研究者詳細 - 池田　直

論文 - 池田　直

分割表示 209 件中 81 - 100 件目／全件表示 >>

Magnetic and dielectric study of R0.5Sr0.5MnO3 (R = Gd, Tb and Dy)

Kenji Yoshii, Yusuke Hiramitsu, Yuka Okajima, Yasuhiro Yoneda, Yasuo Nishihata, Jun'ichiro Mizuki, Akio Nakamura, Yutaka Shimojo, Yoshinobu Ishii, Yukio Morii, Naoshi Ikeda

MATERIALS RESEARCH BULLETIN 45 ( 11 ) 1574 - 1580 2010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：PERGAMON-ELSEVIER SCIENCE LTD

Magnetic and dielectric properties of perovskite manganites R0.5Sr0.5MnO3(R = Gd, Tb and Dy) have been investigated. DC and AC magnetic measurements showed short-range glassy magnetic ordering at T-g similar to 40 K. Such ordering was observed by neutron diffraction and is ascribable to the size mismatch of R3+ and Sr3+ settled randomly at the same crystallographic site. Dielectric constants for each material were similar to 1000-10,000 between similar to 50 and similar to 300 K and showed broad maximums above T-g. Dielectric dispersion showed poor coherency of the motion of polar regions, plausibly because of the size-mismatch effect; both the magnetic and dielectric properties of this system are governed by the randomness at the R/Sr site. The tan delta and EXAFS data suggest that the dielectric response is rooted in a transfer of the Mn-3d electrons. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.materresbull.2010.07.024

Quantitative analysis of O-2 gas sensing characteristics of picene thin film field-effect transistors

Xuesong Lee, Yasuyuki Sugawara, Akio Ito, Shuhei Oikawa, Naoko Kawasaki, Yumiko Kaji, Ryoji Mitsuhashi, Hideki Okamoto, Akihiko Fujiwara, Kenji Omote, Takashi Kambe, Naoshi Ikeda, Yoshihiro Kubozono

ORGANIC ELECTRONICS 11 ( 8 ) 1394 - 1398 2010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 BV

O-2 gas sensing behaviors are studied in picene thin film field-effect transistors (FETs) with hydrophobic polymer (Cytop(TM) or polystyrene) coated SiO2 gate dielectrics. Picene thin film FETs show a rapid reduction of hysteresis in transfer curves recorded in forward and reverse measurement modes, compared to a picene FET with hexamethydisilazane-coated SiO2. The picene FETs show very sensitive O-2 gas sensing effects down to similar to 10 ppm. A quantitative analysis is presented of the gate voltage (V-G) dependent mobility induced by O-2 exposure, i.e., the suppression of drain current at high V-G. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.orgel.2010.06.003

Relaxation of geometrical frustration in NbSe3 topological crystals

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

PHYSICAL REVIEW B 82 ( 1 ) 014105 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

Charge Order Competition Leading to Nonlinearity in Organic Thyristor Family

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 ) 44606 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

Growth and characterization of bismuth magnesium titanate Bi(Mg 1/2Ti1/2)O3

Yasuhiro Yoneda, Hiroyuki Saitoh, Kenji Yoshii, Takashi Nishida, Hironori Hayakawa, Naoshi Ikeda

Key Engineering Materials 421-422 3 - 8 2010年2月

A new oxide, Bi(Mg1/2Ti1/2)O3 was prepared using a high-pressure high-temperature technique at 8 GPa and 1000°C. As-sintered Bi(Mg1/2Ti1/2)O3 has the BiFeO 3-type perovskite structure with the rhombohedral R3c. After ground, crystal structure changed to tetragonal P4mm. Structure parameters of tetragonal Bi(Mg1/2Ti1/2)O3 were refined from laboratory X-ray powder diffraction data (a = 4.033(10) Å, and c = 3.938(10) Å). Bi(Mg1/2Ti1/2)O3 does not decompress at ambient pressure, but the structure changed from rhombohedral to tetragonal on heating above 800° C. This phase transition was nonreversible. Bi(Mg 1/2Ti1/2)O3 is expected to be one of the end members of lead-free ferroelectric materials. © (2010) Trans Tech Publications.

