Torigoe, Shuhei*; Ishimoto, Yutaro*; Aoishi, Yuhei*; Murakawa, Hiroshi*; Matsumura, Daiju; Yoshii, Kenji; Yoneda, Yasuhiro; Nishihata, Yasuo; Kodama, Katsuaki; Tomiyasu, Keisuke*; et al.
Physical Review B, 93(8), p.085109_1 - 085109_5, 2016/02
Matsuoka, Takehiro*; Hirao, Naohisa*; Oishi, Yasuo*; Shimizu, Katsuya*; Machida, Akihiko; Aoki, Katsutoshi
Koatsuryoku No Kagaku To Gijutsu, 21(3), p.190 - 196, 2011/09
We present the newly developed electrical resistance measurement technique for metal hydrides compressed in high-pressure H and the first successful simultaneous measurements of electrical resistance and X-ray diffraction of FeH at high pressures and low temperatures. The electrical resistivity showed a sharp increase with the formation of iron-hydride FeH () at 3.5 GPa. The '-phase of FeH was found to be metallic up to 25.5 GPa. The vs. curves up to 16.5 GPa approximately follow Fermi-liquid law below 25 K. However, was found to be better fitting at 25.5 GPa. This change can be related to the previously reported ferromagnetism collapse at corresponding pressures.
Matsuoka, Takahiro*; Fujihisa, Hiroshi*; Hirao, Naohisa*; Oishi, Yasuo*; Mitsui, Takaya; Masuda, Ryo; Seto, Makoto*; Yoda, Yoshitaka*; Shimizu, Katsuya*; Machida, Akihiko; et al.
Physical Review Letters, 107(2), p.025501_1 - 025501_4, 2011/07
Europium-hydride EuH exposed to high-pressure H conditions has been found to exhibit structural and valence changes, (=2, divalent) 63/ (=2, 7.2-8.7 GPa) 4/ (2, 8.7-9.7 GPa) 4/ (2, 9.7 GPa-, trivalent). Having trivalent character and distorted cubic fcc structure, the 4/ structure is the -phase which has been commonly observed for other rare-earth metal hydrides. Our study clearly demonstrates that EuH is no longer an "irregular" member of the rare earth metal hydrides.
Setoodehnia, K.*; Chen, A. A.*; Komatsubara, Tetsuro*; Kubono, Shigeru*; Binh, D. N.*; Carpino, J. F.*; Chen, J.*; Hashimoto, Takashi*; Hayakawa, Takehito; Ishibashi, Yoko*; et al.
Physical Review C, 83(1), p.018803_1 - 018803_4, 2011/01
The structure of proton-unbound S states strongly determines the thermonuclear P(, )S reaction rate at temperatures characteristic of explosive hydrogen burning in classical novae and type I X-ray bursts. Specifically, the rate had been previously predicted to be dominated by two low-lying, unobserved, levels in the =4.7-4.8 MeV region, with spin and parity assignments of 3 and 2. In recent experimental work, two candidate levels were observed with energies of 4.699 MeV and 4.814 MeV, but no experimental information on their spins and parities was obtained. We have performed an in-beam -ray spectroscopy study of S with the Si(He, )S reaction. The spin and parities were inferred from a comparison to the known decay schemes of the corresponding mirror states.
Mitsui, Takaya; Seto, Makoto; Hirao, Naohisa*; Oishi, Yasuo*; Kobayashi, Yasuhiro*; Higashitaniguchi, Satoshi*; Masuda, Ryo*
Japanese Journal of Applied Physics, Part 2, 46(16), p.L382 - L384, 2007/04
Energy-domain synchrotron radiation Mssbauer spectroscopy was performed by a single-line Mssbauer filtering technique and focusing X-ray optics. Pure nuclear Bragg reflection from a heated FeBO single crystal was used for a neV order bandwidth ultrahigh energy resolution X-ray analyzer. As an example of small target research, the Mssbauer transmission spectrum of polycrystalline iron metal was observed using a diamond anvil cell at multimegabar pressures (252 GPa) for the first time.
Mitsui, Takaya; Seto, Makoto; Kikuta, Seishi*; Hirao, Naohisa*; Oishi, Yasuo*; Takei, Fumihiko*; Kobayashi, Yasuhiro*; Kitao, Shinji*; Higashitaniguchi, Satoshi*; Masuda, Ryo*
Japanese Journal of Applied Physics, Part 1, 46(2), p.821 - 825, 2007/02
Ultrahigh monochromatic 14.4 keV X-rays with a narrow bandwidth of 15.4 neV were generated successfully with a high counting rate of 12,000 counts/s at the undulator beamline (BL11XU) of SPring-8. It was achieved by combining an intense X-ray from the third generation synchrotron radiation facility SPring-8 and pure nuclear Bragg scattering of a very highquality FeBO perfect single crystal at the Nel temperature. We describe the detailed study of the beam characteristics and some performance test experiments of energy-domain synchrotron radiation Mssbauer spectroscopy, including a highpressure experiment using a diamond anvil cel.
