Formation of NaCl-type monodeuteride LaD by the disproportionation reaction of LaD

Machida, Akihiko; Honda, Mitsunori*; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Komatsu, Kazuki*; Arima, Hiroshi*; Oshita, Hidetoshi*; et al.

Physical Review Letters, 108(20), p.205501_1 - 205501_5, 2012/05

https://doi.org/10.1103/PhysRevLett.108.205501

Hydrogen atoms absorbed in a metal occupy the interstitial sites of the metal lattice. In an fcc metal lattice, each metal atom has two tetrahedral (T) and one octahedral (O) sites that can accommodate hydrogen. Rare-earth metal La forms T-site occupied LaH and fully occupied LaH. O-site occupied or NaCl-type monohydride has yet to be reported for rare-earth metals. Previous X-ray diffraction measurements revealed the pressure-induced decomposition of an fcc-LaH into H-rich and H-poor phases around 11 GPa. The present neutron diffraction measurements on LaD confirm the formation of NaCl-type LaD as a counterpart of the D-rich LaD by disproportionation. First-principle calculations demonstrate that the NaCl-type LaH is stabilized at high pressures. Finding the NaCl-type LaH will pave the way for investigations on the site-dependent nature of hydrogen-metal interactions.

Effect of hydrogenation on the electronic state of metallic La hydrides probed by X-ray absorption sectroscopy at the La -edges

Ishimatsu, Naoki*; Sasada, Ryohei*; Maruyama, Hiroshi*; Ichikawa, Takayuki*; Miyaoka, Hiroki*; Kimura, Toru*; Tsubota, Masami*; Kojima, Yoshitsugu*; Tsumuraya, Takao*; Oguchi, Tamio*; et al.

Journal of Physics; Conference Series, 190, p.012070_1 - 012070_4, 2009/11

https://doi.org/10.1088/1742-6596/190/1/012070

We have investigated the effect of hydrogenation on La and electronic states in metallic LaH by X-ray absorption near edge structure at the La -edges. As the hydrogen content increases from 0 to 2.6, white-line intensity at the La -edges shows a remarkable increase in the range of 2.0. This is interpreted as the increase in La hole induced by interstitial H atoms on the octahedral sites. On the other hand, the shoulder structure at the La -edge disappears in the process of = 0.0 2.0, indicating that the - hybridization is weakened by H atoms on the tetrahedral sites. This study demonstrates that H atoms on the two interstitial H sites provide different contribution to the modification of the electronic states.

Direct observation of field-induced variant transformation in FePt using pulsed magnetic field X-ray diffraction

Ouyang, Z. W.*; Matsuda, Yasuhiro*; Nojiri, Hiroyuki*; Inami, Toshiya; Owada, Kenji; Tsubota, Masami*; Sakon, Takuo*; Fukuda, Takashi*; Kakeshita, Tomoyuki*

Journal of Applied Physics, 102(11), p.113917_1 - 113917_6, 2007/12

https://doi.org/10.1063/1.2822278

Doping Momentum dependence of charge dynamics in NdCeCuO (x=0, 0.075, and 0.15) studied by Resonant inelastic X-ray scattering

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Maekawa, Sadamichi*; Hoesch, M.; Kuzushita, Kaori; Inami, Toshiya; Tsubota, Masami; Yamada, Kazuyoshi*; et al.

AIP Conference Proceedings 850, p.403 - 404, 2006/09

https://doi.org/10.1063/1.2354756

We report a resonant inelastic X-ray scattering (RIXS) study of charge excitations in the electron-doped high- superconductor NdCeCuO. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with -dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

Quest for the high-filed phase of CdCrO using an X-ray diffraction technique

Inami, Toshiya; Owada, Kenji; Tsubota, Masami; Murata, Yuto*; Matsuda, Yasuhiro*; Nojiri, Hiroyuki*; Ueda, Hiroaki*; Murakami, Yoichi*

Journal of Physics; Conference Series, 51, p.502 - 505, 2006/00

https://doi.org/10.1088/1742-6596/51/1/114

no abstracts in English

Momentum dependence of charge excitations in the electron-doped superconductor NdCeCuO; A Resonant inelastic X-ray scattering study

Ishii, Kenji; Tsutsui, Kenji*; Endo, Yasuo*; Toyama, Takami*; Maekawa, Sadamichi*; Hoesch, M.; Kuzushita, Kaori; Tsubota, Masami; Inami, Toshiya; Mizuki, Junichiro; et al.