DOI： 10.4028/www.scientific.net/KEM.421-422.30

Doping effect on charge ordered structure in RFe<inf>2</inf>O<inf>4</inf> (R=Lu and Yb)

Y. Matsuo, S. Mori, A. Hirata, K. Yoshii, N. Ikeda

Journal of Physics: Conference Series 200 2010年1月

Doping effects on the charge ordered (CO) structure in RFe 2O4 (R=Lu, Yb) were investigated by an energy-filtered transmission electron microscope (EF-TEM), in combination with conventional magnetic measurement. The repalcement of Cu2+ and Co2+ for Fe2+ in RFe2O4 (R=Lu, Yb) destroyed drastically the CO structure. In LuFeCuO4, the CO structure with q=1/3 1/3 1/2 disappear and short-ranged domains consisting of cationic ordering of Fe3+ and Cu2+ ions are formed, which gives rise to characteristic zigzag-shaped diffuse streaks with diffuse spots at the h/3-δ h/3-δ 0-type positions (h: integer, δ=0.06) in reciprocal space. In addition, the magnetic measurement revealed that LuFeCuO4 exhibits a magnetic transition around 50K, which is much lower than the Neel temperature of 250K in LuFe2O4. In YbFeCoO4, clusters consisting of Fe3+ and Co2+ in the triangular lattice are formed and give rise to honeycomb-shaped diffuse streaks. © 2010 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/200/1/012128

Multi-ferroicity of thin-film-stabilized hexagonal YbFeO<inf>3</inf>

Y. Uesu, H. Iida, T. Koizumi, K. Kohn, S. Mori, N. Ikeda, R. Haumont, J. M. Kiat

Proceedings of the 2010 IEEE International Symposium on the Applications of Ferroelectrics, ISAF 2010, Co-located with the 10th European Conference on the Applications of Polar Dielectrics, ECAPD 2010 2010年1月

The modulated structure and ferromagnetic insulating state in a nine-layer BaRuO3

Chao-Hung Du, Chang-Hung Yao, Dah-Chin Ling, Mau-Tsu Tang, Fon-Chi Hsu, Hsiang-Lin Liu, P. D. Hatton, Naoshi Ikeda

JOURNAL OF PHYSICS-CONDENSED MATTER 22 ( 3 ) 3036003 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：IOP PUBLISHING LTD

We report the observation of a modulated structure and a ferromagnetic insulating state in a high quality single crystal of a nine-layer BaRuO3. Using x-ray scattering, the modulated satellites were observed to double the unit cell along the c-axis at low temperature. The ferromagnetic insulating state is confirmed by magnetic and resistivity measurements. Analyzing the peak profiles from the modulation and host structure respectively, showed a lattice distortion at T similar to 55 K. These findings elucidate the intimate relationship between ferromagnetism and lattice distortion in a nine-layer BaRuO3.

DOI： 10.1088/0953-8984/22/3/036003

Magneto-electric effect in charge-ordered LuFe2O4

Takashi Kambe, Takuma Komatsu, Takamasa Michiuchi, Hiroki Hayakawa, Daisuke Ohishi, Noriaki Hanasaki, Kenji Yoshii, Naoshi Ikeda

INTERNATIONAL CONFERENCE ON MAGNETISM (ICM 2009) 200 012077 2010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 magneto-electric (ME) effect was observed in a charge-ordered ferroelectric LuFe2O4. The dielectric response in a three-dimensional charge-ordered phase is strongly influenced by magnetic field, especially around the fern-magnetic ordering temperature. We also show the relation between the oxygen stoichiometry and the ME signal character above the magnetic transition temperature.

DOI： 10.1088/1742-6596/200/1/012077

High Pressure and Temperature Synthesis of Bi-based Perovskite (Bi0.5Na0.5-xLix)TiO3

Masanori Fukunaga, Yasuhiro Yoneda, Ryota Fukuyama, Hiroyuki Saitoh, Naoshi Ikeda, Yoshinori Katayama

Transactions of the Materials Research Society of Japan 35 ( 1 ) 111 - 114 2010年

Structural characterization and dielectric properties of hexagonal Lu(Fe, Ti)O<inf>3</inf>

Yoji Matsuo, Takuya Hoshiyama, Shigeo Mori, Kenji Yoshii, Yuichi Michiue, Takashi Kambe, Naoshi Ikeda, Francisco Brown, Noboru Kimizuka

Japanese Journal of Applied Physics 48 ( 9 ) 09KB04 - 09KB04-3 2009年12月

記述言語：英語出版者・発行元：Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physics

We investigated the average crystal structure and microstructures of LuFe0.56Ti0.44O3 by transmission electron microscopy (TEM) in combination with dielectric measurements. In this work, high-quality polycrystalline samples of LuFeM0.56Ti 0.44O3 were successfully synthesized in air by the conventional solid-state reaction. The average crystal structure at room temperature is characterized by a hexagonal structure (space group: P6 3cm). Dielectric measurements revealed that LuFe 0.56Ti0.44O3 shows broad dielectric peaks at approximately 450 and 580K, one of which is considered to originate from the formation of polar domains at the nanometer scale. © 2009 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.48.09KB04

