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Journal Articles

SENJU; A New time-of-flight single-crystal neutron diffractometer at J-PARC

Ohara, Takashi; Kiyanagi, Ryoji; Oikawa, Kenichi; Kaneko, Koji; Kawasaki, Takuro; Tamura, Itaru; Nakao, Akiko*; Hanashima, Takayasu*; Munakata, Koji*; Moyoshi, Taketo*; et al.

Journal of Applied Crystallography, 49(1), p.120 - 127, 2016/02

 Times Cited Count:26 Percentile:6.46(Chemistry, Multidisciplinary)

Journal Articles

Instrument design and performance evaluation of a new single crystal neutron diffractometer SENJU at J-PARC

Oikawa, Kenichi; Kawasaki, Takuro; Ohara, Takashi; Kiyanagi, Ryoji; Kaneko, Koji; Tamura, Itaru; Nakamura, Tatsuya; Harada, Masahide; Nakao, Akiko*; Hanashima, Takayasu*; et al.

JPS Conference Proceedings (Internet), 1, p.014013_1 - 014013_5, 2014/03

A new single crystal time-of-flight neutron diffractometer has been installed at BL18 of the Materials and Life Science Experimental Facility of J-PARC. The diffractometer "SENJU" was designed for precise crystal and magnetic structure analyses using a small crystal less than 1.0 mm$$^3$$ under multiple extreme environments such as low-temperature and high-magnetic field. The first neutron beam was delivered to the sample position on March 5, 2012. Subsequently, the hardware and software of SENJU have been checked and confirmed that they worked fine. At the same time, diffraction experiments of several organic and inorganic crystals have been done using NaCl, C12A7, and so on. In these measurements, Bragg reflections in the high-Q region (d-spacing $$<$$ 0.5 ${AA}$) were clearly observed and analyzed successfully. In this presentation, we will show the instrument design and performance evaluation of SENJU in detail.

Journal Articles

Role of magnetic chirality in polarization flip upon a commensurate-incommensurate magnetic phase transition in YMn$$_{2}$$O$$_{5}$$

Wakimoto, Shuichi; Kimura, Hiroyuki*; Sakamoto, Yuma*; Fukunaga, Mamoru*; Noda, Yukio*; Takeda, Masayasu; Kakurai, Kazuhisa

Physical Review B, 88(14), p.140403_1 - 140403_5, 2013/10

 Times Cited Count:17 Percentile:34.43(Materials Science, Multidisciplinary)

Journal Articles

Higgs transition from a magnetic Coulomb liquid to a ferromagnet in Yb$$_{2}$$Ti$$_{2}$$O$$_{7}$$

Chang, L.-J.*; Onoda, Shigeki*; Su, Y.*; Kao, Y.-J.*; Tsuei, K.-D.*; Yasui, Yukio*; Kakurai, Kazuhisa; Lees, M. R.*

Nature Communications (Internet), 3, p.992_1 - 992_7, 2012/08

 Times Cited Count:148 Percentile:2.15(Multidisciplinary Sciences)

Journal Articles

Current status of a time-of-flight single crystal neutron diffractometer SENJU at J-PARC

Tamura, Itaru; Oikawa, Kenichi; Kawasaki, Takuro; Ohara, Takashi; Kaneko, Koji; Kiyanagi, Ryoji; Kimura, Hiroyuki*; Takahashi, Miwako; Kiyotani, Tamiko*; Arai, Masatoshi; et al.

Journal of Physics; Conference Series, 340, p.012040_1 - 012040_4, 2012/02

 Times Cited Count:10 Percentile:4.62

Journal Articles

A Novel technique for monitoring the reproducibility of laser tape-target interactions using an X-ray pinhole camera

Ogura, Koichi; Fukumi, Atsushi*; Li, Z.*; Orimo, Satoshi; Sagisaka, Akito; Nishiuchi, Mamiko; Kado, Masataka; Mori, Michiaki; Yogo, Akifumi; Hayashi, Yukio; et al.

Journal of the Vacuum Society of Japan, 52(10), p.570 - 574, 2009/10

For accurate control of relativistic laser-plasma interaction under the repetitive operation, we have to measure and control the laser irradiation conditions such as laser parameters, the target shooting accuracy and so on as well as measuring proton parameter on each laser shot. The displacement of the laser shooting position on a tape target, that are used in the high energy proton generation using an ultra-short Ti:sapphire laser system, is measured by observing an X-ray image from laser plasma with an X-ray pinhole camera for each laser shot. The displacement of the shooting position on the target is about 20micron and the accuracy of the target positioning is within 20micron which is small enough for present laser focusing optics with an F number of 3.6 (f=179mm). The technique contributes to accurate control of a repetitive laser driven proton accelerators.