Matsuoka, Takehiro*; Kitayama, Takayasu*; Shimizu, Katsuya*; Nakamoto, Yuki*; Kagayama, Tomoko*; Aoki, Katsutoshi; Oishi, Yasuo*; Takemura, Kenichi*
High Pressure Research, 26(4), p.391 - 394, 2006/12
The electrical and structural properties of yttrium hydride YHx was studied by the in-situ measurements of the electrical resistance and X-ray diffraction up to 86 GPa. The electrical resistivity increased with applying pressure up to 10 GPa and showed a maximum which accompanied with the structural transition of metal lattice from hcp to fcc structure. In fcc phase the resistivity decreased significantly, however the value still remained larger by 4 orders of magnitude that that of pure yttrium metal. We could not confirm the insulator to metal transition up to 23 GPa. The resistivity showed another maximum in the large pressure region 40 60 GPa without the structural phase transition of metal lattice.
Owada, Kenji; Ishii, Kenji; Inami, Toshiya; Murakami, Yoichi; Shobu, Takahisa*; Osumi, Hiroyuki*; Ikeda, Naoshi*; Oishi, Yasuo*
Physical Review B, 72(1), p.014123_1 - 014123_10, 2005/07
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 (CHNH)CuCl. We have found a structural phase transition at Pc=4 GPa. 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. 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 CuCl octahedron. The 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 Cu ion markedly changes. Two possible structures above Pc are proposed.
Kohara, Shinji*; Oishi, Yasuo*; Takata, Masaki*; Yoneda, Yasuhiro; Suzuya, Kentaro
Nihon Kessho Gakkai-Shi, 47(2), p.123 - 129, 2005/04
The use of high-energy (E 50 keV) X-rays from SPring-8 allows us to perform X-ray diffraction experiments on disordered materials with the following advantages: high resolution in real space due to the wide range of scattering vector, small correction terms (particularly the absorption correction), and fast diffraction measurement with small amount of samples. Recently, high-energy X-ray diffraction data have been combined with neutron diffraction data from a pulsed neutron source to provide more detailed and reliable structural information than has hitherto been available. Furthermore, the use of reverse Monte Carlo modelling and PDF (pair distribution function) simulation based on high-energy X-ray diffraction data have succeeded in illustrating 3-dimensional structure of disordered materials and disorder in crystalline materials.
Fuchizaki, Kazuhiro*; Fujii, Yasuhiko*; Oishi, Yasuo*; Omura, Ayako*; Hamaya, Nozomu*; Katayama, Yoshinori; Okada, Taku
Journal of Chemical Physics, 120(23), p.11196 - 11199, 2004/06
The location of the liquidus in the low-pressure crystalline phase of SnI was determined utilizing X-ray diffraction measurements under pressures up to approximately GPa. The liquidus is not well fitted to a monotonically increasing curve such as Simon's equation, but breaks near GPa and then becomes almost flat. The results are compared to those from molecular dynamics simulations. Ways to improve the model potential adopted in the simulations are discussed.
Isshiki, Maiko*; Irifune, Tetsuo*; Hirose, Kei*; Ono, Shigeaki*; Oishi, Yasuo*; Watanuki, Tetsu; Nishibori, Eiji*; Takata, Masaki*; Sakata, Makoto*
Nature, 427(6969), p.60 - 63, 2004/01
no abstracts in English
Jarrige, I.; Rueff, J.-P.*; Shieh, S.*; Taguchi, Munetaka*; Oishi, Yasuo*; Matsumura, Takashi*; Ishii, Hirofumi*; Hiraoka, Nozomu*; Cai, Y.*
no journal, ,
Jarrige, I.; Rueff, J.-P.*; Shieh, S.*; Taguchi, Munetaka*; Oishi, Yasuo*; Matsumura, Takeshi*; Ishii, Hirofumi*; Hiraoka, Nozomu*; Cai, Y. Q.*
no journal, ,
Matsuoka, Takehiro*; Shimizu, Katsuya*; Fujihisa, Hiroshi*; Hirao, Naohisa*; Oishi, Yasuo*; Yoda, Yoshitaka*; Mitsui, Takaya; Masuda, Ryo; Machida, Akihiko; Aoki, Katsutoshi; et al.
no journal, ,
Europium-hydride EuH exposed to high-pressure H conditions has been studied by X-ray diffraction and Mssbauer spectroscopy measurements up to 50 GPa using synchrotron radiation. We report new structural and valence transitions, Pnma(x=2, divalent) P63/mmc(x=2, 7.2-8.7GPa) I4/m(x2, 8.7-9.7 GPa) I4/mmm(x2, 9.7 GPa, trivalent). The phase of I4/mmm having trivalent character is a small distortion from cubic fcc structure which has been commonly observed for -phase of all other trivalent rare-earth metal hydrides. Our study clearly demonstrates the first observation of -phase of EuH and suggest that the material is no longer an irregular member of the rare earth metal hydrides RH systems.