Nishida, Satoru*; Nishino, Soichiro*; Sekine, Masahiko*; Oka, Yuki*; Harjo, S.; Kawasaki, Takuro; Suzuki, Hiroshi; Morii, Yukio*; Ishii, Yoshinobu*
Materials Transactions, 62(5), p.667 - 674, 2021/05
Yoshii, Kenji; Ikeda, Naoshi*; Shimojo, Yutaka; Ishii, Yoshinobu*
Materials Chemistry and Physics, 190, p.96 - 101, 2017/04
Magnetic and dielectric properties have been studied for LaCrO, PrCrO, and their solid solution LaPrCrO, belonging to a family of ferroelectricorthochromite series CrO (: rare earths). The magnetic measurements confirm that the material shows canted antiferromagnetic ordering at 240-288 K. Neutron diffraction patterns could be fitted with the centrosymmetric , which is different from the non-centrosymmetric structure proposed for the ferroelectric phase of NdCrO. The large dielectric constants are likely due to the hopping of charge carriers as proposed previously for other chromites.
Okubo, Takeru; Ishii, Yasuyuki; Miyake, Yoshinobu*; Kamiya, Tomihiro
AIP Conference Proceedings 1525, p.370 - 374, 2013/04
Igawa, Naoki; Taguchi, Tomitsugu; Hoshikawa, Akinori*; Yamauchi, Hiroki; Birumachi, Atsushi; Ishii, Yoshinobu*
IOP Conference Series; Materials Science and Engineering, 18, p.022021_1 - 022021_4, 2011/05
The neutron scattering length density distributions of Xe deuterohydrate were analyzed by Rietveld and MEM analysis applied to neutron powder diffraction data to clarify the Xe behavior in the temperature range from 10 to 245 K. A spherical positive scattering length density attributed to the Xe atom was observed at the center of the small cage of the hydrate. On the other hand, an ellipsoid shaped scattering length density distribution at the center of the large cage was observed; the major axis of the ellipsoid scattering length density was directed toward the center of a hexagonal facet of the large cage. The distributions of the Xe atom in the both cages were almost the same at any temperature.
Yoshii, Kenji; Hiramitsu, Yusuke*; Okajima, Yuka*; Yoneda, Yasuhiro; Nishihata, Yasuo; Mizuki, Junichiro; Nakamura, Akio; Shimojo, Yutaka; Ishii, Yoshinobu*; Morii, Yukio; et al.
Materials Research Bulletin, 45(11), p.1574 - 1580, 2010/10
Magnetic and dielectric properties of perovskite manganites RSrMnO (R = Gd, Tb and Dy) have been investigated. DC and AC magnetic measurements showed short-range glassy magnetic ordering at Tg about 40 K. Such ordering was observed by neutron diffraction and is ascribable to the size mismatch of R and Sr settled randomly at the same crystallographic site. Dielectric constants for each material were about 1000-10000 between about 50 K and 300 K and showed broad maximums above Tg. Dielectric dispersion showed poor coherency of the motion of polar regions, plausibly because of the size-mismatch effect; both the magnetic and dielectric properties of this system are governed by the randomness at the R/Sr site. The tan and EXAFS data suggest that the dielectric response is rooted in a transfer of the Mn-3d electrons.
Igawa, Naoki; Taguchi, Tomitsugu; Hoshikawa, Akinori*; Fukazawa, Hiroshi; Yamauchi, Hiroki; Utsumi, Wataru; Ishii, Yoshinobu*
Journal of Physics and Chemistry of Solids, 71(6), p.899 - 905, 2010/06
Crystal structures of carbon dioxide deuterohydrate were studied by neutron powder diffraction at temperatures from 10 to 200 K. Maps of scattering length density distribution were obtained using a maximum entropy method, which clarified the motion of CO molecules in the hydrate. In small cages, the carbon atom of the CO molecule is at the center of the cage, and the oxygen atoms of CO revolve freely around the carbon atom. In large cages, the carbon atom also is at the center of the cage, but the oxygen atoms tend to revolve around the carbon atom along the plane parallel to the hexagonal facets of the cage.
Xianglian*; Siagian, S.*; Basar, K.*; Sakuma, Takashi*; Takahashi, Haruyuki*; Igawa, Naoki; Ishii, Yoshinobu*
Solid State Ionics, 180(6-8), p.480 - 482, 2009/05
Correlation effects among thermal vibrations of atoms are very important to realize the thermal properties of materials. We discuss the inter-atomic distance and temperature dependence of the correlation effects in ionic crystal, AgBr, CuBr, CuI and CuCl, by neutron diffraction method. From the Rietveld analysis of those diffraction data the lattice constants and Deby-Waller parameters were determined. The diffuse scattering of diffraction data was analyzed with the correlation effect, . It is found that the is 0.6-0.75 for the inter-atomic distance around 2.5 and 0.4-0.5 for 4 for all ionic crystals. The value of decreases with the decrease of temperature.