Oxygen-deficient effect on charge ordering in spin- and charge-frustrated ferrite YFe2O4−δ

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

Phys. Rev. B 80 ( 9 ) 092104-092104 2009年9月

Syntheses, Structures and Solid-State Properties of MMX Mixed-Valence Chains, [Ni-2(II/III)(RCS2)(4)I](infinity) (R = Et, n-Pr and n-Bu): Evidence of a Spin-Peierls Transition

Minoru Mitsumi, Yuji Yoshida, Akihisa Kohyama, Yasutaka Kitagawa, Yoshiki Ozawa, Mototada Kobayashi, Koshiro Toriumi, Makoto Tadokoro, Naoshi Ikeda, Mitsutaka Okumura, Mohamedally Kurmoo

INORGANIC CHEMISTRY 48 ( 14 ) 6680 - 6691 2009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 CHEMICAL SOC

The partial oxidation of [Ni-2(II/II)(RCS2)(4)] (R = Et (1), n-Pr (2), and n-Bu (3)) with iodine affords the MMX chain compounds [Ni-2(II/III)(RCS2)(4)I](infinity) (R = Et (4), n-Pr (5), and n-Bu (6)), respectively. The crystal structures of 4-6 consist of neutral one-dimensional (1-D) chains with a repeating -Ni-Ni-I- unit. The room-temperature (RT) structure of 4 indicates a charge-polarization (CP) state {-Ni(2.5-delta)+-Ni(2.5+delta)+I--Ni(2.5-delta)+ -Ni(2.5+delta)+-I- (delta << 0.5)} close to an averaged valence state judged by the Ni-I distances. In contrast, 5 and 6 exhibit a Vold periodicity of a -Ni-Ni-l- unit due to the disorder of the dithiocarboxylato ligands. Compounds 4-6 show typical semiconducting behavior and exhibit an intense sharp absorption band centered at 5400 cm(-1), which is attributed to a Mott-Hubbard gap due to a relatively large on-site Coulomb repulsion energy U of the nickel atoms. The high-temperature magnetic susceptibilities of 4-6 can be described by a 1-D Heisenberg antiferromagnetic chain model with vertical bar J vertical bar/k(B) ranging from 898(2) to 939(3) K. Compounds 4 and 5 undergo a spin-Peierls (SP) transition at relatively high T-sp = 47 and 36 K, respectively, which are accompanied by superlattice reflections corresponding to a 2-fold -Ni-Ni-l- period below T-sp. By determining the superstructure of 4 at 26 K, we conclude that the valence-ordered state changes from the CP in the RT phase to the altemate charge-polarization (ACP) state of -Ni(2.5-delta)+-Ni(2.5+delta)+-I--Ni(2.5-delta)+-I-Ni(2.5+delta)+-Ni(2.5-delta)+-I- -in the SP phase. Such a spin-Peierls transition could not be observed for 6.

DOI： 10.1021/ic900630a

Magnetic and dielectric properties of YbFe2-xMnxO4 (0 <= x <= 1)

Kenji Yoshii, Naoshi Ikeda, Takamasa Michiuchi, Yusuke Yokota, Yuka Okajima, Yasuhiro Yoneda, Yoji Matsuo, Yoichi Horibe, Shigeo Mori

JOURNAL OF SOLID STATE CHEMISTRY 182 ( 7 ) 1611 - 1618 2009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：ACADEMIC PRESS INC ELSEVIER SCIENCE

We have investigated the magnetic and dielectric properties of YbFe2-xMnxO4 (0 <= x <= 1), which is all Fe-site-substituted system of new multiferroic oxides RFe2O4 (R = Y, Ho-LU). X-ray diffraction measurements show that a solid solution is formed between YbFe2O4 (x = 0) and YbFeMnO4 (X = 1) for (0 <= x <= 1), whereas only compounds with x = 1 (i.e., RM1M2O4: M-1 and M-2 = trivalent and divalent cations, respectively) have been known for the Fe-site substitution in RFe2O4. The valence of the Mn ion is determined to be similar to 2+, consistently with the Suppression of low-temperature magnetization by the Mn substitution. The magnetic transition temperature (T-N) and the dielectric constant (epsilon') decrease monotonically with increasing x. This result plausibly confirms that the magnetic and dielectric properties in oxides isostructural with RFe2O4 are governed by the electron transfer between Fe-site ions, Unlike ordinary ferroelectrics and dielectrics, in which the ionic displacement plays a key role. The possibility for application is briefly discussed as well. (C) 2009 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jssc.2009.04.008

