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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

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