Journal Articles

Spin chirality and electric polarization in multiferroic compounds RMn$$_2$$O$$_5$$ ($$R$$ = Ho, Er)

Wakimoto, Shuichi; Kimura, Hiroyuki*; Fukunaga, Mamoru*; Nishihata, Keisuke*; Takeda, Masayasu; Kakurai, Kazuhisa; Noda, Yukio*; Tokura, Yoshinori*

Physica B; Condensed Matter, 404(17), p.2513 - 2516, 2009/09

 Times Cited Count:4 Percentile:76.82(Physics, Condensed Matter)

Journal Articles

Magnetic-field-induced polarization flop in multiferroic TmMn$$_{2}$$O$$_{5}$$

Fukunaga, Mamoru*; Sakamoto, Yuma*; Kimura, Hiroyuki*; Noda, Yukio*; Abe, Nobuyuki*; Taniguchi, Koji*; Arima, Takahisa*; Wakimoto, Shuichi; Takeda, Masayasu; Kakurai, Kazuhisa; et al.

Physical Review Letters, 103(7), p.077204_1 - 077204_4, 2009/08

 Times Cited Count:46 Percentile:12.74(Physics, Multidisciplinary)

Journal Articles

Visualizing rattling in PrOs$$_4$$Sb$$_{12}$$ by single crystal neutron diffraction and maximum-entropy analysis

Kaneko, Koji; Metoki, Naoto; Kimura, Hiroyuki*; Noda, Yukio*; Matsuda, Tatsuma; Kogi, Masafumi*

Journal of the Physical Society of Japan, 78(7), p.074710_1 - 074710_4, 2009/07

 Times Cited Count:18 Percentile:28.79(Physics, Multidisciplinary)

In order to obtain a detailed picture of rattling in PrOs$$_4$$Sb$$_{12}$$, a single crystal neutron diffraction experiment and a maximum-entropy analysis were carried out. At room temperature, a widely distributed anisotropic Pr nuclear density in the Sb icosahedron cage was revealed. An unusual trapezoidal form in the cross-sectional density profile of Pr clearly demonstrates the presence of strong anharmonicity in the Pr potential, in which the $${langle}1,1,1{rangle}$$ direction has the maximum spread. The highest density is found at an off-center position along the same direction. The Pr density distribution becomes isotropic and sharp by cooling down to 8 K. Moreover, the highest density of Pr at 8 K is found at the center of the cage. The obtained nuclear density distribution and its temperature variation indicate that the rattling in PrOs$$_4$$Sb$$_{12}$$ is a strong anharmonic thermal motion without an off-center potential minimum.

Journal Articles

Charge excitations in the stripe-ordered La$$_{5/3}$$Sr$$_{1/3}$$NiO$$_{4}$$ and La$$_{2-x}$$(Ba,Sr)$$_{x}$$CuO$$_{4}$$ superconducting compounds

Wakimoto, Shuichi; Kimura, Hiroyuki*; Ishii, Kenji; Ikeuchi, Kazuhiko; Adachi, Tadashi*; Fujita, Masaki*; Kakurai, Kazuhisa; Koike, Yoji*; Mizuki, Junichiro; Noda, Yukio*; et al.

Physical Review Letters, 102(15), p.157001_1 - 157001_4, 2009/04

 Times Cited Count:24 Percentile:23.19(Physics, Multidisciplinary)

Journal Articles

Magnetic-field-induced magnetic phase transitions associated with ferroelectricity in multiferroic ErMn$$_{2}$$O$$_{5}$$

Kimura, Hiroyuki*; Wakimoto, Shuichi; Fukunaga, Mamoru*; Noda, Yukio*; Kaneko, Koji; Metoki, Naoto; Kakurai, Kazuhisa; Kay, Kohn*

Journal of the Physical Society of Japan, 78(3), p.034718_1 - 034718_5, 2009/03

 Times Cited Count:5 Percentile:60.24(Physics, Multidisciplinary)

Journal Articles

Spiral spin structures and origin of the magnetoelectric coupling in YMn$$_2$$O$$_5$$

Kim, J.-H.*; Lee, S.-H.*; Park, S. I.*; Kenzelmann, M.*; Harris, A. B.*; Schefer, J.*; Chung, J.-H.*; Majkrzak, C. F.*; Takeda, Masayasu; Wakimoto, Shuichi; et al.

