研究者詳細 - 野上　由夫

論文 - 野上　由夫

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Highly isotropic in-plane upper critical field in the anisotropic s-wave superconductor 2H-NbSe2 査読

S. Yasuzuka, S. Uji, S. Sugiura, T. Terashima, Y. Nogami, K. Ichimura, S. Tanda

J. Supercond. Nov. Magn. 33 ( 4 ) 953 - 958 2019年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

Resistivity measurements for a layered transition metal dichalcogenide 2H-NbSe2 were performed to investigate the in-plane anisotropy of the upper critical field (Hc2) for magnetic fields up to 14.5 T at temperatures down to 2.0 K. For fields rotated within the basal plane, the in-plane anisotropy of a characteristic field H∗ (defined as the field strength at which the resistivity reaches zero) showed twofold symmetry at low temperatures. On the basis of this result, the in-plane anisotropy of Hc2 and the superconducting gap structure in 2H-NbSe2 are discussed.

DOI： 10.1007/s10948-019-05333-z

Multiple charge density waves compete in ternary rare-earth nickel carbides, RNiC2 (R: Y, Dy, Ho, and Er) 査読

Maeda Hiroyuki, Kondo Ryusuke, Nogami Yoshio

PHYSICAL REVIEW B 100 ( 10 ) 2019年9月

2H-NbSe₂における上部臨界磁場の面内異方性

安塚周磨, 宇治進也, 杉浦栞理, 寺嶋太一, 野上由夫, 市村晃一, 丹田聡

日本物理学会講演概要集 73.2 1189 - 1189 2018年

A new strategy for inducing dipole moments in charge-transfer complexes: introduction of asymmetry into axially ligated iron phthalocyanines 査読

Masaki Matsuda, Sayaka Iwamura, Yumi Hamada, Hiroko Ohishi, Miki Nishi, Yoshio Nogami, Mitsuo Ikeda, Akinori Kanda, Yusuke Funasako, Tomoyuki Mochida, Akiko Nakao, Noriaki Hanasaki

DALTON TRANSACTIONS 46 ( 35 ) 11800 - 11805 2017年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

Introduction of asymmetry into charge-transfer complexes composed of axially ligated iron phthalocyanines was achieved. In the obtained crystals of TPP[Fe-III(Pc)(CN) Cl](2), TPP[FeIII(Pc)(CN) Br](2), and TPP [Fe-III(Pc) BrCl](2) (TPP = tetraphenylphosphonium and Pc = phthalocyanine), the axial positions of the iron atoms were occupied by 50/50 ratios of the ligands CN/Cl, CN/Br, and Br/Cl, respectively. The crystal structures of the obtained CT complexes were isostructural to those composed of the symmetric analogues of the type [Fe-III(Pc) L-2] (L = CN, Cl or Br); the [FeIII(Pc) LL'] units formed regular one-dimensional chains along the c-axis following the symmetry of the P4(2)/n space group. Despite forming similar regular chains to the symmetric systems, the electrical resistivities and activation energies were enhanced in the obtained CT complexes compared to those in symmetric systems, indicating that the charge-ordered states were stabilised by the introduction of asymmetry. More specifically, the dielectric relaxation behaviour of the inhomogeneous disordered TPP[FeIII(Pc)(CN) Cl](2) probably suggests that a dipole moment was induced in this material.

DOI： 10.1039/c7dt02605f

Interplay between charge density wave and antiferromagnetic order in GdNiC2 査読

N. Hanasaki, S. Shimomura, K. Mikami, Y. Nogami, H. Nakao, H. Onodera

PHYSICAL REVIEW B 95 ( 8 ) 2017年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

The correlation between the charge density wave (CDW) and f local moments is observed in GdNiC2 by means of x-ray diffraction in a magnetic field. Various kinds of electronic states exist in the magnetic field. The intensity of the CDW peak changes in the successive transitions and the commensurate-incommensurate transition of the CDW takes place as well. The successive transitions are explained in terms of a cooperative effect of the Peierls instability and the spin Friedel oscillation, in which the antiferromagnetic order of the f local moments is coupled to the spin density wave coexisting with the CDW of the conduction electron.

DOI： 10.1103/PhysRevB.95.085103

Possible charge order structure of stoichiometric YbFe2O4 査読

Kosuke Fujiwara, Tomoyuki Karasudani, Mamoru Fukunaga, Hiroyuki Kobayashi, Jun Kano, Pierre-Eymeric Janolin, Jean-Michel Kiat, Yoshio Nogami, Ryusuke Kondo, Naoshi Ikeda

FERROELECTRICS 512 ( 1 ) 85 - 91 2017年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：TAYLOR & FRANCIS LTD

We report a possible charge ordering model of triangular mixed valence material YbFe2O4. It was found that a crystal synthesized with high stoichiometry on iron vacancy shows new and simple extinction rule in the superlattice reflections. The Laue class of the diffraction signal is expressed as 2/m. With the consideration of the charge neutrality and the superlattice signal of (1/3 1/3 0), we derived 5 possible charge ordering models of this material.

DOI： 10.1080/00150193.2017.1349945

Observation of all-in type tetrahedral displacements in nonmagnetic pyrochlore niobates 査読

S. Torigoe, Y. Ishimoto, Y. Aoishi, H. Murakawa, D. Matsumura, K. Yoshii, Y. Yoneda, Y. Nishihata, K. Kodama, K. Tomiyasu, K. Ikeda, H. Nakao, Y. Nogami, N. Ikeda, T. Otomo, N. Hanasaki

PHYSICAL REVIEW B 93 ( 8 ) 2016年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We observed all-in type Nb tetrahedral displacement in nonmagnetic pyrochlore niobates A(2)Nb(2)O(7) (A = Nd0.5Ca0.5 and Y0.5Ca0.5) through the analysis of the neutron pair distribution function and the extended x-ray absorption function spectroscopy. The all-in type Nb tetrahedral displacement, which has the character of a charge singlet state, is driven by the formation of the bonding orbital. The diffuse scattering in the x-ray diffraction, which has the resonant component in the Nb L-3 edge, indicates that the all-in type Nb tetrahedral displacement has the periodicity with its short-range correlation.

DOI： 10.1103/PhysRevB.93.085109

低温強磁場X線カメラの開発と希土類化合物RNiC₂系への適用

近藤隆祐, 阿井幸男, 野上由夫

日本物理学会講演概要集 71 1806 - 1806 2016年

記述言語：日本語出版者・発行元：一般社団法人日本物理学会

<p>300Kから3Kまでの温度及び10Tまでの磁場下における構造変化を追跡するための高感度X線カメラの開発及び，当該装置を希土類化合物RNiC2系に適用した結果について報告する．RNiC2系は90K以上の高温においてCDW転移を起こすが，いくつかの物質で10-30K付近においてR原子上の局在スピンが磁気秩序すると，CDWの消失や振幅減少を起こすことが知られている.今回開発を報告する装置によって，磁場を用いてRNiC2結晶中のR原子上の局在スピンを制御した時のCDWの振る舞いを観測出来,この系の系統的な構造物性研究が可能になった．</p>

DOI： 10.11316/jpsgaiyo.71.2.0_1806

Photoinduced switching to metallic states in the two-dimensional organic Mott insulator dimethylphenazine-tetrafluorotetracyanoquinodimethane with anisotropic molecular stacks 査読

Matsuzaki Hiroyuki, Ohkura Masa-aki, Ishige Yu, Nogami Yoshio, Okamoto Hiroshi

PHYSICAL REVIEW B 91 ( 24 ) 2015年6月

Photoinduced switching to metallic states in the two-dimensional organic Mott insulator dimethylphenazine-tetrafluorotetracyanoquinodimethane with anisotropic molecular stacks 査読

Hiroyuki Matsuzaki, Masa-aki Ohkura, Yu Ishige, Yoshio Nogami, Hiroshi Okamoto

PHYSICAL REVIEW B 91 ( 24 ) 2015年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

A photoinduced phase transition was investigated in an organic charge-transfer (CT) complex M2P-TCNQF(4), [M2P: 5,10-dihydro-5,10-dimethylphenazine, donor (D) molecule; TCNQF(4): 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, acceptor (A) molecule] by means of femtosecond pump-probe reflection spectroscopy. This is an ionic compound and has a peculiar two-dimensional (2D) molecular arrangement; the same A (or D) molecules arrange along the [100] direction, and A and D molecules alternately arrange along the [111] direction. It results in a strongly anisotropic two-dimensional electronic structure. This compound shows a structural and magnetic phase transition at 122K below which the two neighboring molecules are dimerized along both the [100] and [111] directions. We demonstrate that two kinds of photoinduced phase transitions occur by irradiation of a femtosecond laser pulse; in the high-temperature lattice-uniform phase, a quasi-one-dimensional (1D) metallic state along the AA(DD) stack is generated, and in the low-temperature lattice-dimerized phase, a quasi-2D metallic state is initially produced and molecular dimerizations are subsequently released. Mixed-stack CT compounds consisting of DA stacks are generally insulators or semiconductors in the ground state. Here, such a dynamical metallization in the DA stack is demonstrated. The release of the dimerizations drives several kinds of coherent oscillations which play an important role in the stabilization of the lattice-dimerized phase. The mechanisms of those photoinduced phase transitions are discussed in terms of the magnitudes of the anisotropic bandwidths and molecular dimerizations along two different directions of the molecular stacks.

DOI： 10.1103/PhysRevB.91.245140

23pBE-12 パイロクロア型ニオブ酸化物におけるチャージシングレット状態の観測

鳥越秀平, 青石優平, 村川寛, 松村大樹, 吉井賢資, 米田安宏, 樹神克明, 池田一貴, 富安啓輔, 中尾裕則, 大友季哉, 野上由夫, 花咲徳亮

日本物理学会講演概要集 70 2325 - 2325 2015年

22pBA-17 希土類化合物RNiC_2(R=La, Ce)のホール効果2

野村勝史, 近藤隆祐, 野上由夫

日本物理学会講演概要集 70 2234 - 2234 2015年

Interplay of Charge-Density Wave and Magnetic Order in Ternary Rare-Earth Nickel Carbides, RNiC2 (R = Pr and Nd) 査読

Nobuki Yamamoto, Ryusuke Kondo, Hiroyuki Maeda, Yoshio Nogami

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 82 ( 12 ) 2013年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

The electrical and structural properties of NdNiC2 and PrNiC2 are examined in single-crystalline samples in order to investigate the interplay of charge-density wave (CDW) and magnetic order in ternary rare-earth nickel carbides, RNiC2, where R is a rare-earth element. PrNiC2 (no magnetic order down to 1.5 K) and NdNiC2 [antiferromagnetic (AF) transition at 17.2 K] show resistance anomalies at 89 and 121 K, respectively, which are revealed to be CDW transitions by observing X-ray satellite reflections. NdNiC2 also shows a gradual decrease in both resistivity and CDW amplitude below the Neel temperature. In the AF phase, the magnetoresistance sharply decreases where a ferromagnetic (FM) order occurs, which is realized above the spin-flop magnetic field. These results clearly suggest that the relationships between CDW and magnetic order in RNiC2 depend on whether the magnetic order is AF or FM.

DOI： 10.7566/JPSJ.82.123701

X-ray crystal structure analysis and Ru valence of Ba<inf>4</inf>Ru <inf>3</inf>O<inf>10</inf> single crystals 査読

Taichi Igarashi, Yoshio Nogami, Yannick Klein, Gwenaelle Rousse, Ryuji Okazaki, Hiroki Taniguchi, Yukio Yasui, Ichiro Terasaki

Journal of the Physical Society of Japan 82 ( 10 ) 2013年10月

掲載種別：研究論文（学術雑誌）

We present a single-crystalline x-ray diffraction study on Ba4Ru3O10 consisting of corner-shared Ru3O12 trimers. The crystal structure is redetermined from 78 to 300K across an antiferromagnetic transition at 105 K. The orthorhombic symmetry (Cmca, space group No. 64) is preserved at all temperatures measured. This structure presents exceptionally long Ru-O distances characterized by a significant distribution within the Ru 3O12 trimer. A bond valence sum calculation suggests that the charge disproportionation within the Ru3O12 trimer emerges even at room temperature, which we ascribe to molecular orbital formation in the Ru3O12 trimer, as supported by the results of recent theoretical calculations. On the basis of the analyzed crystal structure, the electronic states and the nature of the phase transition at 105K are discussed. © 2013 The Physical Society of Japan.

DOI： 10.7566/JPSJ.82.104603

Emergence of superconductivity at 45 K by lanthanum and phosphorus co-doping of CaFe2As2 査読

Kazutaka Kudo, Keita Iba, Masaya Takasuga, Yutaka Kitahama, Jun-ichi Matsumura, Masataka Danura, Yoshio Nogami, Minoru Nohara

SCIENTIFIC REPORTS 3 1478 2013年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

Co-doping of lanthanum and phosphorus in CaFe2As2 induces superconductivity at 45 K. This superconducting transition temperature is higher than the 38 K transition in Ba1-xKxFe2As2, which is the maximum found thus far among the 122 phases. Superconductivity with a substantial shielding volume fraction was observed at 0.12 <= x <= 0.18 and y = 0.06 in Ca1-xLaxFe2(As1-yPy)(2). The superconducting phase of the present system seems to be not adjacent to an antiferromagnetic phase.

DOI： 10.1038/srep01478

Thermoelectric Effect in Hexagonal Tungsten Oxides 査読

T. Okusako, T. Tokuyama, K. Mikami, Y. Nogami, N. Hanasaki

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 81 2012年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We synthesize hexagonal tungsten oxides CsxWO3 (x = 0.12 similar to 0.33) by the hydrothermal method and investigate their thermoelectric property. The title compounds show the metallic behavior. The Seebeck coefficient increases near the band edge in the small cesium ratio x. The maximal value of the power factor and the dimensionless figure of merit ZT are about 3 mu W/K(2)cm and 0.03, respectively.

DOI： 10.1143/JPSJS.81SB.SB028

Magnetic field switching of the charge-density-wave state in the lanthanide intermetallic SmNiC2 査読

N. Hanasaki, Y. Nogami, M. Kakinuma, S. Shimomura, M. Kosaka, H. Onodera

PHYSICAL REVIEW B 85 ( 9 ) 2012年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

In the intermetallic SmNiC2, the ferromagnetic metallic state competes with the charge-density-wave state. We can switch the charge-density-wave state by applying a magnetic field that is conjugated to the magnetization of the order parameter in the ferromagnetic state, and show the giant negative magnetoresistance. Under the applied magnetic field, the resistivity becomes one order of magnitude smaller than the zero-field resistivity.