High-performance C-60 and picene thin film field-effect transistors with conducting polymer electrodes in bottom contact structure

Yumiko Kaji, Ryoji Mitsuhashi, Xuesong Lee, Hideki Okamoto, Takashi Kambe, Naoshi Ikeda, Akihiko Fujiwara, Minoru Yamaji, Kenji Omote, Yoshihiro Kubozono

ORGANIC ELECTRONICS 10 ( 3 ) 432 - 436 2009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

C-60 and picene thin film field-effect transistors (FETs) in bottom contact structure have been fabricated with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PED-OT:PSS) electrodes for a realization of mechanical flexible organic FETs. The C-60 thin film FETs showed n-channel enhancement-type characteristics with the field-effect mobility mu value of 0.41 cm(2\) V-1 s(-1), while the picene thin film FET showed p-channel enhancement-type characteristics with the p of 0.61 cm(2) V-1 s(-1). The p values recorded for C-60 and picene thin film FETs are comparable to those for C-60 and picene thin film FETs with Au electrodes. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.orgel.2009.01.006

希土類-鉄酸化物RFe_2O_4の示す新規な強誘電性(R = Y, Ho-Lu)

吉井賢資, 池田直, 松尾祥史, 森茂生

日本結晶学会誌 51 ( 2 ) 162 - 168 2009年4月

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

The rare-earth iron oxides RFe₂O₄ (R = Y, Ho-Lu) have a rhombohedral crystal structure, consisting of an alternating stacking of triangular lattices of R, Fe and O ions. Recently, we have proposed that this system shows a new mechanism of ferroelectricity ; the ferroelectric state originates from a polar charge-ordered structure of Fe²⁺ and Fe³⁺ on a triangular lattice. In this article, a review is given on the details of this ferroelectricity, which were revealed by measurements of synchrotron X-ray diffraction and dielectric properties of one of the RFe₂O₄ oxides, LuFe₂O₄.

DOI： 10.5940/jcrsj.51.162

その他リンク： https://jlc.jst.go.jp/DN/JALC/00331402115?from=CiNii

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

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)

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 ) 24714-024714 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

Local Structure Analysis of Cubic Perovskite CaCu3Ti4O12

Yasuhiro Yoneda, Kenji Yoshii, Hironori Hayakawa, Naoshi Ikeda

Transactions of the Materials Research Society of Japan 34 ( 1 ) 15 - 15 2009年

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

Recently, there has been considerable interest in the dielectric properties of the cubic perovskite CaCu₃Ti₄O₁₂. The material has shown to have relatively high temperature independent dielectric permittivity over a wide temperature range from 100 K to 600 K. Below ～ 100 K the permittivity drops by almost three orders of magnitude, but is not accompanied by a structural phase transition. We studied CaCu₃Ti₄O₁₂ hoping to find signatures of local structural distortions that may explain the observe anomalies in the dielectric properties. Experiments were carried out using synchrotron radiation at several temperatures between room temperature and 10 K. Reconsideration is necessary for interpreting a huge permittivity by the local disorder model.

DOI： 10.14723/tmrsj.34.15

Nanometer-Sized Domain Structures in LuFeMO4 (M = Cu, Co) Revealed by Energy-Filtered Transmission Electron Microscopy

Y. Matuso, A. Hirata, Y. Horibe, K. Yoshii, N. Ikeda, S. Mori

FERROELECTRICS 380 56 - 62 2009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

Diluted effect on the charge ordered (CO) structure in dielectric materials LuFeMO4 (M = Cu, Co) were investigated by an energy-filtered transmission electron microscopy (TEM), in combination with a conventional TEM. It is revealed that partial substitution of Cu2+ and Co2+ for Fe2+ in LuFe2O4 destabilized the CO structure. In LuFeCuO4, there exist characteristic zigzag-shaped diffuse streaks and diffuse spots at the h/3-delta h/3-delta 0-type positions (h: integer, delta = 0.06) in reciprocal space, which originate from static cationic ordering of Fe3+ and Cu2+ ions in the triangular lattice. Moreover, real-space images by the energy-filtered TEM revealed that nanometer-sized domain structures with the 5 similar to 10 nm size are formed. In contrast, honeycomb-shaped diffuse streaks were found in LuFeCoO4, in which no domain structures are observed in real-space images.

DOI： 10.1080/00150190902873204

　前のページ - 次のページ　

1
2
3
4
5
6
7
8
9
10
11