Physical Review B, 78(24), p.245115_1 - 245115_10, 2008/12

 Times Cited Count:38 Percentile:18.4(Materials Science, Multidisciplinary)

Journal Articles

The Frontiers of condensed matter science advanced by J-PARC

Fujii, Yasuhiko; Arai, Masatoshi; Kadono, Ryosuke*; Kanaya, Toshiji*; Kamiyama, Takashi*; Niimura, Nobuo*; Nojiri, Hiroyuki*; Noda, Yukio*; Yagi, Takehiko*; Yamada, Kazuyoshi*

Kotai Butsuri, 43(7), p.441 - 450, 2008/07

no abstracts in English

Journal Articles

Strong anharmonicity of Pr thermal vibration in heavy fermion superconductor PrOs$$_4$$Sb$$_{12}$$

Kaneko, Koji; Metoki, Naoto; Kimura, Hiroyuki*; Noda, Yukio*; Matsuda, Tatsuma; Kogi, Masafumi*

Physica B; Condensed Matter, 403(5-9), p.874 - 876, 2008/04

 Times Cited Count:1 Percentile:93.12(Physics, Condensed Matter)

In order to clarify the detailed structure of PrOs$$_{4}$$Sb$$_{12}$$, single crystal neutron diffraction experiments were carried out and obtained data were analyzed by means of the maximum entropy method (MEM). A space- and time-averaged nuclear density distribution reflecting a thermal vibration can be obtained through the MEM analysis. The result unveils a widely spread Pr distribution in the Sb cage at room temperature. The Pr density has a almost flat distribution in the real space centered at the Sb cage, which reaches roughly 0.58${AA}$ in the full width at half maximum (FWHM). These features are far from the simple harmonic model, namely, the present result suggests the strong anharmonicity of the Pr potential in the Sb cage.

Journal Articles

Devil's flower resulting from a successive charge disproportionation of NaV$$_{2}$$O$$_{5}$$; Understanding of the details of the Ising spin and the competitive interactions which made the devil's flower bloom

Owada, Kenji; Fujii, Yasuhiko; Muraoka, Jiro*; Nakao, Hironori*; Murakami, Yoichi*; Noda, Yukio*; Osumi, Hiroyuki*; Ikeda, Naoshi*; Shobu, Takahisa; Isobe, Masahiko*; et al.

Hoshako, 21(2), p.87 - 96, 2008/03

Devil's flower has been found in a temperature-pressure phase diagram of NaV$$_{2}$$O$$_{5}$$, which shows a charge disproportionation (CD) at ambient pressure. By a complementary use of an X-ray structural analysis and a resonant X-ray diffraction, which is sensitive to CD, we have investigated the structural relationship between two ground states appeared in lower and higher pressure regions including the charge arrangements. It has been clarified that two equivalent types of charge arrangement in CD correspond to the Ising variable in NaV$$_{2}$$O$$_{5}$$. The atomic shifts are regarded as linearly coupled to the Ising spins. The results lead us to the conclusion that it is the first time that the devil's flower blooms in a charge-disproportionation system. The results also lead us to a hypothesis that the competitive interactions between a Ising spins may result from the Ising spin-phonon coupling.

Journal Articles

Visualization of anharmonic thermal vibration in filled skutterudite compounds

Kaneko, Koji; Metoki, Naoto; Kimura, Hiroyuki*; Noda, Yukio*; Matsuda, Tatsuma; Kogi, Masafumi*

Journal of the Physical Society of Japan, 77(Suppl.A), p.245 - 247, 2008/00

 Times Cited Count:3 Percentile:70.74(Physics, Multidisciplinary)

In filled skutterudite compounds, the importance of rattling is suggested in connection with the formation of heavy quasiparticles and superconductivity. A combination of the single crystal neutron diffraction and the maximum entropy method (MEM) offers an ability to unveil the thermal motion of Pr in PrOs$$_4$$Sb$$_{12}$$ without any specific model. The result reveals the widely spread Pr nuclear density distribution at room temperature, which has a trapezoidal shape in the real space with the width of roughly 0.6 ${AA}$ in the full width at half maximum. In contrast, the Pr distribution at 8 K has a sharp, isotropic gaussian shape, and the highest density locates at the center of the cage. These features indicate the strong anharmonicity of the Pr potential in the Sb cage.