Physical Review Letters, 94(20), p.207003_1 - 207003_4, 2005/05

https://doi.org/10.1103/PhysRevLett.94.207003

We report a resonant inelastic X-ray scattering (RIXS) study of charge excitations in the electron-doped high- superconductor NdCeCuO. The intraband and interband excitations across the Fermi energy are separated for the first time by tuning the experimental conditions properly to measure charge excitations at low energy. A dispersion relation with -dependent width emerges clearly in the intraband excitation, while the intensity of the interband excitation is concentrated around 2 eV near the zone center. The experimental results are consistent with theoretical calculation of the RIXS spectra based on the Hubbard model.

Structural study of superionic AgGeSe glasses

Kawakita, Yukinobu; Otomo, Toshiya*; Ueno, Hiroki; Tsubota, Masami*; Kumara, L. S. R.*; Oshita, Hidetoshi*; Suzuya, Kentaro; Takeda, Shinichi*

no journal, , 

Superionic glasses have attracted widespread interest in relation with their potential application as solid electrolytes in new devices. The interest in Ag(GeSe) ternary alloys derives from extensive compositional range of glass forming and rapid increase in conductivity at . Neutron diffraction measurements of Ag(GeSe) glass have been performed over a wide Q range by utilizing the total neutron scattering instrument, NOVA, installed at BL21 in MLF, J-PARC. Since Ag is a good neutron absorber, NOVA instrument and method for data reduction can be examined by this sample. Structural model of this material has already been proposed by reverse Monte Carlo simulation based on experimental structural data. This structure model has been checked in consistency with new data in an extremely wide Q range. This work was supported by NEDO under "Advanced Fundamental Research Project on Hydrogen Storage Materials" (HydroStar).

Resonant X-ray scattering of PrRuP

Ishii, Kenji; Tsubota, Masami; Inami, Toshiya; Tsutsui, Satoshi*; Hao, L.*; Hasegawa, Tomoo*; Iwasa, Kazuaki*; Murakami, Yoichi; Sugawara, Hitoshi*; Saha, S. R.*; et al.

no journal, , 

PrRuP shows a metal-insulator (MI) transition at 62 K accompanied by a structural phase transition. Because LaRuP without electrons does not shows the MI transition, electrons in the Pr atom plays an important role in the transition. In order to elucidate a modulation of electronic states of Pr, we have carried out a resonant X-ray scattering study of PrRuP at Pr - and -edges. Below , resonant signal at the absorption main-edge was successfully observed at the superlattice reflections of the modulation vector in addition to the energy-independent component from the lattice distortion. Because the reflection contains the difference of anomalous scattering factors between two Pr atoms in the unit cell, two different electronic states are actually ordered below . Furthermore we found that the polarization of X-ray is mostly unrotated even at the resonance, which indicates that the resonant scattering in PrRuP is almost isotropic.

X-ray and neutron diffraction studies of pressure-induced phase separation of LaD

Machida, Akihiko; Honda, Mitsunori; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Komatsu, Kazuki*; Arima, Hiroshi; Oshita, Hidetoshi*; et al.

no journal, , 

We have investigated the pressure-induced phase separation in rare-earth metal dihydrides by synchrotron radiation X-ray diffraction and neutron diffraction experiments. Rare-earth metal hydrides exhibit the stoichiometoric dihydride and trihydride. The dihydride is a metallic while trihydride is an insulator. Recently, we have found the pressure induced phase separation in the lanthanum dihydride. This phenomenon is understood as the decomposition into the hydrogen-poor and rich phases under high pressure. However, the hydrogen occupancy and position have been unclear yet. Our neutron diffraction experiments have revealed that an NaCl-type mono-deuteride is formed as a counterpart of the deuterium-rich phase.

Formation of NaCl-type lanthanum monodeuteride under high pressure

Machida, Akihiko; Honda, Mitsunori*; Hattori, Takanori; Sano, Asami; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi; Komatsu, Kazuki*; Arima, Hiroshi*; Oshita, Hidetoshi*; et al.

no journal, , 

Hydrogen atoms absorbed in a metal occupy the interstitial sites of the metal lattice. In an fcc metal lattice, each metal atom has two tetrahedral (T) and one octahedral (O) sites that can accommodate hydrogen. Rare-earth metal La forms T-site occupied LaH and fully occupied LaH. Previous X-ray diffraction measurements revealed the pressure-induced decomposition of an fcc-LaH into H-rich and H-poor phases around 11 GPa. We performed the neutron diffraction measurements on LaD, and found the formation of NaCl-type LaD as a phase separation products. We have first found the NaCl-type rare-earth metal monohydride.