Basar, K.*; Xianglian*; Siagian, S.*; Ohara, Kota*; Sakuma, Takashi*; Takahashi, Haruyuki*; Abe, Osami*; Igawa, Naoki; Ishii, Yoshinobu*
Indonesian Journal of Physics, 20(1), p.9 - 11, 2009/01
Nanosized LiMnO has been successfully prepared by solid state reaction of LiOH and MnO. Neutron scattering experiments at room temperature and conductivity measurement have been performed on the samples. Anneal temperature effect on the crystallite size and electric conductivity of LiMnO is analyzed. The average crystallite size is obtained from the full width at half maximum (FWHM) of Bragg lines using Scherrer equation. The average crystallite size increases with the increase of anneal temperature. Activation energy and conductivity prefactor increase with anneal temperature.
Yamauchi, Hiroki; Ishii, Yoshinobu*; Igawa, Naoki; Fukazawa, Hiroshi; Utsumi, Wataru
JAEA-Research 2008-077, 28 Pages, 2008/10
The neutron powder diffractometer, HRPD, can provide high-resolution data that meet the many users' needs until now. On the other hand, the demand of high-efficiency is growing in the recent years. In order to improve the source intensity and measurement efficiency, the authors tried to develop asymmetric reflection-type Ge monochromators. The mosaic crystals (20 in the horizontal direction) were cut at an angle of 40 relative to the Ge,3,3,1 reflecting planes. The diffraction results of standard Si samples reveal that peak intensities by the asymmetric type are improved 1.2 times larger than those by the existing symmetric type, but integrated intensities are almost comparable each other. For mosaic crystals, asymmetric reflections in compression geometry intensify the current density, but reflectivity is always less than that in symmetric reflections, and thus the suppression of the reflectivity just cancels out the enhancement of the current density.
Nagasaki, Takanori*; Ito, Tsuyoshi*; Yoshino, Masahito*; Iwasaki, Kota*; Shiotani, Shinya*; Fukazawa, Hiroshi; Igawa, Naoki; Ishii, Yoshinobu*
Journal of Nuclear Science and Technology, 45(Suppl.6), p.122 - 127, 2008/09
The neutron powder diffraction measurement was carried out at 10 K on the proton-conducting oxide BaZrInO with and without dissolved DO. Obtained diffraction data were analyzed by the Rietveld method and the maximum entropy method. It was found that deuterium atoms were located close the 12 site of the cubic perovskite structure with the space group -.
Xianglian*; Basar, K.*; Honda, Hiroyuki*; Siagian, S.*; Ohara, Kota*; Sakuma, Takashi*; Takahashi, Haruyuki*; Igawa, Naoki; Ishii, Yoshinobu*
Solid State Ionics, 179(21-26), p.776 - 779, 2008/09
Diffuse X-ray and neutron scattering from powder PbF are measured at 15 and 294K. Those oscillatory profile of diffuse scattering is explained by including the correlation effects among thermal displacements of atoms. The contribution of correlated thermal vibration of Pb-Pb atoms located at far-off distance to the oscillatory profile of diffuse scattering intensities is first confirmed.
Shimoyama, Tomotaka*; Tojo, Takeo*; Kawaji, Hitoshi*; Atake, Toru*; Igawa, Naoki; Ishii, Yoshinobu*
Solid State Ionics, 179(7-8), p.231 - 235, 2008/04
The neutron diffraction study was carried out to determine the location of proton conducting mixed perovskite-type oxide BaCaNbO at 300K. The obtained data have been analyzed by the Rietveld method and the maximum entropy method. The crystal structure of the sample is refined on the basis of the cubic structure with the space group -3. We found that oxide ion locates at 24 site and deuterium 96 site, respectively. The distance between oxide ion and deuterium sites is about 0.72, which is shorter than the normal distance of OD group. The oxygen in OD group is shifted from 24 site slightly toward the opposite side of deuterium and the deuterium is shifted to the Ca/Nb mixed site.