DOI： 10.1103/PhysRevB.85.092402

Optical and structural studies of a two-dimensional organic Mott insulator dimethylphenazine-tetrafluorotetracyanoquinodimethane

M. Ohkura, Y. Ishige, R. Sawada, H. Matsuzaki, H. Matsuzaki, Y. Nogami, H. Nishikawa, M. Yamashita, S. Horiuchi, S. Horiuchi, H. Okamoto, H. Okamoto, H. Okamoto

Physical Review B - Condensed Matter and Materials Physics 84 2011年8月

Electronic structure of an organic charge-transfer complex, M 2P-TCNQF4 (M2P: 5,10-dihydro-5,10- dimethylphenazine; TCNQF4: 2,3,5,6-tetrafluoro-7,7,8,8- tetracyanoquinodimethane), was investigated by means of optical reflection spectroscopy and x-ray structural analyses. This is an ionic compound and has a unique quasi-two-dimensional (2D) crystal structure in which donor (D) molecules of M2P and acceptor (A) molecules of TCNQF4 stack respectively along the [100] direction, and D and A molecules also stack alternately along the [111] direction. We evaluated the transfer energy t(AA) between the neighboring A molecules, t(DD) between the neighboring D molecules along the [100] direction, and t(DA) between the neighboring D and A molecules along the [111] direction to be 43 meV, 29 meV, and 67 meV at room temperature, respectively. This demonstrates that an anisotropic 2D electronic structure is formed. By comparing the spectra of the imaginary part of the dielectric constant ε2 obtained from the polarized reflectivity spectra with the absorption spectrum of K-TCNQF4 and the ε2 spectra of M2P-PF6, which are composed of 1D A stacks and D stacks, respectively, it was revealed that in M2P-TCNQF4 the optical gap corresponds to the Mott gap transition from A- to A-, and the D+ to D+ transition and the A - to D+ transition or equivalently the charge-transfer (CT) transition located at the higher energies. Below the structural and magnetic phase transition temperature Tc ∼ 122 K, spin-singlet states are formed via displacements of both D and A molecules. The pattern of molecular displacements was found to be very unique, indicating that the phase transition cannot be attributed to a spin-Peierls-like mechanism. The nature of the phase transition is discussed from the temperature dependences of molecular displacements as well as of the Mott-gap transition and the CT transition. © 2011 American Physical Society.

DOI： 10.1103/PhysRevB.84.085136

Optical and structural studies of a two-dimensional organic Mott insulator dimethylphenazine-tetrafluorotetracyanoquinodimethane 査読

M. Ohkura, Y. Ishige, R. Sawada, H. Matsuzaki, Y. Nogami, H. Nishikawa, M. Yamashita, S. Horiuchi, H. Okamoto

PHYSICAL REVIEW B 84 ( 8 ) 2011年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Electronic structure of an organic charge-transfer complex, M2P-TCNQF(4) (M2P: 5,10-dihydro-5,10-dimethylphenazine; TCNQF(4): 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane), was investigated by means of optical reflection spectroscopy and x-ray structural analyses. This is an ionic compound and has a unique quasi-two-dimensional (2D) crystal structure in which donor (D) molecules of M2P and acceptor (A) molecules of TCNQF(4) stack respectively along the [100] direction, and D and A molecules also stack alternately along the [111] direction. We evaluated the transfer energy t(AA) between the neighboring A molecules, t(DD) between the neighboring D molecules along the [100] direction, and t(DA) between the neighboring D and A molecules along the [111] direction to be 43 meV, 29 meV, and 67 meV at room temperature, respectively. This demonstrates that an anisotropic 2D electronic structure is formed. By comparing the spectra of the imaginary part of the dielectric constant epsilon 2 obtained from the polarized reflectivity spectra with the absorption spectrum of K-TCNQF(4) and the epsilon(2) spectra of M2P-PF6, which are composed of 1D A stacks and D stacks, respectively, it was revealed that in M2P-TCNQF(4) the optical gap corresponds to the Mott gap transition from A(-) to A(-), and the D+ to D+ transition and the A(-) to D+ transition or equivalently the charge-transfer (CT) transition located at the higher energies. Below the structural and magnetic phase transition temperature T-c similar to 122 K, spin-singlet states are formed via displacements of both D and A molecules. The pattern of molecular displacements was found to be very unique, indicating that the phase transition cannot be attributed to a spin-Peierls-like mechanism. The nature of the phase transition is discussed from the temperature dependences of molecular displacements as well as of the Mott-gap transition and the CT transition.

DOI： 10.1103/PhysRevB.84.085136

Successive Transition in Rare-earth Intermetallic Compound GdNiC(2) 査読

N. Hanasaki, K. Mikami, S. Torigoe, Y. Nogami, S. Shimomura, M. Kosaka, H. Onodera

INTERNATIONAL CONFERENCE ON FRUSTRATION IN CONDENSED MATTER (ICFCM) 320 2011年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

In GdNiC(2), the magnetic state is investigated under the high magnetic fields and the low temperatures. We find the intermediate phases, in which the magnetization value is close to a half of the full moment, and the successive transition in the phase boundary between the antiferromagnetic, the metamagenetic, and the paramagnetic phases. The mechanism of the intermediate phase is discussed.

DOI： 10.1088/1742-6596/320/1/012072

X-ray Absorption Spectra in Pyrochlore Niobates 査読

S. Torigoe, Y. Ishimoto, N. Hanasaki, Y. Nogami, D. Matsumura, K. Yoshii, Y. Yoneda, Y. Nishihata

INTERNATIONAL CONFERENCE ON FRUSTRATION IN CONDENSED MATTER (ICFCM) 320 2011年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

The X-ray absorption spectra reveal that the valence of the Nb ion, and the displacement of the Nb ions from the center of the oxygen octahedra in the pyrochlore niobates YCaNb(2)O(7) and NdCaNb(2)O(7), which is consistent with the previous report of the neutron diffraction.

DOI： 10.1088/1742-6596/320/1/012078

Hydrothermal Synthesis of Hexagonal Vanadium Oxide 査読

T. Tokuyama, T. Okusako, K. Mikami, N. Hanasaki, Y. Nogami

INTERNATIONAL CONFERENCE ON FRUSTRATION IN CONDENSED MATTER (ICFCM) 320 2011年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

We synthesize the hexagonal vanadium oxide containing the alkaline-metal ion (Li, Na, and K). The crystal belongs to the magnetoplumbite-type structure. The title compound, in which the vanadium valance is not an integer, shows the metallic and the paramagnetic behavior. The electronic specific heat coefficient gamma is 34.7 mJ/K(2)mol, which is perhaps due to the spin fluctuation.

DOI： 10.1088/1742-6596/320/1/012073

Field-Induced Successive Phase Transitions in the Charge Density Wave Organic Conductor HMTSF-TCNQ 査読

Keizo Murata, Keiichi Yokogawa, Kensuke Kobayashi, Kosuke Masuda, Takahiko Sasaki, Yuki Seno, Natarajan Rani Tamilselvan, Harukazu Yoshino, James S. Brooks, Denis Jerome, Klaus Bechgaard, Mikio Uruichi, Kyuya Yakushi, Yoshio Nogami, Reizo Kato

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 79 ( 10 ) 2010年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

The magnetoresistance of quasi-1D two-chain organic conductor HMTSF-TCNQ (hexamethylenetetraselenafulvalene-tetracyanoquinodimethane), which shows charge density wave transition at ambient pressure, was studied under pressure up to 27 T and 31 T, in two high field facilities. We found a kink structure in the magnetoresistance reminiscent of field-induced spin density wave at an intermediate pressure of 1.5 GPa between 0 and 2 GPa. We speculate that these are successive quantum phases induced by magnetic field.

DOI： 10.1143/JPSJ.79.103702

Relaxation of geometrical frustration in NbSe3 topological crystals 査読

T. Tsuneta, K. Yamamoto, N. Ikeda, Y. Nogami, T. Matsuura, S. Tanda

PHYSICAL REVIEW B 82 ( 1 ) 2010年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Here we report the structural study of NbSe3 topological crystals via synchrotron x-ray measurements on individual microcrystals. Topological crystals are characterized by the shape of a ring or a twisted loop, thereby representing a translational and orientational order confined in topologically nontrivial, curved geometries. The crystal lattice of topological crystals is under considerable amount of strain. The volume-averaged strain asymptotically increases with thickness and curvature of a crystal. We present a structural model in which a ring crystal is composed of well-ordered domains in the shape of concentric cylinders. The internal structure reflects periodic accumulation and release of strain during the growth.

DOI： 10.1103/PhysRevB.82.014105

Pressure effect on the competing charge ordered states in theta-(BEDT-TTF)(2)CsZn(SCN)(4) 査読

M. Watanabe, M. Osanai, Y. Dohi, Y. Ishikawa, Y. Noda, Y. Nogami, I. Terasaki, H. Mori, T. Mori

PHYSICA B-CONDENSED MATTER 405 ( 11 ) S229 - S231 2010年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The pressure effect on the competing charge ordered states in theta-(BEDT-TTF)(2)CsZn(SCN)(4) was investigated by X-ray diffraction method Under 1 1 GPa the threefold long range ordered superstructure with the wave vector q(1) = (-2/3 0 1/3) was detected below 240 K and the twofold charge ordering with the wave vector q(2) = (0 0 1/2) was suppressed from 3 to 300 K by the pressure (C) 2010 Elsevier B V All rights reserved

DOI： 10.1016/j.physb.2010.03.018

Nonequilibrium charge ordering in theta-(BEDT-TTF)(2)MM '(SCN)(4) (M=Rb, Cs; M '=Co, Zn) 査読

Ichiro Terasaki, Shuichi Tasaki, Shigeru Ajisaka, Yoshio Nogami, Noriaki Hanasaki, Masashi Watanabe, Hatsumi Mori, Takehiko Mori

PHYSICA B-CONDENSED MATTER 405 ( 11 ) S217 - S220 2010年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Giant nonlinear conduction in the charge ordered organic conductor theta-(BEDT-TTF)(2)MM'(SCN)(4) (M = Cs Rb M' = Co Zn) is analyzed in relation to the current-induced suppression of the charge ordered state characterized by a wave vector of q(2) = (0k 1/2) On the basis of a theory of the nonequilibrium Peierls transition the energy gap is calculated as a function of current density J(ext) which is found to depend weakly on temperature in an intermediate temperature range This justifies the evaluation of the found to be consistent with the calculation We compare the present results with nonequilibrium and Ail i IS charge-order energy gap Delta from the nonlinear resistivity rho assuming rho proportional to exp[Delta(J(ext))/k(B)T] and Delta(J(ext)) superconducting states induced by excess quasiparticles and discuss a mechanism of current-Induced suppression of the charge ordering in the title compound (C) 2009 Elsevier B V All rights reserved

DOI： 10.1016/j.physb.2009.11.073

Charge Order Competition Leading to Nonlinearity in Organic Thyristor Family 査読

Yoshio Nogami, Noriaki Hanasaki, Masashi Watanabe, Kenichiro Yamamoto, Takayoshi Ito, Naoshi Ikeda, Hiroyuki Ohsumi, Hidenori Toyokawa, Yukio Noda, Ichiro Terasaki, Hatsumi Mori, Takehiko Mori

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 79 ( 4 ) 2010年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

Simultaneous synchrotron radiation and transport measurements for the organic thyristor family compound theta-(BEDT-TTF)(2)RbZn(SCN)(4) have revealed the presence of microscopic competing domains between the twofold and 3 x 4 charge orderings in a triangular lattice. In contrast to conventional correlated electron systems, charge ordering is a unique critical parameter of phase competition. With external current, only the twofold ordering melts, which is responsible for the emergence of a nonlinear response.

DOI： 10.1143/JPSJ.79.044606

Interplay of charge-density waves and superconductivity in the organic conductor beta ''-(BEDT-TTF)(2)AuBr2 査読

Ryusuke Kondo, Momoka Higa, Seiichi Kagoshima, Noriaki Hanasaki, Yoshio Nogami, Hiroyuki Nishikawa

PHYSICAL REVIEW B 81 ( 2 ) 2010年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We studied the low-temperature electrical properties of the two-dimensional organic conductor beta ''-(BEDT-TTF)(2)AuBr2, whose electronic structure is similar to that of the pressure-induced superconductor beta ''-(DODHT)(2)PF6 having a charge-ordered transition at 255 K at ambient pressure. We found that the ground state of beta ''-(BEDT-TTF)(2)AuBr2 at ambient pressure has a charge-density-wave phase below 6.5 K accompanied by x-ray superlattice spots. We also discovered superconductivity in the vicinity of the charge-density-wave phase by applying uniaxial strain. Based on the obtained results, we propose a unified electronic phase diagram that suggests the relationships among the charge-ordered insulating state, the superconducting phase, and the charge-density-wave phase in beta ''-type organic conductors. The phase diagram shows that the superconducting phase is located near the charge-density-wave phase, which suggests that spin fluctuations play a minor role in the mechanism of the superconductivity and sheds light on the possibility of charge-fluctuation-mediated superconductivity in this type of organic conductor.

