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Journal Articles

Observation of all-in type tetrahedral displacements in nonmagnetic pyrochlore niobates

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

 Times Cited Count:4 Percentile:26.78(Materials Science, Multidisciplinary)

Journal Articles

Electrical resistance measurement techniques for metal hydrides under high-pressure H$$_2$$ conditions & electrical transport and structural properties of FeH$$_x$$

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$$_2$$ and the first successful ${it in-situ}$ simultaneous measurements of electrical resistance and X-ray diffraction of FeH at high pressures and low temperatures. The electrical resistivity $$rho$$ showed a sharp increase with the formation of iron-hydride FeH$$_x$$ ($$xsim1$$) at 3.5 GPa. The $$epsilon$$'-phase of FeH was found to be metallic up to 25.5 GPa. The $$rho$$ vs. $$T$$ curves up to 16.5 GPa approximately follow Fermi-liquid law below 25 K. However, $$T^5$$ was found to be better fitting at 25.5 GPa. This change can be related to the previously reported ferromagnetism collapse at corresponding pressures.

Journal Articles

Structural and valence changes of europium hydride induced by application of high-pressure H$$_{2}$$

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

 Times Cited Count:24 Percentile:77.07(Physics, Multidisciplinary)

Europium-hydride EuH$$_{x}$$ exposed to high-pressure H$$_{2}$$ conditions has been found to exhibit structural and valence changes, $$Pnma$$ ($$x$$=2, divalent) $$rightarrow$$ $$P$$63/$$mmc$$ ($$x$$=2, 7.2-8.7 GPa) $$rightarrow$$ $$I$$4/$$m$$ ($$x$$$$>$$2, 8.7-9.7 GPa) $$rightarrow$$ $$I$$4/$$mmm$$ ($$x$$$$>$$2, 9.7 GPa-, trivalent). Having trivalent character and distorted cubic fcc structure, the $$I$$4/$$mmm$$ structure is the $$beta$$-phase which has been commonly observed for other rare-earth metal hydrides. Our study clearly demonstrates that EuH$$_{x}$$ is no longer an "irregular" member of the rare earth metal hydrides.

Journal Articles

Spins and parities of astrophysically important $$^{30}$$S states from $$^{28}$$Si($$^{3}$$He, $$n$$$$gamma$$)$$^{30}$$S

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

 Times Cited Count:12 Percentile:64.3(Physics, Nuclear)

The structure of proton-unbound $$^{30}$$S states strongly determines the thermonuclear $$^{29}$$P($$p$$, $$gamma$$)$$^{30}$$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 $$E$$$$_{x}$$=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 $$gamma$$-ray spectroscopy study of $$^{30}$$S with the $$^{28}$$Si($$^{3}$$He, $$n$$$$gamma$$)$$^{30}$$S reaction. The spin and parities were inferred from a comparison to the known decay schemes of the corresponding mirror states.

Journal Articles

Ultrahigh-pressure measurement in the multimegabar range by energy-domain synchrotron radiation $$^{57}$$Fe-M$"o$ssbauer spectroscopy using focused X-rays

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

 Times Cited Count:10 Percentile:41.17(Physics, Applied)

Energy-domain synchrotron radiation M$"o$ssbauer spectroscopy was performed by a single-line M$"o$ssbauer filtering technique and focusing X-ray optics. Pure nuclear Bragg reflection from a heated $$^{57}$$FeBO$$_{3}$$ single crystal was used for a neV order bandwidth ultrahigh energy resolution X-ray analyzer. As an example of small target research, the M$"o$ssbauer transmission spectrum of polycrystalline iron metal was observed using a diamond anvil cell at multimegabar pressures (252 GPa) for the first time.

Journal Articles

Generation and application of ultrahigh monochromatic X-ray using high-quality $$^{57}$$FeBO$$_{3}$$ single crystal

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

 Times Cited Count:27 Percentile:71.15(Physics, Applied)

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 $$^{57}$$FeBO$$_{3}$$ perfect single crystal at the N$'e$el temperature. We describe the detailed study of the beam characteristics and some performance test experiments of energy-domain synchrotron radiation M$"o$ssbauer spectroscopy, including a highpressure experiment using a diamond anvil cel.

Journal Articles

Electrical and structural properties of YH$$_{x}$$(${it x}$ $$sim$$3) under high pressure

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

 Times Cited Count:1 Percentile:11.54(Physics, Multidisciplinary)

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 $$sim$$ 60 GPa without the structural phase transition of metal lattice.

Journal Articles

Structural properties and phase transition of hole-orbital-ordered (C$$_{2}$$H$$_{5}$$NH$$_{3}$$)$$_{2}$$CuCl$$_{4}$$ studied by resonant and non-resonant X-ray scatterings under high pressure

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

 Times Cited Count:23 Percentile:67.58(Materials Science, Multidisciplinary)

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 (C$$_{2}$$H$$_{5}$$NH$$_{3}$$)$$_{2}$$CuCl$$_{4}$$. 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$$_{6}$$ 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$$^{2+}$$ ion markedly changes. Two possible structures above Pc are proposed.

Journal Articles

The Disordered 3-dimensional structure visualized by a combination of high-energy synchrotron X-rays and computer simulations

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.

Journal Articles

Determination of low-pressure crystalline-liquid phase boundary of SnI$$_{4}$$

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

 Times Cited Count:22 Percentile:60.14(Chemistry, Physical)

The location of the liquidus in the low-pressure crystalline phase of SnI$$_{4}$$ was determined utilizing ${it in-situ}$ X-ray diffraction measurements under pressures up to approximately $$3.5$$ GPa. The liquidus is not well fitted to a monotonically increasing curve such as Simon's equation, but breaks near $$1.5$$ 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.

Journal Articles

Stability of magnesite and its high-pressure form in the lowermost mantle

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

 Times Cited Count:205 Percentile:96.47(Multidisciplinary Sciences)

no abstracts in English

Oral presentation

Volume collapse transition in TmTe; Competition between strong correlation and $$f$$-$$d$$ hybridization at high pressure

Jarrige, I.; Rueff, J.-P.*; Shieh, S.*; Taguchi, Munetaka*; Oishi, Yasuo*; Matsumura, Takashi*; Ishii, Hirofumi*; Hiraoka, Nozomu*; Cai, Y.*

no journal, , 

Oral presentation

Single-channel vs multi-channel Kondo effects; SmTe and TmTe studied via resonant inelastic X-ray scattering under high pressure

Jarrige, I.; Rueff, J.-P.*; Shieh, S.*; Taguchi, Munetaka*; Oishi, Yasuo*; Matsumura, Takeshi*; Ishii, Hirofumi*; Hiraoka, Nozomu*; Cai, Y. Q.*

no journal, , 

Oral presentation

Structural and valence changes of europium hydride induced by application of high-pressure H$$_{2}$$

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$$_{x}$$ exposed to high-pressure H$$_{2}$$ conditions has been studied by X-ray diffraction and M$"o$ssbauer spectroscopy measurements up to 50 GPa using synchrotron radiation. We report new structural and valence transitions, Pnma(x=2, divalent) $$rightarrow$$ P63/mmc(x=2, 7.2-8.7GPa) $$rightarrow$$ I4/m(x$$>$$2, 8.7-9.7 GPa) $$rightarrow$$ I4/mmm(x$$>$$2, 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 $$beta$$-phase of all other trivalent rare-earth metal hydrides. Our study clearly demonstrates the first observation of $$beta$$-phase of EuH$$_{x}$$ and suggest that the material is no longer an irregular member of the rare earth metal hydrides RH$$_{x}$$ systems.

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