Journal Articles

Structural relations between two ground states of NaV$$_{2}$$O$$_{5}$$ under high pressure; A Synchrotron X-ray diffraction study

Owada, Kenji; Fujii, Yasuhiko; Muraoka, Jiro*; Nakao, Hironori*; Murakami, Yoichi; Noda, Yukio*; Osumi, Hiroyuki*; Ikeda, Naoshi*; Shobu, Takahisa; Isobe, Masahiko*; et al.

Physical Review B, 76(9), p.094113_1 - 094113_10, 2007/09

 Times Cited Count:10 Percentile:53.04(Materials Science, Multidisciplinary)

Structural relations between two ground states of the ANNNI (Axial Next Nearest Neighbor Ising) compound NaV$$_{2}$$O$$_{5}$$, C$$_{1/4}$$- and C$$_{0}$$-phases below and above the transition pressure $$P_{rm C}$$ = 1 GPa, were investigated by X-ray diffraction and scattering techniques. The structure of the C$$_{0}$$-phase is well explained by the $$A$$($$A'$$) pattern which is one of four layers ($$AAA'A'$$) of the C$$_{1/4}$$-phase, however, the amount of the atomic shifts under the conditions 1.6 GPa and 6 K is 27% that under ambient pressure. On the other hand, resonant X-ray scattering showed that the charges are disproportionated under high pressure. Based on these facts, it was concluded that charge disproportionation corresponds to the Ising variable in NaV$$_{2}$$O$$_{5}$$, where the atomic shifts are regarded as linearly coupled to the Ising spins. These results lead to the hypothesis that the competitive interactions between the Ising spins may result from the Ising spin-phonon coupling.

Journal Articles

Characterization of an intense laser-produced preformed plasma for proton generation

Sagisaka, Akito; Daido, Hiroyuki; Ogura, Koichi; Orimo, Satoshi; Hayashi, Yukio; Mori, Michiaki; Nishiuchi, Mamiko; Yogo, Akifumi; Kado, Masataka; Fukumi, Atsushi*; et al.

Journal of the Korean Physical Society, 51(1), p.442 - 446, 2007/07

 Times Cited Count:1 Percentile:88.41(Physics, Multidisciplinary)

The recent progress of the laser driven accelerators which include high power laser driven electrons and ions are reviewed. The studies at JAEA Kansai are mainly described. Based on the recent progres, the various aspects of the applications are also reviewed.

Journal Articles

High quality laser-produced proton beam generation by phase rotation

Noda, Akira*; Nakamura, Shu*; Iwashita, Yoshihisa*; Shirai, Toshiyuki*; Tongu, Hiromu*; Soda, Hikaru*; Daido, Hiroyuki; Mori, Michiaki; Kado, Masataka; Sagisaka, Akito; et al.

International Journal of Modern Physics B, 21(3&4), p.319 - 330, 2007/02

Laser ion production has been studied for downsizing of the accelerator dedicated for cancer therapy. For optimization of various parameters such as pre-pulse condition, target position, laser spot size on target, laser pulse width and so on, time of flight (TOF) measurement utilizing the detected signal by a plastic scintillation counter played an essential role for real time measurement. Protons up to 900 keV and 600 keV are produced from the thin foil targets of Ti 3 micron and 5 micron in thickness, respectively. Modification of the energy distribution of the laser-produced ions with Maxwell distribution by utilizing an RF electric field synchronized to the pulse laser, which is the rotation of the ion beam in the longitudinal phase space (phase rotation), has been demonstrated for the first time.

Journal Articles

Magnetically induced ferroelectricity in multiferroic compounds of $$R$$Mn$$_2$$O$$_5$$

Kimura, Hiroyuki*; Kobayashi, Satoru*; Wakimoto, Shuichi; Noda, Yukio*; Kon, Keiichiro*

Ferroelectrics, 354, p.77 - 85, 2007/01

 Times Cited Count:21 Percentile:32.55(Materials Science, Multidisciplinary)

A review is given on the studies of magnetic properties and dielectric properties as functions of temperature and magnetic field for various multiferroic $$R$$Mn$$_2$$O$$_5$$ ($$R$$ = rare-earth) compounds. We have observed successive dielectric and magnetic phase transitions which concomitantly take place and a so-called multiferroics is realized. In this system, the ferroelectricity is magnetically induced and the commensurate magnetism is indispensable to produce a spontaneous electric polarization. The microscopic origin of the magnetically induced ferroelectricity and the role of the rare-earth magnetic moment for a colossal magnetoelectric effect in $$R$$Mn$$_2$$O$$_5$$ will be discussed in the viewpoint of the magnetic structure.

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