DOI： 10.1103/PhysRevB.81.024519

Commensurate-incommensurate urate transition of charge density waves in o-TaS3 査読

K. Inagaki, M. Tsubota, K. Ichimura, S. Tanda, K. Yamamoto, N. Hanasaki, Y. Nogami, N. Ikeda, T. Ito, H. Toyokawa

PHYSICA B-CONDENSED MATTER 404 ( 3-4 ) 396 - 398 2009年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

We report a synchrotron X-ray study of charge density waves (CDWs) in an o-TaS3 crystal. CDW of o-TaS3 has been known to undergo a commensurate-incommensurate transition at 100 K, below which the wavevector locks in with the pristine lattice. However, the details of the commensurate-incommensurate transition remain open problems, the example being whether the discommensuration exists or not in the neighborhood of the transition. We exploited the beamline BL02B1 of SPring-8. A two-dimensional detector was placed at a distance of 1300mm from the sample, providing an angle resolution of 0.0076 degrees. Temperature dependence of the Bragg peak (0 0 2) and satellite peak (1 - 12) + q was measured from 7 to 180 K. We found that a new phase in the temperature range of 130-50 K, where two independent CDWs coexist. These waves are incommensurate and commensurate CDWs with longitudinal wave vectors q(c) = 0.252c* and 0.250c*, respectively. By lowering the temperature, intensity of the incommensurate CDW was decreased, while that of the commensurate CDW was increased. Below 50K, the incommensurate CDW was completely diminished. Based on the concept of discommensuration, we suggested the dislocation configuration from the intensity of the two CDWs. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2008.11.017

Current-Density Dependence of the Charge-Ordering Gap in the Organic Salt theta-(BEDT-TTF)(2)CsM(SCN)(4) (M = Zn, Co, and Co0.7Zn0.3) 査読

Fumiaki Sawano, Tomohiro Suko, Taichi S. Inada, Shuichi Tasaki, Ichiro Terasaki, Hatsumi Mori, Takehiko Mori, Yoshio Nogami, Naoshi Ikeda, Masashi Watanabe, Yukio Noda

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 ( 2 ) 2009年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We have measured and analyzed the resistivity and voltage-current characteristics of the charge-ordered organic salt theta-(BEDT-TTF)(2)CsM(SCN)(4) (M = Zn, Co, and Co(0.7)Z(0.3)). At 4.3 K, all the samples show giant nonlinear conduction, in which the c-axis resistivity markedly decreases with external current by a factor of 10 against a small electric field of 1 V/cm. The temperature dependence of the resistivity is well described by an activation law, the activation energy of which is evaluated to be 2 meV in the low-current limit, and linearly decreases with external current. The activation energy and x-ray intensity near q(2) = (0, k, 1/2) are found to show the same dependence on current density. This coincidence strongly suggests that the energy gap of the charge order indexed by q(2) is an order parameter of this phenomenon.

DOI： 10.1143/JPSJ.78.024714

Synchrotron X-ray study of charge density waves in o-TaS3 査読

K. Inagaki, M. Tsubota, K. Ichimura, S. Tanda, K. Yamamoto, N. Hanasaki, Y. Nogami, N. Ikeda, T. Ito, H. Toyokawa

25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 4 150 2009年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

We report a synchrotron X-ray study of charge density waves (CDW) in an o-TaS3 crystal. CDW of o-TaS3 has been known to undergo a commensurate-incommensurate transition at 100 K, below which the wavevector locks in with the pristine lattice. We exploited the beamline BL02B1 of SPring-8. Temperature dependence of the Bragg peak (002) and satellite peak (1 -1 2)+(q) over right arrow was measured from 7 K to 180 K. We found that a new phase in a temperature range of 130-50 K, where two independent CDWs coexist. These waves are incommensurate and commensurate CDWs with longitudinal wave vectors q(c)=0.252c* and 0.250c*, respectively. By lowering the temperature, intensity of the incommensurate CDW was decreased, while that of the commensurate CDW was increased. At 50 K, the incommensurate CDW was completely diminished. Based on the concept of discommensuration, we determined the dislocation configuration from the intensity of the two CDWs.

DOI： 10.1088/1742-6596/150/4/042068

Temperature and electric-current dependence of charge-ordered domains in theta-(BEDT-TTF)(2)CsZn(SCN)(4) 査読

T. Ito, M. Watanabe, K. -I. Yamamoto, N. Ikeda, Y. Nogami, Y. Noda, H. Mori, T. Mori, I. Terasaki

EPL 84 ( 2 ) 2008年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY

We report X-ray diffraction measurements of the charge-ordered organic conductor theta-(BEDT-TTF)(2)CsZn(SCN)(4) at various temperatures with external currents. The two kinds of diffuse scattering observed at q(1) = (2/3 k 1/3) and q(2) = (0 k 1/2) exhibit remarkable difference in the interplane correlation along the b-axis, the temperature dependence, and the electric-current dependence. These observations suggest that the two diffuse scatterings come from spatially different charge-ordered domains. The external current melts the q(2)-type domains, which can control the competition of the two orders. Copyright (C) EPLA, 2008

DOI： 10.1209/0295-5075/84/26002

Field-induced discommensuration in charge density waves in o-TaS3 査読

Katsuhiko Inagaki, Masakatsu Tsubota, Kazuki Higashiyama, Koichi Ichimura, Satoshi Tanda, Kenichiro Yamamoto, Noriaki Hanasaki, Naoshi Ikeda, Yoshio Nogami, Takayoshi Ito, Hidenori Toyokawa

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 9 ) 2008年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We report a synchrotron X-ray Study of charge density waves (CDWs) in an o-TaS3 crystal. We found that two independent CDWs coexist ill the temperature range of 130-50K. These waves are incommensurate and commensurate CDWs with longitudinal wave vectors q(c) = 0.252c* and 0.250c*, respectively. The temperature and electric current dependences of the intensity of the two CDW satellites were measured. We found that the commensurate CDW was converted to the incommensurate CDW at 80 K by inducing current flow. Our observation was interpreted in terms of the dynamics of topological defects. We determined the edge dislocation configuration from the electric Current dependence of the intensity of the two CDWs. The result implies Cor the first time that discommensurations are induced ill the commensurate CDW by applying an electric field.

DOI： 10.1143/JPSJ.77.093708

Hump Like Resistance Anomaly in Organic Conductor β"-(BEDT-TTF)_2CsCd(SCN)_4

Kondo Ryusuke, Otsuji Jun, Kagoshima Seiichi, NOGAMI Yoshio

Journal of the Physical Society of Japan 77 ( 6 ) "63702 - 1"-"63702-4" 2008年6月

記述言語：英語出版者・発行元：一般社団法人日本物理学会

We investigate the low-temperature electronic phase of a two-dimensional organic conductor, β"-(BEDT-TTF)_2CsCd(SCN)_4 [where BEDT-TTF denotes bis(ethylenedithio)tetrathiafulvalene], which has a large hump between 32 and around 5K in the temperature dependence of the interlayer resistance. We present experimental results for the temperature dependence of the resistance under magnetic fields and its Kohler plots, and an x-ray diffraction study. We find that I) Kohler's rule is strongly violated below 32K, although the rule is valid above 32K, and II) weak superlattice spots appear at 15.6K in the x-ray study. On the basis of the experimental results, we suggest that the origin of the resistance hump is the formation of a possible charge density wave transition at about 32K by the nesting of a pair of large one-dimensional Fermi surfaces obtained in the electronic structure calculation based on the crystal structure at room temperature.

Non-thermal evidence for current-induced melting of charge order in theta-(BEDT-TTF)(2)CsZn(SCN)(4) 査読

Masashi Watanabe, Kenichiro Yamamoto, Takayoshi Ito, Yusaku Nakashima, Makoto Tanabe, Noriaki Hanasaki, Naoshi Ikeda, Yoshio Nogami, Hiroyuki Ohsumi, Hidenori Toyokawa, Yukio Noda, Ichiro Terasaki, Fumiaki Sawano, Tomohiro Suko, Hatsumi Mori, Takehiko Mori

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 6 ) 2008年6月

Hump like resistance anomaly in organic conductor beta ''-(BEDT-TTF)(2)CsCd(SCN)(4) 査読

Ryusuke Kondo, Jun Otsuji, Seiichi Kagoshima, Yoshio Nogami

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 6 ) 2008年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We investigate the low-temperature electronic phase of a two-dimensional organic conductor, (BEDT-TTF)(2)CsCd(SCN)(4) [where BEDT-TTF denotes bis(ethylenedithio)tetrathiafulvalene], which has a large hump between 32 and around 5 K in the temperature dependence of the interlayer resistance. We present experimental results for the temperature dependence of the resistance under magnetic fields and its Kohler plots, and an x-ray diffraction study. We find that I) Kohler's rule is strongly violated below 32 K, although the rule is valid above 32 K, and II) weak superlattice spots appear at 15.6 K in the x-ray study. On the basis of the experimental results, we suggest that the origin of the resistance hump is the formation of a possible charge density wave transition at about 32 K by the nesting of a pair of large one-dimensional Fermi surfaces obtained in the electronic structure calculation based on the crystal structure at room temperature.

DOI： 10.1143/JPSJ.77.063702

Relaxation of geometrical frustration in NbSe3 topological crystals 査読

Tsuneta Taku, Nogami Yoshio, Yamamoto Kenichirou, Ikeda Naoshi, Tanda Satoshi

ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES 64 C509 - C509 2008年

Spin-Peierls transition in the charge-ordered organic conductor theta-BEDT-TTF2RbZn(SCN)(4) 査読

Masashi Watanabe, Yukio Noda, Yoshio Nogami, Hatsumi Mori

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 ( 12 ) 2007年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

X-ray investigation of theta-BEDT-TTF2RbZn(SCN)4 was carried out around the temperature of the phase transition to the nonmagnetic state. theta-BEDT-TTF2RbZn(SCN)4 exhibits a metal-insulator transition accompanied by a charge ordering at T-CO = 200 K. In the one-dimensional spin chain formed by this charge ordering, BEDT-TTF donor molecules are aligned uniformly along the a-axis obeying the 2(1) screw symmetry of the space group P2(1)2(1)2(1) below Tco. At the ground state, the system becomes nonmagnetic. The transition temperature T-c to the nonmagnetic phase seems to scatter around 20 K and may depend on the sample. We found that the extinction rule of [h00: It = 2n] no longer applied below approximately 20 K. This indicated a symmetry breaking of the 2(1) screw symmetry along the a-axis in the nonmagnetic state. The observed peak intensities violating the extinction rule were about 10(-4) of other general Bragg reflection. peak intensities. This structural change should be interpreted as a spin-Peierls transition in the charge-ordered system. In addition, a corresponding anomaly was observed in the lattice parameter a.

DOI： 10.1143/JPSJ.76.124602

Charge ordering in organic conductors 査読

Toshihiro Takahashi, Yoshio Nogami, Kyuya Yakushi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 75 ( 5 ) 2006年5月

記述言語：英語出版者・発行元：PHYSICAL SOC JAPAN

Present status of experiments on charge ordering (CO) phenomena observed in organic molecular conductors is reviewed. Experimental techniques to detect and analyze the CO, i.e., NMR, X-ray and Infrared/Raman spectroscopy, are described and the experimental results in typical materials exhibiting CO are summarized. (DI-DCNQI)(2)Ag, (TMTTF)(2)X, alpha-(BEDT-TTF)(2)I-3, theta-(BEDT-TTF)(2)RbZn(SCN)(4) and related materials are discussed. Charge disproportionation without long-range order observed in numbers of materials are also included.

DOI： 10.1143/JPSJ.75.051008

Is the two dimensional organic Conductor, iota-(EDO-S,S-DMEDT-TTF)(2)(AuCl2)(1+y) clean or dirty? 査読

T. Nakanishi, S. Yasuzuka, M. Teramura, L. Li, T. Fujimoto, T. Sasaki, T. Konoike, T. Terashima, S. Uji, Y. Nogami, G. C. Anyfantis, G. C. Papavassiliou, Keizo Murata

JOURNAL OF LOW TEMPERATURE PHYSICS 142 ( 3-4 ) 247 - 252 2006年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER/PLENUM PUBLISHERS

The transport properties of organic tau-type conductors seem to be very clean as well as very dirty depending on what we observe. To clarify this problem, we studied temperature and magnetic field dependence of resistivity, rho(T, B), in tau-(EDO-S,S-DMEDT-TTF)(2)(AuCl2)(1+y). The properties that favor "probably dirty" are: i) stepwise rho(a)(T) increase below 20 K, which is suppressed by magnetic field, and ii) contrasted difference in rho(T) as well as magnetization M(T) between field cooled (FC) and zero field cooled (ZFC). On the other hand, Shubnikov de Haas oscillations with very low Dingle temperature (T-D = 1.5 K) are typical of clean system. Based on these observations, we conclude this system changes from "dirty" to "clean" system by increase of magnetic field.

DOI： 10.1007/s10909-006-9195-7

X-ray and neutron transparent pulse magnets 査読

E. Ohmichi, N. Ikeda, Y. Nogami, T. Osada

YAMADA CONFERENCE LX ON RESEARCH IN HIGH MAGNETIC FIELDS 51 498 - + 2006年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

A new type of pulse magnet, x-ray and neutron transparent pulse magnet, is suggested for use in high-field diffraction experiments. The magnet is made of aluminum-based material, so we expect that the scattered beam penetrates the magnet body and hence the total number of reflection points available substantially increases. This feature possibly allows full determination of the lattice and magnetic structure in strong magnetic fields. To realize this idea, we constructed a prototype transparent magnet consisting of aluminum wire and duralumin reinforcement. With a portable capacitor bank, the maximum field of 25 T was successfully generated in a 1.6 mm bore, even though the aluminum wire is less strong and less conducting than copper wire. Since the total energy is small (E-bank similar to 100 J), high repetition rate, which is necessary for sufficient signal-to-noise ratio, is realized. Technical details, coil performance, and future prospects will be described.

DOI： 10.1088/174-6596/51/1/113

クリスタリット

坂田修身, 乾雅祝, 大高理, 木原國昭, 大嶋建一, 石沢伸夫, 八島正知, 川路均, 道上勇一, 野上由夫, 福永俊晴

日本結晶学会誌 48 ( 1 ) 92 - 96 2006年

X-ray structural study of charge and anion orderings of TMTTF salts 査読

Y Nogami, T Ito, K Yamamoto, N Irie, S Horita, T Kambe, N Nagao, K Oshima, N Ikeda, T Nakamura

JOURNAL DE PHYSIQUE IV 131 39 - 42 2005年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：EDP SCIENCES S A

High resolution X-ray structure analyses and electronic structure calculation revealed the condition for the charge ordering(CO) observed in the (TMTTF)(2)X (Fabre) salts. The phase diagram of the electronic states including 2k(F) and 4k(F) CO has been proposed associated with magnitudes Of Molecular dimerization and tetramerization.

