpn.. 71. 2843-2846 (2002)

[Publications] Z.Hiroi, T.Yamauchi, T.Yamada, H.Hanawa, Y.Ohishi, O.Shinomura, H.Abliz, H.Hedo, Y.Uwatoko: "High-pressure study on the superconducting pyrochlore oxide Cd_2Re_2O_7"J.Phys.Chem.Solids. 71・6. 1553-1557 (2002)

[Publications] Z.Hiroi, J.Yamaura, Y.Muraoka, M.Hanawa: "Second phase transition in pyrochlore oxide Cd_2Re_2O_7"J.Phys.Soc.Jpn. 71・7. 1634-1636 (2002)

[Publications] Z.Hiroi, K.Matsuhira, S.Takagi, T.Tayaua, T.Sakakibara: "Specific heat of Kagome ice in the pyrochlore oxide Dy_2Ti_2O_7"J.Phys.Soc.Jpn. 72・2. 411-418 (2003)

[Publications] Ueda H, Nohara M, Kitazawa K, Takagi H, Fujinori A, Hizokawa T, Yagi T: "Copper pyrites CuS2 and CuSe2 as anion conductors"PHYSICAL REVIEW B. 65:(15). 115104 (2002)

[Publications] Hiroaki Ueda, Koichii Kitazawa, Hidenori Takagi, Takehiko Matsumoto: "Strong Carrier Concentration Dependence of Pressure Effect on Bipolaronic Transitions in Magneli Phase Ti_nO_<2n-1> (n=4,5,6)"J.Phys.Soc.Jpn. Vol.71,No.6. 1506-1510 (2002)

[Publications] C.Ulrich, S.Kondo, M.Reehuis, H.He, C.Bernhard, C.Niedermayer, F.Bouree, P.Bourges, M.Ohl, H.M.Ronnow, H.Takagi, B.Keimer: "Structural and magnetic instabilities of La_<2-x>Sr_xCaCu_2O_6"Phys.Rev.B. 65. 220507-1-220507-4 (2002)

[Publications] Lake B, Ronnow HM, Christensen NB, Aeppli G, Lefmann K, McMorrow DF, Vorderwisch P, Smeibidl P, Mangkorntong N, Sasagawa T, Nohara M, Takagi H, Mason TE: "Antiferromagnetic order induced by an applied magnetic field in a high-temperature superconductor"NATURE. 415. 299-302 (2002)

[Publications] Taniguchi K, Katsufuji T, Sakai F, Ueda H, Kitazawa K, Takagi H: "Charge dynazics and possibility of ferromagnetism in A_<1-x>La_xB_6 (A=Ca and Sr)"PHYSICAL REVIEW B. 66. 064407 (2002)

[Publications] Horii S, Takagi H, Ikuta H, Hussey NE, Hirabayashi I, Nizutani U: "Dinensionality of the Cu-O double-chain site of PrBa_2Cu_4O_8"PHYSICAL REVIEW B. 66:(5). 054530 (2002)

[Publications] Kobayashi K, Susaki T, Fujimori A, Tonogai T, Takagi H: "Disorder effects in the bipolaron system Ti_4O_7, studied by photoemission spectroscopy"EUROPHYSICS LETTERS. 59:(6). 868-874 (2002)

[Publications] Izawa K, Kamata K, Nakajima Y, Matsuda Y, Watanabe T, Nohara M, Takagi H, Thalmeier P, Maki K: "Gap function with point nodes in borocarbide superconductor YNi_2B_2C"PHYSICAL REVIEW LETTERS. 89:(13). 137006 (2000)

[Publications] Katsufuji T, Masaki M, Machida A, Moritono M, Kato K, Nishibori E, Takata H, Sakata M, Ohoyama K, Kitazawa K, Takagi H: "Crystal structure and magnetic properties of hexagonal RHnO_3 (R=Y, Lu, and Sc) and the effect of doping"PHYSICAL REVIEW B. 66:(13). 134434 (2002)

[Publications] Yuhki Kohsaka, Masaki Azuna, Ikuya Yamada, Takao Sasagawa, Tetsuo Hanaguri, Mikio Takano, Hidenori Takagi: "Growth of Na-Doped Ca_2CuO_2Cl_2 Single Crystals under High Pressures of Several GPa"J.Am.Chen.Soc. Vol.124,No.41. 12275-12278 (2002)

[Publications] Takaki K, Koizumi A, Hanaguri T, Nohara M, Takagi H, Kitazawa K, Kato Y, Tsuchiya Y, Kitano H, Maeda A: "Effects of superconducting gap anisotropy on the flux flow resistivity in Y(Ni_<1-x>Pt_x)(2)B_2C"Phys.Rev.B. 66:(18). 184511 (2002)

[Publications] Ueda H, Kitazawa K, Matsumoto T, Takagi H: "Charge transport near pressure-induced antiferromagnetic quantum critic al point in Magneli-phase vanadium oxides"Solid State Communications. 125:(2). 83-87 (2003)

高木英典東京大学, 大学院・新領域創成科学研究科, 教授 (40187935)