研究者詳細 - 池田　直

論文 - 池田　直

分割表示 209 件中 141 - 160 件目／全件表示 >>

X-ray Diffuse Scattering Study of Modulated Structure in θ-(BEDT-TTF)₂CsM'(SCN)₄ Under Electric Field

Y. Nogami, Masashi Watanabe, Naoshi Ikeda, T. Ito, K. Yamamoto, Yukio Noda, I. Terasaki, H. Mori, T. Mori

SPring-8 User Experiment Reports 2005A 2006年

X-ray and neutron transparent pulse magnets

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

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Conduction characteristics of charge ordering type ferroelectrics,YFe2O

K. Imamura, Y. Horibe, T. Yoshimura, N. Fujimura, S. Mori, N. Ikeda

Materials Research Society Symposium Proceedings 966 210 - 216 2006年

Development of X-ray Analysis Method for Topological Crystals

K. Yamamoto, T. Ito, N. Ikeda, S. Horita, N. Irie, Y, Nogami T. Tsuneta, S. Tanda

Topology in Ordered Phase (World Scientific) 86-94 2006年

Structure Analysis of Topological Crystal using Synchrotron Radiation

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

Topology in Ordered Phase (World Scientific) 52-57 2006年

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

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

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Structure, magnetism and transport of the perovskite manganites Ln(0.5)Ca(0.5)MnO(3) (Ln = Ho, Er, Tm, Yb and Lu)

K Yoshii, H Abe, N Ikeda

JOURNAL OF SOLID STATE CHEMISTRY 178 ( 12 ) 3615 - 3623 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：ACADEMIC PRESS INC ELSEVIER SCIENCE

It was found that the manganese perovskite oxides Ln(0.5)Ca(0.5)MnO(3) (Ln = Ho, Er, Tm, Yb and Lu) have an orthorhombic structure (space group Pnma). The Mn-O-Mn angles were calculated to be similar to 148-150 degrees, revealing an existence of a large crystallographic distortion in these oxides. Electrical resistivity measurements indicated both an insulating nature and a small magnetoresistance effect, both of which are owing to narrow bandwidths of the Mn-3d electrons arising from the crystallographic distortion. DC magnetization measurements showed the three characteristic temperatures, which could be assigned to charge-order, antiferromagnetism or Mn moments, and possible glassy states. All of these temperatures were decreased for the heavier Ln ions, which is explained in connection with both a difference of ionic radii of Ln(3+) and Ca2+, and a lowering of electron transfer. The charge-ordering transition was not clearly observed only for Lu0.5Ca0.5MnO3 containing the smallest lanthanide ion, plausibly due to a large randomness of magnetic interactions arising from the ionic radii difference of Lu3+ and Ca2+. In addition, preliminary measurements of AC dielectric response suggested that these manganites belong to a so-called multiferroic system. (C) 2005 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jssc.2005.08.033

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Nano-sized domains related to dielectric anomaly in YFe2O4-δ

Y. Horibe, K. Kishimoto, S. Mori, N. Ikeda

J. Electron Microsc. 54 I87 - I90 2005年9月

Ferro-type orbital state in the mott transition system Ca2-xSrxRuO4 studied by the resonant X-ray scattering interference technique

M Kubota, Y Murakami, M Mizumaki, H Ohsumi, N Ikeda, S Nakatsuji, H Fukazawa, Y Maeno

PHYSICAL REVIEW LETTERS 95 ( 2 ) 2005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

We have succeeded in detecting ferro-type orbital states in Ca2-xSrxRuO4, which is the first outcome in a 4d Mott transition system by the resonant x-ray scattering interference technique. For x=0 (Mott insulator), the resonant signal for d(xy) orbital ordering is observed even at room temperature, in which the Jahn-Teller distortion is negligible. The signal disappears near the metal-insulator transition. On the other hand, in a metallic phase for x=0.5, orbital polarization with d(yz/zx) character dominates. With lowering temperature, the magnitude of the resonant signal slightly decreases owing to the additional influence of the gamma band with d(xy) character.