DOI： 10.1051/jp4:2005131008

Evidence of band-filling control of tau-type organic conductors by thermal treatment 査読

H Yoshino, T Nakanishi, L Li, K Murata, D Graf, ES Choi, JS Brooks, Y Nogami, GC Papavassiliou

SYNTHETIC METALS 153 ( 1-3 ) 453 - 456 2005年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

The two dimensional (2D) organic conductor tau-(EDO-S,S-DMEDT-TTF)(2)(AuBr2)(1+y), (y <= 0.875) is known to exhibit sample dependence of the electric resistivity. The present authors assumed that the possible difference in y is responsible for the sample dependence and the amount of y can be effectively controlled for each crystal by thermal treatment. If it is the case,the band filling of the present compound can be also controlled. To observe the change in the band filling directly, the magnetoresistance was measured up to 45 T at 0.5 K for the magnetic field perpendicular to the conducting ab plane of the samples from one single crystal, one of which had been heated up to 400 K. Both the samples showed the two series of Shubnikov-de Haas oscillations of the magnetoresistance as reported previously. We, however, found the remarkable difference in the frequency of the slower oscillations between the virgin and heated samples. The X-ray study revealed that the thermal treatment does not affect the crystal structure related to the 2D band structure. Thus the frequency change by the thermal treatment is caused by the change in the band filling and it is tuned by heating the crystal.

DOI： 10.1016/j.synthmet.2005.07.329

An organic thyristor 査読

F Sawano, Terasaki, I, H Mori, T Mori, M Watanabe, N Ikeda, Y Nogami, Y Noda

NATURE 437 ( 7058 ) 522 - 524 2005年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

Thyristors are a class of nonlinear electronic device that exhibit bistable resistance - that is, they can be switched between two different conductance states(1). Thyristors are widely used as inverters ( direct to alternating current converters) and for the smooth control of power in a variety of applications such as motors and refrigerators. Materials and structures that exhibit nonlinear resistance of this sort are not only useful for practical applications: they also provide systems for exploring fundamental aspects of solid- state and statistical physics. Here we report the discovery of a giant nonlinear resistance effect in the conducting organic salt(2) theta- ( BEDT- TTF) 2CsCo( SCN)(4), the voltage- current characteristics of which are essentially the same as those of a conventional thyristor. This intrinsic organic thyristor works as an inverter, generating an alternating current when a static direct- current voltage is applied. Whereas conventional thyristors consist of a series of diodes ( their nonlinearity comes from interface effects at the p- n junctions), the present salt exhibits giant nonlinear resistance as a bulk phenomenon. We attribute the origin of this effect to the current-induced melting of insulating charge- order domains, an intrinsically non- equilibrium phenomenon in the sense that ordered domains are melted by a steady flow.

DOI： 10.1038/nature04087

Determination of Band-filling Change in the Two-dimensional Organic Conductor, τ-(EDO-S, S-DMEDT-TTF)_2(AuBr_2)_<1+y>, (y≦0.875) by the Quantum Oscillation of Magnetoresistance

Yoshino Harukazu, Murata Keizo, Nakanishi Tsutomu, LI Lin, CHOI Eun Sang, GRAF David, BROOKS James S, NOGAMI Yoshio, PAPAVASSILIOU George C

Journal of the Physical Society of Japan 74 ( 1 ) 417 - 424 2005年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本物理学会

The effect of thermal treatment on the transport properties is studied for a two-dimensional organic conductor τ-(EDO-S, S-DMEDT-TTF)_2(AuBr_2)_<1+y>, (y&le;0.875). The temperature dependence of the electric resistivity below room temperature was found to be changed from metallic down to low temperature to semiconducting by heating up to 420K. One of the two frequencies of Shubnikovde Haas oscillations are found to be different between the non-heated and heated parts from a single crystal, while no evidence of structural change in X-ray photograph was observed. The present result clearly shows that nominal valence or band filling can be controlled by simple thermal treatment for the quasi-two-dimensional organic metal. The mechanism of the change in the band filling is discussed in terms of anion decomposition.

DOI： 10.1143/JPSJ.74.417

Determination of band-filling change in the two-dimensional organic conductor, tau-(EDO-S,S-DMEDT-TTF)(2)(AuBr2)(1+y), (y <= 0.875) by the quantum oscillation of magnetoresistance 査読

H Yoshino, K Murata, T Nakanishi, L Li, ES Choi, D Graf, JS Brooks, Y Nogami, GC Papavassiliou

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 74 ( 1 ) 417 - 424 2005年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

The effect of thermal treatment on the transport properties is studied for a two-dimensional organic conductor tau-(EDO-S,S-DMEDT-TTF)(2)(AuBr2)(1+y), (y less than or equal to 0.875). The temperature dependence of the electric resistivity below room temperature was found to be changed from metallic down to low temperature to semiconducting by heating up to 420K. One of the two frequencies of Shubnikovde Haas oscillations are found to be different between the non-heated and heated parts from a single crystal, while no evidence of structural change in X-ray photograph was observed. The present result clearly shows that nominal valence or band filling can be controlled by simple thermal treatment for the quasi-two-dimensional organic metal. The mechanism of the change in the band filling is discussed in terms of anion decomposition.

DOI： 10.1143/JPSJ.74.417

Structural phase transition in two-dimensional kagome antiferromagnet m-N-methylpyridinium alpha-nitronyl nitroxide center dot BF4 center dot 1/3(Acetone) 査読

T Kambe, Y Nogami, K Oshima, W Fujita, K Awaga

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 4 ) 796 - 799 2004年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We found for the first time a structural phase transition in two-dimensional kagome antiferromagnet m-N-methylpyridinium alpha-nitronyl nitroxide (m-MPYNN)(.)BF(4)(.)1/3 (acetone). As, below T-s = 128.7 K, the intense satellite reflections are clearly observed at the modulation wave vector of q(s) = (1/3, 1/3, 0), the unit cell of the low-temperature phase is enlarged to root3a x root3a x c. In the low-temperature phase, the space group is determined to be P31c. The orientation of acetone molecules orders below T-s, leading to the lack of the three-fold axis. To confirm whether the low-temperature phase maintains a kagome-like network structure or not, we estimate the overlap integrals between the singly occupied molecular orbital wave functions of the MPYNN molecules by the extended Huckel method. The result is that all the overlap integrals are modified below T-s, suggesting that the system below T-s cannot be regarded as the uniform S = 1 kagome antiferromagnet.

DOI： 10.1143/JPSJ.73.796

Structural phase transition of theta-(BEDT-TTF)(2)RbZn(SCN)(4) under high pressure 査読

M Watanabe, Y Noda, Y Nogami, H Mori

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 4 ) 921 - 925 2004年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

theta-(BEDT-TTF)(2)RbZn(SCN)(4) is known as a two-dimensional organic conductor exhibiting a metal-insulator phase transition associated with a charge ordering phenomena at T-MI = 200 K under ambient pressure. The transition temperature increases with applied pressure and reaches room temperature at 1.1 GPa. The structural change by pressure induced phase transition was investigated by X-ray diffraction using synchrotron radiation. A superlattice formation of 2c was found above 1.1 GPa. A single crystal structural analysis taking account of the superlattice was carried out at 1.2 GPa. Displacements of BEDT-TTF molecules were found to be similar to the displacements in the low temperature phase at the ambient pressure. However, the shrinkage of the c-axis under pressure was four times as large as that under cooling at the transition point. Decreases in the intermolecular distances between BEDT-TTF molecules resulted in increases of the intersite Coulomb energies V and an increase of the electric bandwidth W. U/W (U: on-site Coulomb energy) decreased as a result of an increase of W. Such a change of U/W is obstructive to the enhancement of the charge ordered phase. This indicates that an effect of V is indispensable to the charge-ordered phase in this material.

DOI： 10.1143/JPSJ.73.921

Transfer integrals and the spatial pattern of charge ordering in theta-(BEDT-TTF)(2)RbZn(SCN)(4) at 90 K 査読

M Watanabe, Y Noda, Y Nogami, H Mori

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 73 ( 1 ) 116 - 122 2004年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

theta-(BEDT-TTF)(2)RbZn(SCN)(4) is a two-dimensional organic conductor exhibiting a metal-insulator transition at T-MI = 200 K. This insulating charge ordered state below T-MI was investigated by a single crystal structural analysis taking account of the superlattice formation below T-MI. A large displacement (about 0.2 Angstrom) of BEDT-TTF molecules associated with the transition was found. Transfer integrals between BEDT-TTF molecules were also calculated from the structural data. The two-dimensional net of transfer integrals above T-MI was modulated into the quasi one-dimensional transfer integral chain by the superlattice formation below T-MI. The ionicities of BEDT-TTF molecules are estimated from the intramolecular bond length distribution. As a result, charge disproportionation between BEDT-TTF molecules was found, and the ionicity was 0 to +0.2 and +0.8 to +1.0 respectively. The hole-rich sites are laid on the quasi one-dimensional transfer integral chain. We conclude that the spatial pattern of charge ordering is a stripe alternating along the c-axis.

DOI： 10.1143/JPSJ.73.116

X-ray study of modulated structures of beta '-CuxV2O5 (x=0.29,0.39) 査読

N Nagao, Y Nogami, K Oshima, H Yamada, Y Ueda

PHYSICA B-CONDENSED MATTER 329 713 - 714 2003年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

High resolution X-ray study reveals the wave vector change in the modulated structure of the quasi-one-dimensional compound beta'-Cu vanadium bronze. Structural modulation of the reduced wave vector q(0) = (0, 0.305, 0) emerges below 220 K in beta'-Cu0.29V2O5. For beta'-Cu0.39V2O5, not the single q modulation but two kinds of modulations were observed. A three-fold superlattice structure with q(1) = (0, 0.333, 0) appears below 210 K. An incommensurate modulated structure with q(2) = (0, 0.26-0.29, 0) coexists below 175 K, whose satellite intensity and b* component Q(b) have temperature and passing-time dependencies between 140 and 175 K. The competition between q(1) and q(2) modulations was also observed. It seems that the q(2) is deeply related to the physical property change between 140 and 180 K confirmed by the decrease in the magnetic susceptibility and the increase in the resistivity. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(02)02021-5

High field Fermi surfaces studied by AMRO in eta-Mo4O11 査読

K Oshima, T Kambe, Y Nogami, T Sasaki

PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 18 ( 1-3 ) 198 - 199 2003年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The high field Fermi surface in eta-Mo4O11 at low temperatures has been studied by the Angle-dependent Magnetoresistance Oscillation (AMMO) method (Organic Super Conductors, Springer, Berlin, 1998, p. 455). The Shubnikov-de Haas (SdH) oscillation so far obtained shows existence of the several closed surfaces, but the results only give the area of the pockets. The AMMO result at high fields in the plane perpendicular to the crystal b-axis shows the angle-dependent resistance oscillation together with the SdH oscillations. We see no clear AMMO for the fields in the plane perpendicular to the c-axis. The results indicate the existence of very anisotropic Fermi surfaces, which are expected from the Fermi surface model (Chem. Rev. 91 (1991) 965) taking into account the lower temperature CDW nesting vector q(2). (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S1386-9477(02)00964-5

Effects of tungsten doping on the CDW states of eta-Mo4O11 査読

T Kambe, S Tsuboi, N Nagao, Y Nogami, K Oshima

PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 18 ( 1-3 ) 196 - 197 2003年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The eta-Mo4O11 system shows successive CDW transitions due to its two-dimensional Fermi surface instability. We find that the lower temperature CDW-II transition easily disappears by doping a small amount of W atoms (less than 0.2%/Mo), though the higher temperature CDW-I transition is weakly depressed. The W atoms possibly substitute both the intra- and the inter-layer Mo sites. The doping effectively reduce the carrier compensation, leading to the suppression of TCDW-I. Moreover, the interlayer coherence between the intralayer two-dimensional CDWs may be destroyed by the substitution between the layers since the modulation of CDW-II state has an interlayer component. The resistivity along the conducting plane follows "log T" dependence below 10 K, suggesting that the W atoms doped within the layer should induce the Anderson-type charge localization. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S1386-9477(02)00963-3

Shubnikov-de Haas oscillations and Fermi surface of tau-phase conductors 査読

T Konoike, K Iwashita, Nakano, I, H Yoshino, T Sasaki, Y Nogami, JS Brooks, D Graf, CH Mielke, GC Papavassiliou, K Murata

PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 18 ( 1-3 ) 188 - 189 2003年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

tau-phase organic quasi-two-dimensional conductors have a 4-fold single Fermi surface (FS) from band calculation. At low temperature, the resistivity turns into semiconducting, whereas Shubnikov-de Haas oscillations (SdH) have been observed. The SdH signal includes two frequencies that are inconsistent with the band calculation. Recently, we found the superstructure of this salt below 245 K by X-ray study. This result may explain the contradiction between observation and calculation for the FS. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S1386-9477(02)01004-4

X-ray study of modulated structures of beta '-CuxV2O5 (x=0.29,0.39)

N Nagao, Y Nogami, K Oshima, H Yamada, Y Ueda

PHYSICA B-CONDENSED MATTER 329 ( 329 ) 713 - 714 2003年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

High resolution X-ray study reveals the wave vector change in the modulated structure of the quasi-one-dimensional compound beta'-Cu vanadium bronze. Structural modulation of the reduced wave vector q(0) = (0, 0.305, 0) emerges below 220 K in beta'-Cu0.29V2O5. For beta'-Cu0.39V2O5, not the single q modulation but two kinds of modulations were observed. A three-fold superlattice structure with q(1) = (0, 0.333, 0) appears below 210 K. An incommensurate modulated structure with q(2) = (0, 0.26-0.29, 0) coexists below 175 K, whose satellite intensity and b* component Q(b) have temperature and passing-time dependencies between 140 and 175 K. The competition between q(1) and q(2) modulations was also observed. It seems that the q(2) is deeply related to the physical property change between 140 and 180 K confirmed by the decrease in the magnetic susceptibility and the increase in the resistivity. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(02)02021-5

Shubnikov-de Haas oscillations and low temperature electronic structure in tau-phase conductors 査読

T Konoike, K Iwashita, Nakano, I, H Yoshino, T Sasaki, T Takahashi, Y Nogami, JS Brooks, D Graf, CH Mielke, GC Papavassiliou, K Murata

SYNTHETIC METALS 135 ( 1-3 ) 615 - 616 2003年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

tau-phase organic quasi-two-dimensional conductors have a 4-fold single Fermi surface (FS) from band calculation. At low temperature, the resistivity turns into semiconducting, whereas Shubnikov-de Haas oscillations have been observed. The amplitude of the oscillation is quite large because the system is near the quantum limit (N=2-state) under -27 T. The observed oscillations include two frequencies that are inconsistent with the band calculation. The reason of this discrepancy may be explained by the reconstruction of the FS. In this work, we examined very high magnetic field transport property up to 60 T and reconsider the low temperature crystal structure of this salt by diffuse X-ray study.

