Browsing by Author "Takahashi, H"

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    Derivation of inter-atomic force constants of Cu2O from diffuse neutron scattering measurement
    (Atom Indonesia, 2013-04-15) Makhsun, T; Sakuma, T; Kartini, E; Takahashi, H; Igawa, N; Danilkin, SA; Sakai, R
    Neutron scattering intensity from Cu2O compound has been measured at 10 K and 295 K with High Resolution Powder Diffractometer at JRR-3 JAEA. The oscillatory diffuse scattering related to correlations among thermal displacements of atoms was observed at 295 K. The correlation parameters were determined from the observed diffuse scattering intensity at 10 and 295 K. The force constants between the neighboring atoms in Cu2O were estimated from the correlation parameters and compared to those of Ag2O. (c) 2016 Atom Indonesia.
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    Estimation of force constants of Al from diffuse neutron scattering measurement
    (The Physical Society of Japan, 2014-06-19) Makhsun; Hashimoto, T; Takahashi, H; Kamishima, O; Igawa, N; Danilkin, SA; Sakuma, T
    Neutron diffraction measurement of an aluminum powder sample at 290 K was carried out at the high resolution powder diffractometer installed at JRR-3. Broad oscillations of the diffuse scattering intensity were observed and explained by the correlation effects among the thermal displacements of atoms. The interatomic force constants were determined from the correlation effects using a newly introduced equation. The derived force constants and the crystal structure of Al were used to estimate the phonon dispersion relations, phonon density of states, and specific heat by computer simulation. The calculated phonon dispersion relations and specific heat of Al are similar to those obtained from inelastic neutron scattering and specific heat measurements, respectively.© 2014, The Physical Society of Japan.
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    Inter-atomic force constants of Ag2O from diffuse neutron scattering measurement
    (Elsevier Science BV., 2012-10-04) Wada, T; Sakuma, T; Sakai, R; Uehara, H; Xianglian; Takahashi, H; Kamishima, O; Igawa, N; Danilkin, SA
    Diffuse neutron scattering measurements have been performed on powder Ag(2)O at 8 and 295 K with the use of High Resolution Powder Diffractometer installed at JRR-3 in Japan Atomic Energy Agency. Oscillatory diffuse scattering intensities are clearly observed at 8 and 295 K. The observed diffuse scattering intensities are explained by including the correlation effects among thermal displacements of atoms. The force constants among neighboring atoms in Ag(2)O are obtained from the values of correlation effects and Debye-Waller temperature parameters at 295 K. © 2012, Elsevier Ltd.
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    Pressure dependence of crystal structure of Cu2O by TOF powder neutron diffraction
    (Elsevier, 2014-09-01) Ishikawa, Y; Sakuma, T; Takahashi, H; Danilkin, SA
    Neutron diffraction measurements were performed on powder Cu2O with different samples that are pressure released after a pressing force of 295 K with iMATERIA (IBARAKI Materials Designed Diffractometer) installed at MLF in J-PARC. Peak widths of Bragg lines increased depending on the pressing force. To clarify the relation between the crystallite size and the microstrain effect, Rietveld refinement analysis on a TOF neutron diffraction pattern of Cu2O was performed by assuming a cubic cuprite type structure (space group Pn-3m). Strain and crystallite size effects were estimated from Lorentzian terms in the Pseudo-Voigt profile function with a pair of Back-to-Back exponential types based on the Stephenes model. It is considered that the increasing peak width according to the dependence of pressing force is mainly derived from strain effects. And this result is consistent with the previous studies of Ag2O where the Williamson–Hall plot method by X-ray diffraction was applied. © 2013, Elsevier B.V.
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    Pressure-induced superconductivity in the iron-based ladder material BaFe2S3
    (Springer Nature, 2015-07-20) Takahashi, H; Sugimoto, A; Nambu, Y; Yamauchi, T; Hirata, Y; Kawakami, T; Avdeev, M; Matsubayashi, K; Du, F; Kawashima, C; Soeda, H; Nakano, S; Uwatoko, Y; Ueda, Y; Sato, TJ; Ohgushi, K
    All the iron-based superconductors identified so far share a square lattice composed of Fe atoms as a common feature, despite having different crystal structures. In copper-based materials, the superconducting phase emerges not only in square-lattice structures but also in ladder structures. Yet iron-based superconductors without a square-lattice motif have not been found, despite being actively sought out. Here, we report the discovery of pressure-induced superconductivity in the iron-based spin-ladder material BaFe2S3, a Mott insulator with striped-type magnetic ordering below ∼120 K. On the application of pressure this compound exhibits a metal–insulator transition at about 11 GPa, followed by the appearance of superconductivity below Tc = 14 K, right after the onset of the metallic phase. Our findings indicate that iron-based ladder compounds represent promising material platforms, in particular for studying the fundamentals of iron-based superconductivity. © 2015, Nature Publishing Group