DOI： 10.1103/PhysRevLett.95.026401

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Structural properties and phase transition of hole-orbital-ordered (C2H5NH3)(2)CuCl4 studied by resonant and non-resonant x-ray scatterings under high pressure

K Ohwada, K Ishii, T Inami, Y Murakami, T Shobu, H Ohsumi, N Ikeda, Y Ohishi

PHYSICAL REVIEW B 72 ( 1 ) 2005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

The effects of hydrostatic pressure on a structure and the corresponding resonant x-ray scattering (RXS) spectrum have been investigated for the hole-orbital-ordered compound (C2H5NH3)(2)CuCl4. We have found a structural phase transition at P-c similar to 4 GPa, as suggested by the Raman scattering measurement, by observing a peak splitting resulting from an orthorhombic-to-monoclinic symmetry breaking. The reduction of the Jahn-Teller distortion (JTD) toward P-c is also ascertained by structural analyses. The gradual change in the color of the crystal is also observed in connection with the structural change near P-c. The red-colored transparency of the crystal indicates that the system is still insulative above P-c. The observed RXS and fluorescence spectrum at ambient pressure were precisely analyzed. We experimentally confirmed that the RXS intensity comes from the polarization of the density of states of p(x) and p(y) symmetries, which is mainly dominated not by the on-site 3d-4p Coulomb interaction but by the JTD of the CuCl6 octahedron. charged Cl ions neighboring the Cu site. It is also expected that the RXS intensity is proportional to JTD; however, our RXS study under a high pressure shows no striking change as JTD is suppressed by the application of pressure. On the other hand, the RXS intensity becomes zero above P-c. The results indicate that the local environment of the Cu2+ ion markedly changes. Two possible structures of EA(2)CuCl(4) above P-c are proposed.

DOI： 10.1103/PhysRevB.72.014123

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Determination of a merocyanine J-aggregate structure and the significant contribution of the electric dipole interaction to the exciton band wavelength

N Kato, K Yuasa, T Araki, Hirosawa, I, M Sato, N Ikeda, K Iimura, Y Uesu

PHYSICAL REVIEW LETTERS 94 ( 13 ) 2005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：AMER PHYSICAL SOC

The molecular alignment of a merocyanine (MC) J-aggregate monolayer at the air-water interface was determined by a grazing incidence x-ray diffraction method. The obtained molecular arrangement apparently shows that the conventional formula, which accounts only for the transition dipole interaction, is not sufficient to figure out the exciton band wavelength, suggesting the importance of the electric dipole (ED) interaction. We derived a simple formula for the ED interaction energy under an extended dipole approximation and clarified the ED contribution in the MC J aggregate.

DOI： 10.1103/PhysRevLett.94.136404

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Structural phase transitions and dielectric anomaly in YFe2O4-delta

Y Horibe, K Kishimoto, S Mori, N Ikeda

JOURNAL OF THE KOREAN PHYSICAL SOCIETY 46 ( 1 ) 192 - 194 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：KOREAN PHYSICAL SOC

We examined structural changes related to charge ordering (CO) in the temperature window between 100 K and room temperature (BT) in YFe2O4-delta by transmission electron microscopy. Characteristic diffuse scattering elongated along the [001] direction through the (1/3 1/3 0)-type reciprocal positions was found at RT, which is related to the microdomains due to the CO with a size of 10 - 20 run. In addition, it was also found that the superlattice structures characterized by the (1/3 - eta1/3 + eta0)-type modulation vector, which should be due to the vacancy ordering, coexist with the microdomains due to the CO. On the other hand, in stoichimetric YFe2O4, We found temperature variations of the superlattice structures on warming from 100 K, which should be strongly related to the dielectric anomalies in YFe2O4.

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Grazing incidence X-ray diffraction of merocyanine J-aggregate monolayers at the air-water interface

N. Kato, K. Yuasa, T. Araki, Y. Uesu, I. Hirosawa, M. Sato, N. Ikeda, K. Iimura

Trans. Mat. Res. Soc. Jpn. 2005年

Charge ordering and dielectric dispersion in mixed valence oxides RFe2O4

N Ikeda, S Mori, K Kohn

FERROELECTRICS 314 41 - 56 2005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

In a series of oxides RFe2O4 (R = rare earth between Dy and Lu, or Y), equal numbers of Fe2+ and Fe3+ are located on a layer composed of two triangular nets stacked together. These oxides have several phase transitions where the arrangement of Fe2+ and Fe3+ ions transforms from one type to another. Unique dielectric properties of these oxides have been explained in connection with the charge ordering.
Recent developments on the structure of the ordered phases are reviewed with comments on their correlation with the observed dielectric dispersion.