DOI： 10.1016/S0379-6779(02)00797-X

Superlattice structural analysis of (TTM-TTP)I-3 at low temperatures 査読

Y Nogami, T Kambe, N Fujimura, K Oshima, T Mori, T Kawamoto

SYNTHETIC METALS 135 ( 1-3 ) 637 - 638 2003年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

The title quasi one-dimensional conductor with a half-filled energy band shows two kinds of modulated structures q(1) of (0 0 0.5) below 160 K and q(2) of (0.5 0 0.5) below 100 K. These wave vectors can nest Q1D Fermi surface. Two kinds of superlattice structures were solved using X-ray. In both cases, enhanced displacements of I-3 ions were observed. Their possible origins and their effects on the physical properties were discussed.

DOI： 10.1016/S0379-6779(02)00755-5

Investigation of X-ray diffuse scattering in theta-(BEDT-TTF)(2)RbM '(SCN)(4) 査読

M Watanabe, Y Noda, Y Nogami, H Mori

SYNTHETIC METALS 135 ( 1-3 ) 665 - 666 2003年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

The modulated structure of theta-(BEDT-TTF)(2)RbM'(SCN)(4); (M'=Zn, Co) were investigated by X-ray diffraction method. theta-(BEDTTTF)(2)RbM'(SCN)(4) are two-dimensional organic conductors which exhibit metal-insulator transition at 210 K. The insulating phase is known as a charge ordered state. Above T-MI = 210 K, diffuse rod of q=(1/3 k 1/4) was found. Below T-MI, there are some differences depending on the sample cooling speed. In the slow-cooled-state (0.2 K/min), the diffuse rod of q=(1/3 k 1/4) disappears and is replaced by superlattice of c*/2. In the rapid-cooled-state (5-6 K/min), the structural phase transition at T-MI becomes imperfect. The diffuse rod of q remains below T-MI and the lattice modulation of c*/2 is disordered in the direction of inter-conducting-layer.

DOI： 10.1016/S0379-6779(02)00769-5

Fermi surface and low temperature structure in (DMET-TSeF)(2)Au(CN)(2) 査読

K Kato, K Oshima, T Kambe, Y Nogami, T Sasaki, M Motokawa, R Kato

SYNTHETIC METALS 135 ( 1-3 ) 577 - 578 2003年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

The title compound is one of the DMET-TSeF salts which are quasi-one-dimensional organic metals at room temperatures. We show that the compound has a closed Fermi surface using the angle-dependent magnetoresistance oscillation (AMRO) method together with magnetoresistance and magnetization quantum oscillation measurements at low temperatures. By the X-ray measurement, we confirm that the structural phase transition observed around 180 K is related to the anomaly observed in the temperature dependence of the resistivity [1]. The nesting vector has the direction of 0.5a*+0.5c*. The obtained low temperature closed Fermi surface has about 4 % of the first Brillouin zone area. The AMRO data show the existence of a very anisotropic Fermi surface where the diameter perpendicular to the most conducting a direction is about 0.5 c*. The possible origin of the low temperature closed Fermi surface is discussed and the relation to the ordering of anion molecules is considered as the probable reason.

DOI： 10.1016/S0379-6779(02)00738-5

Magnetic investigation of itinerant and local hybrid spins system, (CHTM-TTP)(2)TCNQ 査読

T Nakamura, M Taniguchi, Y Misaki, K Tanaka, Y Nogami

SYNTHETIC METALS 133 441 - 442 2003年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

EPR measurements of a new two-component organic conductor, (CHTM-TTP)(2)TCNQ, were performed. This salt shows two drastic successive phase transitions at low temperatures. The electronic phases of the title salt are discussed by microscopic point of view. The contributions of the two-spin species of the magnetic properties are separated. Possibility of cooperative phenomena in the two-spin system with itinerant and localised moments is discussed. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00274-6

Magnetic properties of TDAE-C-70-toluene 査読

K Oshima, T Kambe, M Fujiwara, Y Nogami

SYNTHETIC METALS 133 699 - 701 2003年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

The magnetic properties of single crystal TDAE-C-70-toluene are reported in relation to its unique dimerized structure Of C-70 molecules in the unit cell. The g-factor at room temperature (g = 2.0052) suggests that the origin of the magnetism is different from C-70 (g = 2.002). The spins on the C-70 molecules are cancelled out due to the dimerization. No magnetic phase transition appears at least down to 0.5 K. The magnetic susceptibility follows the Curie-Weiss law with the Weiss constant of +0.36 K. These results show that the weakly coupled spins on TDAE molecules contribute the magnetism of this salt, which is in contrast to the ferromagnetic TDAE-C-60 where the TDAE spins are cancelled. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00430-7

Structural phase transition in theta-(BEDT-TTF)(2)RbM '(SCN)(4) (M ' = Zn, Co) 査読

M Watanabe, Y Noda, Y Nogami, H Mori, S Tanaka

SYNTHETIC METALS 133 283 - 285 2003年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

Spatial pattern of charge ordering in two-dimensional compound theta-(BEDT-TTF)(2)RbM'(SCN)(4) (M' = Zn, Co) was revealed using single crystal X-ray structural analysis below the metal-insulator transition temperature T-c of around 190 K. Molecular ionicity was evaluated by the intramolecular bond length. The ordering pattern of charge disproportion among ET molecules was stripe ordered alternating c-axis (horizontal stripe). (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00311-9

The charge ordered state and the possible 2k(F)-CDW state with Fermi surface nesting in organic conductor 0-(BEDT-TTF)(2)MM'(SCN)(4) (MM '= RbZn, CsCo) 査読

M Watanabe, Y Noda, Y Nogami, K Oshima, H Mori

JOURNAL DE PHYSIQUE IV 12 ( PR9 ) 231 - 232 2002年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：E D P SCIENCES

Two-dmensional organic conductor theta-(BEDT-TTF)(2)RbZn(SCN)(4) and theta-(BEDT-TTF)(2)CsCo(SCN)(4) were investigated by X-ray diffraction measurements. Both salts exhibit an isostructural crystal structure at room temperature (RT). However, the RbZn salt undergoes a metal-insulator transition associated with superlattice formation of 2c. The charge ordered state below T-Ml, was observed by crystal structure analysis taking into account of the superlattice. This modulation of 2c has no relation to the topology of the calculated Fermi surface nesting vector at all. Below T-Ml, the systematic deformations of BEDT-TTF molecular shape indicated charge disproportionation between BEDT-TTFs possibly caused by the electron correlation effect. On the other hand, in the CsCo salt, another incommensurate lattice modulation was found under high pressure of 1GPa. This incommensurate modulation vector of (2/3 0 0.29) is in agreement with the nesting vector of Fermi surface under high pressure. In this system, it seems that small change caused by chemical substitution can vary the electronic state from the charge ordered state to the CDW state.

DOI： 10.1051/jp4:20020401

Unusual 2k(F) CDW state with enhanced charge ordering in beta-(BEDT-TTF)(2)AsF6 and PF6 査読

Y Nogami, T Mori

JOURNAL DE PHYSIQUE IV 12 ( PR9 ) 233 - 234 2002年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：E D P SCIENCES

X-ray superstructure analyses of the 2k(F) CDW states for two-dimensional organic compounds beta-(BEDT-TTF)(2)PF6 and AsF6 were presented Molecular ionicity of BEDT-TFF was evaluated with both intramolecular bond lengths and molecular shape. Strong bending of quasi-neutral BEDT-TTF molecules coupled with the enhanced amplitude of charge modulation was observed Conformational ordering of the terminal ethylenes of BEDT-TTF molecules and dimerization between quasi-ionic BEDT-TTF molecules were also observed These characteristic indicates this CDW is not Peierls-Frohlich type but coupled with the internal degree of the molecular shape and possibly the intersite Coulomb repulsion.

DOI： 10.1051/jp4:20020402

X-ray observation of 2k(F) and 4k(F) charge orderings in (TMTTF)(2)ReO4 and (TMTTF)(2)SCN associated with anion orderings 査読

Y Nogami, T Nakamura

JOURNAL DE PHYSIQUE IV 12 ( PR9 ) 145 - 148 2002年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：E D P SCIENCES

Electronic transfer integrals (t) and TMTTF molecular ionicities (rho) in several Fabre salts were estimated using the atomic coordinates obtained by systematic X-ray structure analyses at room and low temperatures. Among these Fabre salts containing the octahedral anions, (TMTTF)(2)PF6 has the largest degree of 4k(F) bond dimerization in t, (TMTTF)(2)AsF6 does the middle and (TMTTF)(2)SbF6 has the smallest. This tendency corresponds well to the degree of 2k(F) spin-Peierls instability at low temperatures which had been estimated. However opposite tendency was observed between the magnitude of the 4kF bond dimerization and the reported critical temperature of the charge disproportionation. The charge modulation patterns and the transfer integral modulation patterns of two salts containing non centrosymmetric anions, (TMTTF)(2)ReO4 and (TMTTF)(2)SCN were compared.

DOI： 10.1051/jp4:20020381

Microscopic investigation of a new two-component organic conductor with itinerant and localized spins: (CHTM-TTP)(2)TCNQ 査読

T Nakamura, M Taniguchi, Y Misaki, K Tanaka, Y Nogami

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 71 ( 9 ) 2208 - 2215 2002年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

Low-temperature electronic phases in a new two-component organic conductor, a segregated-stack charge-transfer salt called (CHTM-TTP)(2)TCNQ, are investigated. The ESR g tensor analyses indicate that there exist itinerant CHTM-TTP spins and localized TCNQ spins at R.T. The temperature dependence of the physical parameters reveals that this salt undergoes two drastic, successive phase transitions at low temperatures. The effective moment of the localized TCNQ spins decreases at the 245 K transition and completely disappears at the transition around 195 K. These curious physical properties are explained by the drastic changes in the electronic states of the two different types of spins. The spin susceptibility was decomposed into the contribution of each of the two spin species by using ESR, H-1-NMR, and static susceptibility analyses. We present a microscopic investigation of the two-spin system with itinerant and localized moments.

DOI： 10.1143/JPSJ.71.2208

ESR investigation of organic conductor with itinerant and local spins, (CHTM-TTP)(2)TCNQ 査読

T Nakamura, M Taniguchi, Y Misaki, K Tanaka, Y Nogami

EPR IN THE 21ST CENTURY: BASICS AND APPLICATIONS TO MATERIAL, LIFE AND EARTH SCIENCES 192 - 196 2002年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：ELSEVIER SCIENCE BV

ESR investigation was carried out for the organic conductor with itinerant and local spins, (CHTM-TTP)(2)TCNQ. This salt shows two drastic successive phase transitions at low temperatures. The contributions of the two spin species of the magnetic properties are separated using with the g-tensor analyses. The electronic phases of the title salt are discussed by microscopic point of view.

DOI： 10.1016/B978-044450973-4/50035-4

Low temperature X-ray and ESR study of Quasi-1D DMTCA-BF4 (C = S, Se) with half-filled band 査読

T Kambe, N Fujimura, Y Nogami, K Oshima, K Yakushi, J Dong, K Takimiya, T Otsubo

SYNTHETIC METALS 120 ( 1-3 ) 931 - 932 2001年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

DMTCA-BF4 (C = S, Se) have been considered as a quasi-one-dimensional half-filled system. For both salts, the structural two-fold modulation along the stacking direction was observed from room temperature. We also found a rapid decrease in spin susceptibility of DMTSA-BF4 below 100 K, but no anomaly at the metal-insulator transition temperature (150 K).

DOI： 10.1016/S0379-6779(00)01126-7

Two incommensurate CDWs in low-dimensional conductor eta-Mo4O11 査読

Y Nogami, T Kambe, N Nagao, K Oshima

SYNTHETIC METALS 120 ( 1-3 ) 1049 - 1050 2001年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

Using X-ray camera and diffractometer, structural evidence of the second CDW transition for the quasi two-dimensional conductor eta -Mo4O11 was presented. CDW critical wave vectors have been determined with high precision. Extremely weak satellite reflections at the reduced wave vector q(2)=(0.552 0.47 0.30) emerge below 25 K. Satellite reflections at the reduced wave vector q(1) = (0 0.232 0) was observed below 105 K.

DOI： 10.1016/S0379-6779(00)01192-9

The structural and magnetic properties in TDAE-fullerene system 査読

K Oshima, Y Nogami, T Kambe, N Nagao, M Fujiwara

NANONETWORK MATERIALS: FULLERENES, NANOTUBES AND RELATED SYSTEMS 590 393 - 396 2001年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：AMER INST PHYSICS

The structural and magnetic properties are discussed on the TDAE-fullerene system for C-60 and C-70. The single crystal structural analysis reveals that the TDAE-C-70 system contains solvent molecules (toluene), and the C-70 molecules in the unit cell axe dimerized. The room temperature structure is monoclinic P2(1)/n, and crystal parameters are a=18.82(3)Angstrom, b=16.38(2)Angstrom, c=18.73(3)Angstrom and beta = 117.58(5)degrees. The same annealing procedure used in TDAE-C-60 does not alter the magnetic behavior in TDAE-C-70. A preliminary report is given for the TDAE-C-60 structural study in magnetic fields up to 7 T. The possible method that directly reveals the relation between magnetism and the molecular arrangement is proposed.

Annealing effects on the magnetic and structural properties of single-crystal TDAE-C-60 査読

T Kambe, Y Nogami, K Oshima

PHYSICAL REVIEW B 61 ( 2 ) R862 - R865 2000年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Annealing effects on the magnetic and structural properties of single-crystal TDAE-C-60 are investigated. When a crystal is well-annealed at 350 K, ferromagnetic ordering takes place below 16 K, though no magnetic phase transition is shown in as-grown crystal. The saturated magnetization was obtained to be 0.9+/-0.1 mu(B) per C-60. It was first found that the well-annealed crystal shows a structural phase transition around 180 K, probably associated with the orientational ordering of C-60 molecules. On the other hand, the as-grown crystal undergoes no structural phase transition at least down to 30 K while the motion of C-60 molecules is restricted below around 150 K. The possible relation between the low-temperature structure and the magnetic ordering is discussed.

