Electronic structure of lithium amide

Kamakura, Nozomu; Takeda, Yukiharu; Saito, Yuji; Yamagami, Hiroshi; Tsubota, Masami*; Paik, B.*; Ichikawa, Takayuki*; Kojima, Yoshitsugu*; Muro, Takayuki*; Kato, Yukako*; et al.

Physical Review B, 83(3), p.033103_1 - 033103_4, 2011/01

https://doi.org/10.1103/PhysRevB.83.033103

The electronic structure of lithium amide, which is lightweight complex hydride expected as a high-capacity hydrogen storage material, is investigated by N 1 soft X-ray emission spectroscopy (XES) and absorption spectroscopy (XAS). The overall feature of the electronic structure of lithium amide by the XES and XAS is consistent with the band calculation, while the strongly hybridized state with H 1 is located at higher binding energy than the band calculation.

Momentum-resolved charge excitations in high- cuprates studied by resonant inelastic X-ray scattering

Ishii, Kenji; Hoesch, M.*; Inami, Toshiya; Kuzushita, Kaori*; Owada, Kenji; Tsubota, Masami; Murakami, Yoichi; Mizuki, Junichiro; Endo, Yasuo; Tsutsui, Kenji*; et al.

Journal of Physics and Chemistry of Solids, 69(12), p.3118 - 3124, 2008/12

https://doi.org/10.1016/j.jpcs.2008.06.041

Resonant X-ray scattering of PrRuP

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

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.e178 - e180, 2007/03

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.

Induced orbital polarization of Ga ligand atoms in UGa (=Ni, Pd, and Pt)

Kuzushita, Kaori*; Ishii, Kenji; Wilkins, S. B.*; Janousova, B.*; Inami, Toshiya; Owada, Kenji; Tsubota, Masami; Murakami, Yoichi; Kaneko, Koji; Metoki, Naoto; et al.

Physical Review B, 73(10), p.104431_1 - 104431_5, 2006/03

https://doi.org/10.1103/PhysRevB.73.104431

We report a resonant X-ray scattering study of antiferromagnetic uranium compounds UGa (=Ni, Pd, and Pt) at the Ga -edge. A large resonant signal is observed below the Nel temperatures. The azimuth dependence in both - and - polarization channels establishes that the resonant signal has the symmetry of the magnetic dipole. This resonance with the band electrons is interpreted within a semi-localized model as an orbital polarization of the Ga states induced through strong hybridization with U valence level. These results demonstrate that resonant magnetic X-ray scattering at the anions, taken in combination with symmetry arguments, can be used to determine the configuration of the U moments and provide information about the hybridization.

Magnetic-field-induced transition in the lattice modulation of colossal magnetoelectric GdMnO and TbMnO compounds

Arima, Takahisa*; Goto, Tsuyoshi*; Yamazaki, Yuichi*; Miyasaka, Shigeki*; Ishii, Kenji; Tsubota, Masami; Inami, Toshiya; Murakami, Yoichi*; Tokura, Yoshinori*

Physical Review B, 72(10), p.100102_1 - 100102_4, 2005/09

https://doi.org/10.1103/PhysRevB.72.100102

Single-crystal synchrotron X-ray diffraction measurements in strong magnetic fields have been performed for magnetoelectric compounds GdMnO and TbMnO. It has been found that the //a ferroelectric phase induced by the application of a magnetic field at low temperatures is characterized by commensurate lattice modulation along the orthorhombic axis with q=1/2 and q=1/4. The lattice modulation is ascribed to antiferromagnetic spin alignment with a modulation vector of (0 1/4 1). The change of the spin structure is directly correlated with the magnetic-field-induced electric phase transition, because any commensurate spin modulation with (0 1/4 1) should break glide planes normal to the axis of the distorted perovskite with the space group.

Search for orbital excitation in YTiO by neutron scattering

Shamoto, Shinichi; Tsubota, Masami*; Iga, Fumitoshi*; Fk, B.*; Kajitani, Tsuyoshi*

Journal of Neutron Research, 13(1-3), p.175 - 178, 2005/03

https://doi.org/10.1080/10238160412331299951

YTiO with T~30 K has been studied by the MARI spectrometer with E=130 meV and 500 meV at T=5 K, 40K, and 200 K. We have not found any clear orbital excitation in a wide Q-E range (0.5Q25, 6E350 meV). The intensity of orbital excitation would be significantly weak in comparison with the phonon.

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.

Pressure-induced phase separation with intersite hydrogen transfer in rare-earth metal hydrides

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

no journal, , 

Rare-earth metal La forms T-site occupied fcc-LaH and fully occupied fcc-LaH, the former is metallic and the latter is insulating. Our previous synchrotron X-ray and infrared measurements revealed that the dihydride decomposed into hydrogen-rich and hydrogen-poor phases upon compression to 11 GPa at ambient temperature; the hydrogen rich phase was identified as LaH but the hydrogen composition and occupation sites of the hydrogen-poor phase remained undetermined. The crystal structure of the hydrogen-poor phase was investigated for LaD by neutron diffraction measurement with a total diffractometer NOVA at J-PARC. The formation of NaCl-type LaD as a counterpart of LaD by the decomposition was confirmed from the diffraction profiles. First-principle enthalpy and lattice dynamic calculations have demonstrated that the NaCl-type LaH is stabilized at high pressures.

Tetragonal distortion and successive disproportionation reaction of fcc lanthanum dihydride under high pressure

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

no journal, , 

We have investigated the structural properties of rare-earth metal hydrides under high pressure. LaH has the CaF type structure in which the H atoms locate at the tetrahedral interstitial sites (T-sites) of the fcc metal lattice. Synchrotron radiation X-ray diffraction and infrared reflection experiments revealed disproportionation reaction of LaH into the H-poor and H-rich phases around 11 GPa. Before the disproportionation reaction, we have found that the fcc metal lattice transformed into tetragonal lattice. The ordering of the H atoms in the octahedral-sites (O-sites) causes the tetragonal distortion of LaH. The tetragonal transformation and successive disproportionation reaction of LaH would closely relate to the inter-site transfer of the H atoms between the T- and O-sites. We have performed the neutron diffraction experiments of LaD to investigate the change of the positions and occupancies of the hydrogen atoms under high pressure.

An X-ray diffraction experiment of the magnetization plateau phase of CdCrO

Inami, Toshiya; Owada, Kenji; Tsubota, Masami; Matsuda, Yasuhiro*; Nojiri, Hiroyuki*; Ueda, Hiroaki*

no journal, , 

no abstracts in English