Hiramitsu, Yusuke*; Yoshii, Kenji; Yoneda, Yasuhiro; Mizuki, Junichiro; Nakamura, Akio; Shimojo, Yutaka; Ishii, Yoshinobu*; Morii, Yukio; Ikeda, Naoshi*
Japanese Journal of Applied Physics, Part 1, 46(10B), p.7171 - 7174, 2007/10
Magnetic and dielectric properties of a perivskite manganite TbCaMnO were investigated. Magnetic measurements showed three characteristic temperatures, originating from charge ordering (300 K), antiferromagnetic ordering (120 K) and a transition to a glassy state (50 K). The coexistence of the charge and antiferromagnetic ordering was consistent with the result of powder neutron diffraction. AC dielectric measurements showed large dielectric constants of about 5000 at around room temperature. A temperature dependence of the dielectric constant changed just below the charge-ordering temperature. From the analysis of tan;, the activation energy for a domain-boundary motion was calculated to be about 0.09 eV. These results strongly suggest that the dielectric properties of this material are governed by the ordering and transfer of the Mn-3d charges.
Igawa, Naoki; Taguchi, Tomitsugu; Yamada, Reiji; Ishii, Yoshinobu; Jitsukawa, Shiro
Journal of Nuclear Materials, 367-370(1), p.725 - 729, 2007/08
no abstracts in English
Ito, Tsuyoshi*; Nagasaki, Takanori*; Iwasaki, Kota*; Yoshino, Masahito*; Matsui, Tsuneo*; Fukazawa, Hiroshi; Igawa, Naoki; Ishii, Yoshinobu
Solid State Ionics, 178(7-10), p.607 - 613, 2007/04
no abstracts in English
Yunus, S. M.*; Yamauchi, Hiroki; Zakaria, A. K. M.*; Igawa, Naoki; Hoshikawa, Akinori; Ishii, Yoshinobu
Journal of Magnetism and Magnetic Materials, 310(2, Part3), p.2722 - 2724, 2007/03
Temperature dependent neutron diffraction studies were done on the spinel oxide system MgCoCrFeO (, 0.25, 0.50, 0.75 and 1.0). Neutron diffraction data recorded in the temperature range 10,,810 K were analyzed in the Rietveld method. Ordered sublattice magnetic moments of the five compositions of the spinel series at various temperatures were deduced from the analysis. A decreasing ordered moment with increasing substitution () was found indicating a gradual weakening of ferrimagnetic order. Huge diffuse signals around the 1,1,1 Bragg diffraction peak were found in the neutron patterns of the composition ,=,1.0 below the Curie temperature manifesting a build-up of short-range magnetic spin clusters. The observed features suggest a canted ferrimagnetic structure in the composition range ,,0.75 and a semi-spin glass like transition at ,=,1.0.
Yoshii, Kenji; Mizumaki, Masaichiro*; Kato, Kazuo*; Uruga, Tomoya*; Abe, Hideki*; Nakamura, Akio; Shimojo, Yutaka; Ishii, Yoshinobu; Morii, Yukio
Journal of Solid State Chemistry, 180(1), p.377 - 381, 2007/01
no abstracts in English
Ito, Tsuyoshi*; Nagasaki, Takanori*; Iwasaki, Kota*; Yoshino, Masahito*; Matsui, Tsuneo*; Igawa, Naoki; Ishii, Yoshinobu
Solid State Ionics, 178(1-2), p.13 - 17, 2007/01
no abstracts in English
Inoue, Kazuko*; Yamaguchi, Yasuo*; Ishii, Yoshinobu; Yamauchi, Hiroki; Shishido, Toetsu*
Materials Science Forum, 539-543, p.3267 - 3272, 2007/00
Magnetic field effect on a Heusler-type NiMnGa off-stoichiometric alloy having a martensitic transformation temperature around room temperature which is coincident with a Curie temperature has been investigated. The precess of martensitic transforation of a single crystal was investigated by neutron diffraction under the magnetic field up to 8 Tesla. It was found that the magnetic field, which is applied at a temperature near the transformation temperature, causes the martensitic transformation. The process of the transformation caused by the increase of magnetic field is quite similar to the process caused by the decrease of temperature.
Fukazawa, Hiroshi; Hoshikawa, Akinori; Ishii, Yoshinobu; Chakoumakos, B. C.*; Fernandez-Baca, J. A.*
Astrophysical Journal, 652(1, Part2), p.L57 - L60, 2006/11
Whether ferroelectric ice, named ice XI, exists in a stable low-temperature phase attracts much interest. This question arose as a condensed-matter issue, and became of interest in astronomy (e.g., does ice XI exist on Pluto?) because astronomical observations identified the existence of crystalline ice in our solar system. From neutron diffraction experiments, we found the temperature conditions for the transformation of the largest fraction of ice into ice XI using the lowest level of impurity dopant. The finding of bulk crystal of ordered structure firmly supports that ice XI is stable. This suggests the existence of naturally occurring ice XI at a narrow temperature range (57-66 K) in our solar system.