DOI： 10.1103/PhysRevB.61.R862

X-ray structural study of 4k(F) Wigner crystal and 4k(F) Peierls state in DCNQI complex with 1/4 filled quasi one-dimensional band 査読

Y Nogami, K Oshima, K Hiraki, K Kanoda

JOURNAL DE PHYSIQUE IV 9 ( P10 ) 357 - 359 1999年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：E D P SCIENCES

Using newly developed X-ray low temperature came-a 4k(F) periodic modulation was observed in organic quasi one-dimensional(Q1D) compounds (DMe-DCNQI)(2)Ag(abbreviated as DMe) and(DI-DCNQI)(2)Ag (abbreviated as DI). From 4k(F) satellite reflection intensity distribution in q-space, periodic molecular displacement in DMe and periodic molecular deformation possibly related with molecular valence ordering in DI were found. These modulation patterns suggest occurrence of 4k(F) bond CDW in DM and 4k(F) site CDW in DI. The 4k(F) site CDW possibly caused by a marked intersite correlation V,can be interpreted as a Wigner crystal.

DOI： 10.1051/jp4:19991095

Novel pressure-induced 2k(F) CDW state in organic low-dimensional compound theta-(BEDT-TTF)(2)CsCo(SCN)(4) 査読

M Watanabe, Y Nogami, K Oshima, H Mori, S Tanaka

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 68 ( 8 ) 2654 - 2663 1999年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOCIETY JAPAN

A band structure calculation based on the X-ray structure analysis reveals that pressure raises quasi one-dimensionality of the Fermi surface of the title compound. A 2k(F) lattice modulation is observed with a wave vector q(3)' = (2/3 0 0.29) at 10.7 kbar and room temperature. This is the first observation of pressure-induced CDW. With cooling, the wave vector of the modulation changes from q(3)' to commensurate q(3) = (2/3 0 1/3) below 240 K. On the other hand, at ambient pressure and 20 K where the resistivity begins to increase rapidly, three-dimensional short range ordering occurs for the weak diffuse spot with a wave vector q(2) = (0 0 1/2), This modulation is ascribable to an occurrence of charge ordering possibly caused by the nearest neighbor Coulomb interaction V. A schematic phase diagram for the electronic state is presented.

DOI： 10.1143/JPSJ.68.2654

Annealing effects on organic ferromagnet C-60-TDAE 査読

T Kambe, H Negawa, Y Nogami, K Oshima

SYNTHETIC METALS 103 ( 1-3 ) 2424 - 2424 1999年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

The annealing effects on the magnetic and structural properties for organic ferromagnet C-60 - TDAE are reported. The ESR line-width for unannealed single crystal shows a large hysteresis behavior around 130K. For the well-annealed crystal, on the other hand, the linewidth continuously changed with temperature. In addition, the room temperature structural analysis of the single crystal indicated that all the crystal axes, especially c-axis, shrunk after annealing.

DOI： 10.1016/S0379-6779(98)00702-4

Soliton dynamics in TTF-CA 査読

T Kambe, Y Nogami, K Oshima, Y Takashi, H Sakai, S Koshihara

SYNTHETIC METALS 103 ( 1-3 ) 1824 - 1824 1999年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

Electron Spin-Echo (ESE) measurements on mixed-stack charge transfer compound tetrathiafulvalene (TTP)-chloranil (CA) are reported. Below Neutral-Ionic transition temperature, the ESE signals related to the spin solitons were observed. Comparing the phase memory time with the inverse of the EPR line-width, it was found that a crossover from fast motion of the spin solitons to slow motion took place around 70K. In addition ,the spin relaxation measurements suggested the thermal fluctuation of the dimerized lattice above 60K.

DOI： 10.1016/S0379-6779(98)00472-X

Low Temperature X-Ray and ESR study of one-dimensional compound (TTM-TTP)I-3 査読

N Fujimura, A Namba, T Kambe, Y Nogami, K Oshima, T Mori, T Kawamoto, Y Misaki, T Yamabe

SYNTHETIC METALS 103 ( 1-3 ) 2111 - 2112 1999年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

(TTM-TTP)I-3 which has been considered as the typical one-dimensional half-filled band system, has been critically restudied by structural and magnetic measurements. X-ray diffuse scattering study reveals the formation of 2k(F) CDW superstructure with the wave vector q(1) =(0, 0, 0.5) below 160 K of the metal-insulator transition temperature. Another structural modulation with q(2) = (0.5, 0, 0.5) is observed below 90-100 K. modulated structure analysis using the q(2) satellite reflections and the Bragg reflections shows the large displacement in I-3 anion. Anomalies in chi line width and g-value of ESR measurements which correspond to the structural anomaly, are also reported.

DOI： 10.1016/S0379-6779(98)00473-1

Low temperature superstructure and transfer integrals in kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]X : X = Cl, Br 査読

M Watanabe, Y Nogami, K Oshima, H Ito, T Ishiguro, G Saito

SYNTHETIC METALS 103 ( 1-3 ) 1909 - 1910 1999年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

Low temperature crystal structures and band parameters were presented for the deuterized (d) and the hydrogenized (h) kappa - (BEDT-TTF)2Cu[N(CN)2]Cl and for deuterized kappa-(BEDT-TTF)2Cu[N(CN)2]Br. An enhanced molecular dimerization was observed for the Cl salts. Theoretical prediction by H. Kino and H. Fukuyama that the molecular dimerization stabilizes the Mott insulating state was confirmed. Below 200 K, X-ray diffuse scattering study revealed formation of two dimensional ax2c superstructure in the deuterized kappa -(BEDT-TTF)2CU[N(CN)2]Br. The structural disorder for the d-Br salt was observed in the superstructure and in the terminal ethylenes.

DOI： 10.1016/S0379-6779(98)00615-8

X-ray structural study of 4k(F) superlattice in (DIDCNQI)(2)Ag 査読

Y Nogami, R Moret, JP Pouget, Y Yamamoto, K Oshima, K Hiraki, K Kanoda

SYNTHETIC METALS 102 ( 1-3 ) 1778 - 1778 1999年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

X-ray diffuse scattering study using monochromatic camera revealed c*/2 satellite; reflections, indicating three dimensional 4k(F) CDW formation in quasi one-dimensional compound (DIDCNQI)(2)Ag below 200 K.

DOI： 10.1016/S0379-6779(98)00612-2

Structural modulation in theta-(BEDT-TTF)(2)CsM '(SCN)(4)[M '=Co, Zn] 査読

Y Nogami, JP Pouget, M Watanabe, K Oshima, H Mori, S Tanaka, T Mori

SYNTHETIC METALS 103 ( 1-3 ) 1911 - 1911 1999年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

X-ray diffuse scattering study reveals presence of diffuse sheets directed along both the 2a*+c* and 2a*-c* directions in theta-(BEDT-TTF)(2)CsM'(SCN)(4) [M'=Co, Zn] at room temperature. These diffuse streaks condensed into two diffuse rods at the q(1)=(2/3, k, 1/3) and q(2)=(0. k, 1/2) reduced reciprocal position below 120K. Around 50K when the resistivity begins to increase, an enhancement of the q(2) intensity is observed.

DOI： 10.1016/S0379-6779(98)00616-X

High pressure structure of (DIDCNQI)(2)Cu 査読

Nogami Y, Yamamoto Y, Hayashi S, Oshima K, Hiraki H, Kanoda K

SYNTHETIC METALS 103 ( 1-3 ) 2252 1999年6月

低次元有機錯体の低温・高圧下構造測定

野上由夫, 大嶋孝吉

日本結晶学会誌 41 ( 1 ) 48 - 56 1999年2月

記述言語：日本語出版者・発行元：The Crystallographic Society of Japan

Various ground states such as superconductivity, Mott insulator, CDW and charge ordering for low-dimensional organic complexes, are studied using X-ray. Techniques including homemade cameras and know-hows for low temperature and high pressure X-ray measurements are presented.

DOI： 10.5940/jcrsj.41.48

その他リンク： https://jlc.jst.go.jp/DN/JALC/00059771517?from=CiNii

High Pressure Structures of Organic Low Dimensional Conductor DCNQI Compounds 査読

Y. Nogami, S. Hayashi, T. Date, K. Oshima, K. Hiraki, K. Kanoda, K. Hiraki, K. Kanoda

Review of High Pressure Science and Technology/Koatsuryoku No Kagaku To Gijutsu 7 404 - 406 1998年

記述言語：英語掲載種別：研究論文（学術雑誌）

Using X-ray and DAC, room-temperature crystal structures under physical pressure(PP) were solved for DCNQI-Cu compounds which exhibit particular metal-insulator(M-I) transition owing to their electronic low dimensionality(CDW) and strong correlation(Mott). This M-I transition is known to be triggered with moderate(=small) PP or chemical substitution(chemical pressure:CP). Observed high pressure structures were compared with theoretical structure determinations. From the structural viewpoint, relation between PP and CP effects on the M-I transition was discussed, [organic conductor, metal-insulator transition, charge density wave, Mott transition, X-ray diffraction]. © 1998, The Japan Society of High Pressure Science and Technology. All rights reserved.

DOI： 10.4131/jshpreview.7.404

Low temperature structure of the alpha PRIME;-(BEDT-TTF)(2)IBr2 organic magnetic semiconductor 査読

M Watanabe, M Nishikawa, Y Nogami, K Oshima, G Saito

JOURNAL OF THE KOREAN PHYSICAL SOCIETY 31 ( 1 ) 95 - 98 1997年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：KOREAN PHYSICAL SOC

A low temperature structure analysis for the alpha'-(BEDT-TTF)(2)IBr2 compound has been carried out. The temperatures studied include the regions where anomalous behavior of the conductivity and the susceptibility exist. It has been found that particular terminal ethylene groups of the BEDT-TTF molecules in the unit cell show anomalous temperature-dependent behavior. An anomalous behavior of the unit-cell parameter gamma has been also observed. These are considered to be related with the anomaly of the conductivity around 200 K. No remarkable change in unit-cell parameters has been observed corresponding to the change of the susceptibility around 60 K. It is possible to calculate overlap integrals between the BEDT-TTF molecules by using low-temperature crystal data. They show characteristic changes among three temperatures 300, 120, and 20 K.

Low temperature structures of (BEDT-TTF)(3)CuBr4 査読

M Watanabe, Y Nogami, K Oshima, J Yamaura, T Enoki, G Saito

SYNTHETIC METALS 86 ( 1-3 ) 1983 - 1984 1997年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

Single crystal X-ray structure analyses and calculation of overlap integrals for (BEDT-TTF)(3)CuBr4 reveal an occurrence of structural trimerization among BEDT-TTF molecules below Te = 60.2 K. A possible relation between this structural change and the magnetic susceptibility decrement below Tc is discussed.

DOI： 10.1016/S0379-6779(97)80988-5

Single crystal X-ray study of pressure-induced metal-insulator transition in (DMeDCNQI)(2)Cu 査読

Y Nogami, T Date, K Oshima, O Arimoto

SYNTHETIC METALS 86 ( 1-3 ) 2073 - 2074 1997年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

The structures of the metallic and the insulating phases of (DMeDCNQI)(2)CU were solved under pressures of up to 15.8 kbar at room temperature. An angle a representing the deformation of CuN4 tetrahedron around the Cu atom increases almost linearly with pressure at the rate of about 0.6 deg./kbar. Furthermore, an X-ray diffuse scattering study revealed the presence of a 3 c CDW superlattice structure above 12 kbar in the high pressure insulating phase.

DOI： 10.1016/S0379-6779(97)81033-8

Characteristic SDW and FISDW behavior in (DMET-TSeF)(2)X system 査読

K Oshima, H Okuno, H Fujimura, Y Nogami, S Aonuma, R Kato

SYNTHETIC METALS 86 ( 1-3 ) 1965 - 1966 1997年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

The quasi one-dimensional system (DMET-TSeF)2X which is similar to (TMTSF)2X is studied. The remarkable magnetic and transport properties for the salts with X=AuI2, AuBr2 and AuCl2 are shown. It is shown from the magnetic measurement that the AuBr2 salt becomes SDW at ambient pressure and its easy-axis is along the most conducting a-axis. FISDW states has been observed for X=AuCl2 AuI2 at ambient pressure and X=AuBr2 under pressure respectively. Low temperature structural analyses have confirmed no superstructure to exist for the AuI2 and AuCl2 salts. Hall effect measurements have revealed the sign change of the Hall voltage(AuI2) and the plateau-like Hall voltage(AuCl2), but at the higher fields than those reported for TMTSF system.

DOI： 10.1016/S0379-6779(97)80980-0

A new highly conductive BO-(MeO)(2)TCNQ Langmuir-Blodgett film 査読

K Ogasawara, T Ishiguro, S Horiuchi, H Yamochi, G Saito, Y Nogami

SYNTHETIC METALS 86 ( 1-3 ) 1835 - 1836 1997年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

A stable, highly conductive Langmuir-Blodgett (LB) film was developed with a charge-transfer (CT) complex of bisethylenedioxytetrathiafulvalene (BO) and dimethoxytetracyanoquinodimethane using the unique nature of BO molecules. The metallic temperature dependence of electrical conductivity was observed down to 180 K, showing a maximum of 13 S/cm, The X-ray diffraction measurements show the presence of three kinds of domains corresponding to CT complex, icosanoic acid and disordered CT complex regions, The behavior of macroscopic electrical conductivity is understood well by a percolation model consisting of metallic, semiconducting and insulating sites.