DOI： 10.1080/00150190590926085

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Structural phase transition of J-aggregate crystallites on the binary counter-ion subphase

N Kato, T Araki, Y Uesu, M Sato, Hirosawa, I, N Ikeda, K Iimurac

FERROELECTRICS 314 135 - 141 2005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

The recently found chromic phase transition of merocyanine J-aggregates monolayer on the aqueous subphase containing Cd2+ and Mg2+ was investigated by the grazing incidence X-ray diffraction method. The evidence of the structural difference between the phases of J-band at 620 nm and 590 nm was obtained by the investigations on the monolayers prepared at the different molar ratios of Cd2+ and Mg2+. The change in a Bragg's peak was observed at the ratio of the ions, where the J-band wavelength also exhibited the discrete shift. The relationship between the obtained results and the phase diagram determined by the shift of the J-band wavelength was also discussed from the viewpoint of the formation mechanism of J-aggregate crystallites.

DOI： 10.1080/00150190590926319

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Diffuse Scattering in θ-(BEDT-TTF)₂CsZn(SCN)₄ under Electric Field at Low temperature

N. Ikeda, M. Watanabe, T. Ito, Y. Nogami, S. Komiyama, Y. Noda, I. Terasaki, H. Mori, T. Mori

SPring-8 User Experiment Report 14 301 - 301 2005年

Decrease in X-ray diffuse scattering intensity reflecting two-fold structural modulation in θ-(BEDT-TTF)₂CsZn(SCN)₄ under Electric Field

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

SPring-8 User Experiment Report 15 18 - 18 2005年

Spin-Peierls Transition in Halogen-Bridged Mixed-Valence MMX Chain Compounds

Koshiro Toriumi, Minoru Mitsumi, Yuji Yoshida, Akihisa Kohyama, Naoshi Ikeda, Nobuhiro Yasuda, Yoshiki Ozawa

ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES 61 C327 - C327 2005年

Structural properties and phase transition of hole-orbital-ordered (C2H5NH3)2CuCl4 studied by resonant and non-resonant x-ray scatterings under high pressure 査読

Kenji Ohwada, Kenji Ishii, Toshiya Inami, Youichi Murakami, Takahisa Shobu, Hiroyuki Ohsumi, Naoshi Ikeda, Yasuo Ohishi

Physical Review B - Condensed Matter and Materials Physics 72 ( 1 ) 2005年

記述言語：英語掲載種別：研究論文（学術雑誌）

The effects of hydrostatic pressure on a structure and the corresponding resonant x-ray scattering (RXS) spectrum have been investigated for the hole-orbital-ordered compound (C2H5NH3)2CuCl4. We have found a structural phase transition at Pc∼4GPa, as suggested by the Raman scattering measurement, by observing a peak splitting resulting from an orthorhombic-to-monoclinic symmetry breaking. The reduction of the Jahn-Teller distortion (JTD) toward Pc is also ascertained by structural analyses. The gradual change in the color of the crystal is also observed in connection with the structural change near Pc. The red-colored transparency of the crystal indicates that the system is still insulative above Pc. The observed RXS and fluorescence spectrum at ambient pressure were precisely analyzed. We experimentally confirmed that the RXS intensity comes from the polarization of the density of states of px and py symmetries, which is mainly dominated not by the on-site 3d-4p Coulomb interaction but by the JTD of the CuCl6 octahedron. charged Cl ions neighboring the Cu site. It is also expected that the RXS intensity is proportional to JTD
however, our RXS study under a high pressure shows no striking change as JTD is suppressed by the application of pressure. On the other hand, the RXS intensity becomes zero above Pc. The results indicate that the local environment of the Cu2+ ion markedly changes. Two possible structures of EA2CuCl4 above Pc are proposed. © 2005 The American Physical Society.

DOI： 10.1103/PhysRevB.72.014123

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Dielectric anomaly and structural phase transitions in YFe 2O4-δ

Y. Horibe, K. Kishimoto, S. Mori, N. Ikeda

Integrated Ferroelectrics 67 151 - 157 2004年12月

We examined structural changes related to the charge ordering (CO) in the temperature window between 100K and room temperature (RT) in YFe2O4-δby transmission electron microscopy. Characteristic diffuse scattering elongated along the [001] direction through the (1/3 1/3 0)-type reciprocal positions was found at RT, which is related to nano-sized domains due to the CO. In addition, we found the presence of the superlattice structures characterized by the (1/4 1/4 0)-type modulation vector at 150K and by the (0 1/2 0)-type modulation vector at 200 K. The changes in the superlattice structures as a function of the temperature should be strongly related to the dielectric anomalies in YFe2O4-δ.

DOI： 10.1080/10584580490898876

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