DOI： 10.1016/S0379-6779(97)80927-7

Percolation conduction in BO-C(10)TCNQ conductive Langmuir-Blodgett films 査読

K Ogasawara, T Ishiguro, S Horiuchi, H Yamochi, G Saito, Y Nogami

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 58 ( 1 ) 39 - 49 1997年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

The structure and electronic properties of the conductive Langmuir-Blodgett film consisting of bis(ethylenedioxy)tetrathiafluvalene- decyltetracyanoquinodimethane (BO-C(10)TCNQ) and icosanoic acid (IA) have been studied through the measurements of electrical conductivity, X-ray diffraction and electron spin resonance for samples with different mixing ration of BO-C(10)TCNQ to IA. The X-ray diffraction and ESR measurements indicate the coexistence of metallic, semiconducting and insulating domains. The temperature dependences of the electrical conductivity are reproduced by the calculation based on a modified two-dimensional percolation model consisting of three kinds of sites and their characteristics are understood well by the related phase diagram. Copyright (C) 1996 Elsevier Science Ltd

DOI： 10.1016/S0022-3697(96)00098-4

Structural phase transition in (BEDT-TTF)(3)CuBr4 at 60 K 査読

M Watanabe, Y Nogami, K Oshima, JI Yamaura, T Enoki, G Saito

SOLID STATE COMMUNICATIONS 100 ( 11 ) 755 - 758 1996年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

Low temperature X-ray diffraction study for organic semiconductor (BEDT-TTF)(3)CuBr4 revealed structural phase transition from P2(1)/c to Pc by losing inversion and screw symmetries at 60.2 K where the magnetic susceptibility shows a steep decrease. Abrupt changes in (0k0) X-ray reflection intensity and lattice parameters proved that this phase transition has first-order nature. Structure analysis at 65.9 K verified that the average coordination number of Br around Cu is four. Copyright (C) 1996 Elsevier Science Ltd

DOI： 10.1016/S0038-1098(96)00512-1

Structural study of the highly conductive tridecylmethylammonium-Au(dmit)(2) Langmuir-Blodgett films 査読

H Matsuzaki, K Ogasawara, T Ishiguro, Y Nogami, M Taoda, H Tachibana, M Matsumoto, T Nakamura

SYNTHETIC METALS 74 ( 3 ) 251 - 255 1995年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

The structure of the conductive Langmuir-Blodgett (LB) film consisting of tridecylmethylammonium-Au(dmit)(2) (3C10-Au) and arachidic acid is studied by the X-ray diffraction method and atomic force microscopy (AFM). The electrochemically ClO4--doped film is found to possess four phases with different interlayer spacings by the X-ray diffraction method. The intralayer molecular arrangement is found for the 3C10-Au matrix by AFM.

DOI： 10.1016/0379-6779(95)03376-U

STRUCTURAL STUDY OF NEUTRAL-IONIC TRANSITION IN DMTTF-CA 査読

Y NOGAMI, M TAODA, K OSHIMA, S AOKI, T NAKAYAMA, A MIURA

SYNTHETIC METALS 70 ( 1-3 ) 1219 - 1220 1995年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

Dimethyltetrathiafulvalene-p-chloranil (DMTTF-CA), showing a particular neutral(N)-ionic(I) transition from a N phase into a N-I coexisting phase by cooling, was structural analyzed by X-ray at 29K, 48K, 109K and 293K Below Tc or 65K, changes observed in unit cell parameters, bond lengths and anisotropic temperature factors indicate 1) a increase in degree of charge transfer(CT) from a DMTTF donor to a CA acceptor and 2) a formation of a molecular dimerization, in I part of the coexisting phase. A possible staging superlattice was not observed.

TEMPERATURE-DEPENDENCE OF LOCAL-STRUCTURE OF RB3C60 SUPERCONDUCTOR 査読

T FUJIMOTO, Y KUBOZONO, H MAEDA, S EMURA, H ISHIDA, K OSHIMA, K KATO, S KASHINO, H YAMAZAKI, T ISHII, Y NOGAMI

FULLERENE SCIENCE AND TECHNOLOGY 3 ( 1 ) 69 - 77 1995年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：MARCEL DEKKER INC

EXAFS studies on Rb3C60 are made as a function of temperature from 6 K to 300 K. It is found that the distance r(Rb-C) and the second, third and fourth cumulant terms of Debye-Waller factors, sigma(2), sigma(c)(3) and sigma(c)(4), show the anomalous behavior near T-c.

DOI： 10.1080/153638X9508545734

LOCAL-STRUCTURE OF METAL-IONS IN ARACHIDATE LANGMUIR-BLODGETT-FILM 査読

S TAKEUCHI, Y NOGAMI, T ISHIGURO, H OYANAGI

THIN SOLID FILMS 250 ( 1-2 ) 243 - 248 1994年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

The fluorescence extended X-ray absorption fine structures near the Ba-L(3) edge of a Ba-arachidate (CH3(CH2)(18)COO2Ba) Langmuir-Blodgett film are investigated by using polarized X-rays from a synchrotron radiation source. From the analysis of the observed spectra for different incident angles, the absorption-site geometries are obtained. The distance from the Ba ion to the nearest neighbor oxygen atoms, lying almost in the Ba plane, is found to be 0.278 nm. Taking account of the reported structural data, a local structure model around the Ba ion is proposed.

RECENT STRUCTURAL INVESTIGATIONS OF METALLIC POLYMERS 査読

JP POUGET, Z OBLAKOWSKI, Y NOGAMI, PA ALBOUY, M LARIDJANI, EJ OH, Y MIN, AG MACDIARMID, J TSUKAMOTO, T ISHIGURO, AJ EPSTEIN

SYNTHETIC METALS 65 ( 2-3 ) 131 - 140 1994年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

Recent structural studies of the undoped and iodine-doped polyacetylenes (prepared by the Tsukamoto and co-workers method), PF6--doped polypyrrole and polyaniline emeraldine base and (hydrochloric acid and camphorsulfonic acid) salts are presented. Some key features of the polymer chain array and its evolution with the conditions of preparation are emphasized. Special attention has been devoted to characterization of the various sources of structural disorder in the relationship with high conductivity and related properties exhibited by these three families of polymers. Variation in the structural order in both crystalline and amorphous regions correlates directly with the electrical and optical properties of the metallic state.

DOI： 10.1016/0379-6779(94)90174-0

LOW-TEMPERATURE MAGNETORESISTANCE OF HIGHLY CONDUCTIVE POLYACETYLENE 査読

H KANEKO, Y NOGAMI, T ISHIGURO

PHYSICA B 194 1327 - 1328 1994年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Low temperature resistivity of highly conductive iodine-doped polyacetylene changes systematically from metallic to nonmetallic with increase of disorder. The negative magnetoresistance in metallic region is ascribed to the effect of weak localization. Meanwhile the positive magnetoresistance found in nonmetallic region is explained by magnetic field effect to variable range hopping among localized states in a quasi 1D electron gas.

DOI： 10.1016/0921-4526(94)90993-8

OBSERVATION OF PHONON STOP BAND IN LANGMUIR-BLODGETT MULTILAYER FILM 査読

S TAKEUCHI, Y NOGAMI, T ISHIGURO

PHYSICA B 194 473 - 474 1994年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Using superconducting tunnel junctions, phonon transmission for Langmuir-Blodgett (LB) multilayer has been studied spectroscopically. A film with 9 layers of Cd arachidate is formed on a sapphire substrate which passes longitudinal phonon as focusing mode. We find a pronounced decrease in transmission centering 420 GHz corresponding to phonon stop band.

DOI： 10.1016/0921-4526(94)90566-5

STRUCTURE OF HIGHLY CONDUCTING PF6--DOPED POLYPYRROLE 査読

Y NOGAMI, JP POUGET, T ISHIGURO

SYNTHETIC METALS 62 ( 3 ) 257 - 263 1994年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

The structure of highly conducting PF6--doped polypyrrole, the room-temperature conductivity of which is approximately 1500 S/cm, is studied using X-ray 'monochromatic' Laue photographic methods. The 'crystalline' domain size along the polymer chain is estimated to be less than 20 angstrom, while adjacent chains are rather well ordered with spacing of 3.4 angstrom, suggesting that the system can be of two-dimensional nature. The influence of the structural properties on the high electrical conductivity is discussed.

SUPERLATTICE STRUCTURAL TRANSITION IN THE ORGANIC SUPERCONDUCTOR KAPPA-(BEDT-TTF)(2)CU[N(CN)(2)]BR 査読

Y NOGAMI, JP POUGET, H ITO, T ISHIGURO, G SAITO

SOLID STATE COMMUNICATIONS 89 ( 2 ) 113 - 116 1994年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

By the X-ray ''monochromatic'' Laue photographic method, we observe the formation below 200 K of superlattice reflections in k-(BEDT-TTF)(2)Cu[N(CN)(2)]Br which exhibits the highest superconducting critical temperature at ambient pressure (T-c similar to 11.6 K) among the organic superconductors. This displacive structural transition doubles the lattice parameter along c. We discuss the driving force of this instability and the consequences of this structural transition on the electronic and lattice properties of this salt.

低次元物質の相転移

野上由夫

日本結晶学会誌 36 ( 0 ) 17 - 18 1994年

HIGH-RESOLUTION X-RAY STUDY ON ANOMALOUS DIFFRACTION PEAK SHIFT IN DIMERIZED LANGMUIR-BLODGETT SUPERLATTICE FILMS 査読

Y NOGAMI, K OGASAWARA, S TAKEUCHI, T ISHIGURO, T NAKAJIMA, K OHSUMI, Y SHIMIZUGAWA

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 62 ( 9 ) 3114 - 3126 1993年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

Structures of Langmuir-Blodgett (LB) superlattice films formed with alternately deposited fatty acid Cd salts with different alkyl-chain length are studied by high resolution X-ray diffraction method using a synchrotron radiation source. The remarkable diffraction peak shift is observed in the superlattice film. The shift is interpreted in terms of the Guinier effect in partially-disordered superlattice system. Simultaneous modulation of molecular position and of molecular scattering factor results in the peak shift. The effect of alkyl-chain species substitution and of cooling on the peak shift are also described. The partial disorder in the superlattice is caused by dissolution of LB film.

LOW-TEMPERATURE ELECTRICAL-CONDUCTIVITY OF HIGHLY CONDUCTING IODINE-DOPED POLYACETYLENE 査読

H KANEKO, Y NOGAMI, T ISHIGURO, H NISHIYAMA, H ISHIMOTO, A TAKAHASHI, J TSUKAMOTO

SYNTHETIC METALS 57 ( 2-3 ) 4888 - 4893 1993年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

The low temperature electrical conductivities of heavily iodine-doped polyacetylene with different degrees of disorder are reported. The sample with room-temperature conductivity of 1.0 x 10(5) S/cm showed weak temperature dependence below 1 K down to 0.8 mK. With moderate increase of disorder, logarithmic temperature dependence was observed. The results are interpreted in terms of scattering of conduction carriers accompanying change of atomic configurations of equivalent energy in the polymer backbone, after similar process in amorphous metal alloys.

DOI： 10.1016/0379-6779(93)90834-J

HIGH-ELECTRIC-FIELD EFFECT ON THE CONDUCTIVITY OF IODINE-DOPED POLYACETYLENE 査読

Y NOGAMI, M YAMASHITA, H KANEKO, T ISHIGURO, J TSUKAMOTO, A TAKAHASHI

SYNTHETIC METALS 57 ( 2-3 ) 4854 - 4859 1993年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

The conductivities of iodine-doped new polyacetylenes with room-temperature values of 7.7 x 10(3) S/cm and 2.6 x 10(4) S/cm were measured as a function of applied electric field in the temperature range of 77 K to 4.2 K. It is shown that the behavior deviated obviously from the Sheng model which has been widely adopted in explaining temperature dependence for conventional polyacetylene with lower conductivity.

DOI： 10.1016/0379-6779(93)90828-K

NONLINEAR ELECTRICAL-CONDUCTIVITY OF HIGHLY CONDUCTING IODINE-DOPED POLYACETYLENE 査読

Y NOGAMI, M YAMASHITA, H KANEKO, T ISHIGURO, A TAKAHASHI, J TSUKAMOTO

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 62 ( 2 ) 664 - 671 1993年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

Non-ohmic behaviors under high electric field were investigated for highly conducting iodine-doped polyacetylene at different temperatures. The field dependence was enhanced with decrease of measuring temperature and conductivity. Through systematic numerical analysis we show that the high-field characteristics at different temperatures cannot be described consistently by Sheng model which has been utilized for analyzing the temperature dependence of conventional polyacetylene.

LOGARITHMIC TEMPERATURE-DEPENDENCE OF RESISTIVITY IN HEAVILY DOPED CONDUCTING POLYMERS AT LOW-TEMPERATURE 査読

T ISHIGURO, H KANEKO, Y NOGAMI, H ISHIMOTO, H NISHIYAMA, J TSUKAMOTO, A TAKAHASHI, M YAMAURA, T HAGIWARA, K SATO

PHYSICAL REVIEW LETTERS 69 ( 4 ) 660 - 663 1992年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMERICAN PHYSICAL SOC

Electrical resistivities of heavily doped polyacetylene and polypyrrole exhibit a wide range of temperature variation as a function of the degree of disorder. Thermal activation behavior is found for the strongly disordered state, while a weak temperature dependence down to the mK region is found for the weakly disordered state. In the intermediate region we found the resistivity represented by a logT dependence, in a manner similar to amorphous metals. As a cause of the logT dependence, the possibility of scattering via interaction with molecular configurations possessing low-energy internal degrees of freedom is considered.

UNUSUAL X-RAY-DIFFRACTION VECTOR SHIFT OBSERVED IN HETEROGENEOUS LANGMUIR-BLODGETT MULTILAYER FILMS 査読

Y NOGAMI, K OGASAWARA, S TAKEUCHI, T ISHIGURO, K OHSUMI, Y SHIMIZUGAWA

ELECTRICAL, OPTICAL, AND MAGNETIC PROPERTIES OF ORGANIC SOLID STATE MATERIALS 247 835 - 840 1992年

SUPERCONDUCTING TRANSITION IN KAPPA-BEDT-TTF SALTS UNDER MAGNETIC-FIELD 査読

H ITO, Y NOGAMI, M WATANABE, T ISHIGURO, T KOMATSU, G SAITO, N HOSOITO

ELECTRICAL, OPTICAL, AND MAGNETIC PROPERTIES OF ORGANIC SOLID STATE MATERIALS 247 495 - 500 1992年

SUPERCONDUCTING TRANSITION IN KAPPA-(BEDT-TTF)2CU[N(CN)2]BR UNDER MAGNETIC-FIELD 査読

H ITO, M WATANABE, Y NOGAMI, T ISHIGURO, T KOMATSU, G SAITO, N HOSOITO

PHYSICA C 185 2659 - 2660 1991年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Interlayer and intralayer coherence lengths of kappa-(BEDT-TTF)2Cu[N(CN)2]Br are derived as xi-b(0) = 6 +/- 2 angstrom, xi-ac(0) = 24 +/- 5 angstrom, respectively, by magnetic measurement. The renormalized theory of the order parameter fluctuation near the superconducting transition region was employed for the analysis. The broad resistive transitions under magnetic field are discussed on the same footing.

DOI： 10.1016/0921-4534(91)91451-9

Magnetic determination of ginzburg-landau coherence length for organic superconductor κ-(BEDT-TTF)2 X (X = Cu(NCS)2, CuLN(CN)2]Br): Effect of isotope substitution 査読

Hiroshi Ito, Masashi Watanabe, Yoshio Nogami, Takehiko Ishiguro, Tokutaro Komatsu, Gunzi Saito, Nobuyoshi Hosoito

Journal of the Physical Society of Japan 60 ( 10 ) 3230 - 3233 1991年10月

記述言語：英語出版者・発行元：一般社団法人日本物理学会

The Ginzburg-Landau coherence lengths are determined from the temperature dependence of the magnetization by fitting measured results with the renormalization theory of the fluctuation developed for layered superconductors. The derived interlayer coherence lengths are 6 ± 2 Å and 3.2 ± 0.5 Å for κ-(BEDTTTF)2 Cu[N(CN)2]Br and ,κ-(BEDT-TTF)2Cu(NCS)2, respectively, which are remarkably shorter than the interlayer spacing. It is also found that these coherence lengths are virtually unaffected by isotope substitution in BEDT-TTF molecules.

DOI： 10.1143/JPSJ.60.3230

OVERVIEW OF ORGANIC SUPERCONDUCTOR KAPPA-(BEDT-TTF)2[CU(NCS)2] AND ITS RELATED MATERIALS 査読

G SAITO, H YAMOCHI, T NAKAMURA, T KOMATSU, T ISHIGURO, Y NOGAMI, Y ITO, H MORI, K OSHIMA, M NAKASHIMA, S UCHIDA, H TAKAGI, S KAGOSHIMA, T OSADA

SYNTHETIC METALS 42 ( 1-2 ) 1993 - 1998 1991年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

Crystal structures and physical properties of organic superconductors kappa-(BEDT-TTF)2Cu(NCS)2, kappa-(BEDT-TTF)2Cu[N(CN)2]Br and alpha-(BEDT-TTF)2[NH4Hg(SCN)4] are discussed. The Cu(NCS)2 salt shows an inverse isotope effect. The Cu[N(CN)2]Br salt shows Tc of 11.7-11.8K. Conductivities, Hc2 values and lattice parameters of these kappa-type salts are compared.

DOI： 10.1016/0379-6779(91)91998-P

TENSILE STRAIN EFFECTS ON KAPPA-(BEDT-TTF)2CU(NCS)2 査読

T ISHIGURO, H ITO, Y NOGAMI, Y UEBA, H KUSUHARA

SYNTHETIC METALS 42 ( 1-2 ) 1911 - 1914 1991年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

Through the comparison of uniaxial and biaxial tensile strain experiments with the calculated, the dominance of the interlayer interaction for the superconductivity and the resistance maximum in kappa-(BEDT-TTF)2Cu(NCS)2 is presented.

DOI： 10.1016/0379-6779(91)91979-K

ELECTRONIC STATE DENSITY OF HIGHLY CONDUCTING POLYACETYLENE 査読

Y NOGAMI, H KANEKO, T ISHIGURO, N HOSOITO, J TSUKAMOTO, A TAKAHASHI

SYNTHETIC METALS 41 ( 1-2 ) 117 - 120 1991年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

The density of states of heavily I-doped highly conducting polyacetylene (HCPA) is evaluated through the magnetic susceptibility and the thermoelectric power measurements. According to the magnetic susceptibility, the density grows from approximately 4 % (in I-3-unit) doping level, in agreement with previous reports, but the attained value at approximately 9 % (saturating doping level) becomes larger than that for conventional polyacetylene.

DOI： 10.1016/0379-6779(91)91015-3

LOW-TEMPERATURE TRANSPORT-PROPERTIES OF HIGHLY CONDUCTING POLYACETYLENE 査読

Y NOGAMI, H KANEKO, H ITO, T ARAI, A MATSUBARA, T ISHIGURO, N TOYOTA, T SASAKI, J TSUKAMOTO, A TAKAHASHI

SYNTHETIC METALS 41 ( 1-2 ) 95 - 98 1991年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA LAUSANNE

The temperature dependence of the electrical conductivity of the newly developed highly conducting polyacetylene, down to 60 mK, and its high field magnetoconductance up to 15 T are presented. The observed positive magnetoconductance for the most conducting sample exceeds by far the value based on the weak localization theory. The low temperature transport properties vary drastically with small change in the room-temperature conductivity, suggesting that the metallic conduction is realized in the scheme close to metal-nonmetal boundary.

DOI： 10.1016/0379-6779(91)91008-X

LOW-TEMPERATURE ELECTRICAL-CONDUCTIVITY OF HIGHLY CONDUCTING POLYACETYLENE IN A MAGNETIC-FIELD 査読

NOGAMI Y, KANEKO H, ITO H, ISHIGURO T, SASAKI T, TOYOTA N, TAKAHASHI A, TSUKAMOTO J

Physical Review B 43 ( 14 ) 11829 - 11839 1991年

ON THE METALLIC STATES IN HIGHLY CONDUCTING IODINE-DOPED POLYACETYLENE 査読

Y NOGAMI, H KANEKO, T ISHIGURO, A TAKAHASHI, J TSUKAMOTO, N HOSOITO

SOLID STATE COMMUNICATIONS 76 ( 5 ) 583 - 586 1990年11月

HIGH-RESOLUTION X-RAY-SCATTERING STUDY OF THE ANION ORDERING PHASE-TRANSITION OF (TMTSF)2CLO4 査読

JP POUGET, S KAGOSHIMA, T TAMEGAI, Y NOGAMI, K KUBO, T NAKAJIMA, K BECHGAARD

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 59 ( 6 ) 2036 - 2053 1990年6月

THE SUPERSTRUCTURE OF THE ORGANIC SUPERCONDUCTOR BETA-(BEDT-TTF)2I3 UNDER PRESSURE 査読

Y NOGAMI, S KAGOSHIMA, H ANZAI, M TOKUMOTO, N MORI, N KINOSHITA, G SAITO

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 59 ( 1 ) 259 - 265 1990年1月

UNIAXIAL-STRESS EFFECTS ON ORGANIC SUPERCONDUCTOR KAPPA-(BEDT-TTF)2CU(NCS)2 査読

T ISHIGURO, H ITO, Y NOGAMI, Y UEBA, H KUSUHARA

ORGANIC SUPERCONDUCTIVITY 123 - 131 1990年

STRUCTURAL STUDIES OF (TMTSF)2SBCL2F4, ALPHA-(BEDT-TTF)2L3 AND SOME ORGANIC SUPERCONDUCTORS FOUND RECENTLY 査読

S KAGOSHIMA, Y NOGAMI

JOURNAL OF MOLECULAR ELECTRONICS 5 ( 4 ) 201 - 206 1989年10月

2K-SUPERCONDUCTING STATE WITH LESS DISORDER IN THE ORGANIC SUPERCONDUCTOR BETA-(BEDT-TTF)2I3 査読

S KAGOSHIMA, M HASUMI, Y NOGAMI, N KINOSHITA, H ANZAI, M TOKUMOTO, G SAITO

SOLID STATE COMMUNICATIONS 71 ( 10 ) 843 - 846 1989年9月

A CHANGE OF THE SUPERSTRUCTURE AND AN ASSOCIATED RISE OF THE SUPERCONDUCTING CRITICAL-TEMPERATURE IN THE ORGANIC SUPERCONDUCTOR BETA-(BEDT-FFT)2I3 査読

S KAGOSHIMA, Y NOGAMI, M HASUMI, H ANZAI, M TOKUMOTO, G SAITO, N MORI

SOLID STATE COMMUNICATIONS 69 ( 12 ) 1177 - 1180 1989年3月

PHYSICAL-PROPERTIES OF BETA-(BEDT-TTF)2ICL2 査読

A UGAWA, Y OKAWA, K YAKUSHI, H KURODA, A KAWAMOTO, J TANAKA, M TANAKA, Y NOGAMI, S KAGOSHIMA, K MURATA, T ISHIGURO

SYNTHETIC METALS 27 ( 1-2 ) A407 - A412 1988年12月

STRUCTURAL-PROPERTIES OF ORGANIC SUPERCONDUCTORS (DMET)2X AND (BEDT-TTF)2CU(NCS)2 査読

S KAGOSHIMA, Y NOGAMI

SYNTHETIC METALS 27 ( 1-2 ) A299 - A304 1988年12月

X-Ray Studies of Structural Changes in Superconducting and Non-Superconducting BEDT-TTF Salts : III. Organics :

Seiichi Kagoshima, Yoshio Nogami

JJAP series 1 181 - 184 1988年

Possible Appearance of Spin-Density Waves in the Insulating Phase of the Organic Conductors, (DMET)2Au(CN)2 and (DMET)2AuI2

Nogami Yoshio, Tanaka Masanori, Kagoshima Seiichi, Kikuchi Koichi, Saito Kazuya, Ikemoto Isao, Kobayashi Keiji

J Phys Soc Jpn 56 ( 11 ) 3783 - 3785 1987年11月

Magnetic and Structural Properties of the High-$T_{\text{c } }$ Superconductor Ho–Ba–Cu Oxide

Kagoshima Seiichi, Koga Kei-ichi, Yasuoka Hiroshi, Nogami Yoshio, Kubo Koichi, Hikami Shinobu

Jpn J Appl Phys 26 ( 4 ) L355 - L357 1987年4月

記述言語：英語出版者・発行元：社団法人応用物理学会

The title material is found to have the crystal structure same as another superconductor, Y–Ba–Cu oxide. The lattice has the face-centered tetragonal symmetry and the unit cell, whose parameters are $a{=}b{=}7.81\pm 0.02$ Å and $c{=}7.665\pm 0.02$ Å, contains eight units of the perovskite structure. The magnetic susceptibility obeys essentially the Curie-Weiss formula when sufficient fields are applied. For the fields less than 200 Oe the Meissner effect is observed up to about 70 K above which a finite resistance is found. The diamagnetic susceptibility at 4.4 K reaches about 50% of a perfect diamagnetism.

DOI： 10.1143/JJAP.26.L355

Characterization of the High-$T_{\text{c } }$ Superconductor Y–Ba–Cu Oxide —Critical Current and Crystal Structure—

Kagoshima Seiichi, Hikami Shinobu, Nogami Yoshio, Hirai Takashi, Kubo Koichi

Jpn J Appl Phys 26 ( 4 ) L318 - L319 1987年4月

記述言語：英語出版者・発行元：社団法人応用物理学会

Critical currents are measured in the title material. At 9.5 K, where an apparent resistance is zero, the critical-current density $J_{\text{c } }$ is found to be about 1.7 A/cm2 in a sintered sample. For currents smaller than $J_{\text{c } }$ the sample resistivity is less than 2.3 $\mu\Omega\cdot$cm. By X-ray diffraction the crystal structure is found to be essentially of a perovskite type. Its unit cell composed of eight units of the perovskite structure has a face-centered tetragonal symmetry with the lattice parameters $a{=}b{=}7.83\pm 0.02$ Å and $c{=}7.72\pm 0.03$ Å.

DOI： 10.1143/JJAP.26.L318

Characterization of the High-Tc Superconductors Rare-Earth–Ba–Cu Oxides–Resistivity, Susceptibility and Structure– 査読

Seiichi Kagoshima, Toshihiro Takahashi, Kazushi Kanoda, Masahiko Hasumi, Takashi Hirai, Yoshio Nogami, Kei-Ichi Koga, Hiroshi Yasuoka, Hidetoshi Minami, Taizo Masumi, Shinobu Hikami

Japanese Journal of Applied Physics 26 ( 3-2 ) 1033 - 1034 1987年

記述言語：英語掲載種別：研究論文（学術雑誌）

Polycrystalline samples of the high-transition temperature superconductors Y-Ba-Cu, Ho-Ba-Cu and Gd-Ba-Cu oxides are characterized by resistivity, susceptibility, and x-ray measurements. Measured magnetic moments are ascribed mostly to magnetic rare-earth ions, and partly to Cu2+ ions and some other crystal phases. It is found that an oxygen pressure and a sample-preparation temperature dominate the amount of the Cu2+ ions and of other phases, respectively. © 1987 The Japan Society of Applied Physics.

DOI： 10.7567/JJAPS.26S3.1033

X-RAY EVIDENCE FOR STRUCTURAL-CHANGES IN THE ORGANIC CONDUCTORS, ALPHA-(BEDT-TTF)2I3, ALPHA-(BEDT-TTF)2IBR2 AND BETA-(BEDT-TTF)2I3 査読

Y NOGAMI, S KAGOSHIMA, T SUGANO, G SAITO

SYNTHETIC METALS 16 ( 3 ) 367 - 377 1986年12月

有機超伝導体ビス（エチレンジチオ）‐テトラチアフルバレン塩の構造変態

野上由夫, 鹿児島誠一, 斉藤軍治

日本化学会誌 1986 ( 3 ) 490 - 496 1986年3月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人日本化学会

有機超伝導体BEDT-TTF塩について構造と伝導の関連について調べた。圧力印加を経験したβ-(BEDT-TTF)<SUB>2</SUB>I<SUB>3</SUB>塩は, 超伝導転移温度T<SUB>c</SUB>が1.5→8Kまで上昇することが知られている。また常圧で不整合超格子q=(0.08, 0.27, 0.205)が200K以下で出現することも発見されている。圧力印加によって超格子出現が抑えられ, その結果T<SUB>c</SUB>が上昇するという仮説をたて, 圧力印加を経験した試料についてX線で衛星反射強度を観灘することにより, 超格子出現温度を測定した。その結果, 圧力印加を経験しても超格子の挙動は変化しないという否定的データを得た。(BEDT-TTF)<SUB>2</SUB>IBr<SUB>2</SUB>塩は半導体的な電気伝導をもち, 活性化エネルギーが低温で増加する。この半導体相(BEDT-TTF)<SUB>2</SUB>IBr<SUB>2</SUB>塩では低温になるにつれて分子のご量体化が起こることを発見した。二量体化の進行が活性化エネルギーの増加を引き起こすと思われる。この塩では130K付近に, 別の構造変化があることも推測される。

X-RAY STUDY OF FIELD-INDUCED DEFORMATION OF SLIDING CDW IN K0.30MOO3 査読

T TAMEGAI, K TSUTSUMI, S KAGOSHIMA, Y KANAI, H TOMOZAWA, M TANI, Y NOGAMI, M SATO

SOLID STATE COMMUNICATIONS 56 ( 1 ) 13 - 16 1985年

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