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Hashimoto, Shunsuke*; Yamaguchi, Satoshi*; Harada, Masashi*; Nakajima, Kenji; Kikuchi, Tatsuya*; Oishi, Kazuki*
Journal of Colloid and Interface Science, 638, p.475 - 486, 2023/05
Times Cited Count：2 Percentile：66.51(Chemistry, Physical)Recently, it has been reported that anomalous improvement in the thermal conductivity of nanofluid composed of base liquids and dispersed solid nanoparticles, compared to the theoretically predicted value calculated from the particle fraction. Generally, the thermal conductivity values of gases and liquids are dominated by the mean free path of the molecules during translational motion. Herein, we present solid evidence showing the possible contribution of the vibrational behavior of liquid molecules around nanoparticles to increasing these thermal conductivities.
H
OFujihara, Masayoshi; Hagihara, Masato; Morita, Katsuhiro*; Murai, Naoki; Koda, Akihiro*; Okabe, Hirotaka*; Mitsuda, Setsuo*
Physical Review B, 107(5), p.054435_1 - 054435_8, 2023/02
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)The 
= 1/2 Heisenberg linear chain antiferromagnet is the simplest spin model; nevertheless it serves as a platform for various quantum many-body phenomena. Here, we report the magnetic behavior of a quasi-one-dimensional antiferromagnet KCuPOHO. A long-range commensurate antiferromagnetic order with ordered moment 0.31(1) 
per spin occurs at 
= 11.7(1) K. Above , the inelastic neutron excitation is characterized by a two spinon continuum. The intrachain interaction 
and interchain interaction 
are estimated to be 172 K and 4.25(4) K, respectively; thus the ratio of the / = 0.0247(3). At lower energies, below , a spin gap is observed in the dispersive excitations. These results are consistent with characteristics observed in weakly interacting = 1/2 Heisenberg chain system.
Nakajima, Kenji; Kikuchi, Tatsuya*; Kawamura, Seiko; Kambara, Wataru*
EPJ Web of Conferences, 272, p.02012_1 - 02012_8, 2022/11
We will present some of attempts on AMATEAS, a cold-neutron chopper spectrometer at a pulsed source, to increase time-windows at a single-measurement condition. One of ways is that, by allowing interveined trajectories on the time-of-flight diagram, the usable width selectable for 
is can be increased. Based on our experiences, the conditions of pulse repetition rate multiplication based polychromatic 
measurements on chopper spectrometers at pulsed sources will be discussed. Optimization of wide-band polychromatic measurements and a generalized formulated condition will be proposed. Application of our idea to existing spectrometers and to the criteria design of an optimized chopper spectrometer will be also discussed with suggesting further possibility to improve efficiency by modifying the pulse shaping chopper.
and TiH
up to 21 GPa by incoherent inelastic neutron scatteringHattori, Takanori; Nakamura, Mitsutaka; Iida, Kazuki*; Machida, Akihiko*; Sano, Asami; Machida, Shinichi*; Arima, Hiroshi*; Oshita, Hidetoshi*; Honda, Takashi*; Ikeda, Kazutaka*; et al.
Physical Review B, 106(13), p.134309_1 - 134309_9, 2022/10
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)Hydrogen vibration excitations of fluorite-type ZrH and TiH were investigated up to 21 GPa and 4 GPa, respectively, by incoherent inelastic neutron scattering experiments. The first excitation energies increased with pressure, as described by the equations 
(meV) = 141.4(2) + 1.02(2)
(GPa) and (meV) = 149.4(1) + 1.21(8)(GPa) for ZrH and TiH, respectively. Coupling with pressure dependence of lattice parameters, the relations between metal-hydrogen distance (
) and are found to be well described by the equations (meV) = 1.62(9)
10
(
(meV) = 1.47(21) 10 
(AA), respectively. The slopes of these curves are much steep compared to the previously reported trend in various fluorite-type metal hydrides at ambient pressure. The hydrogen wave function spreading showed that the local potential field for a hydrogen atom shrinks more intensively than the tetrahedral site. These behavior is likely caused by the rigid metal ion core and the resulting confinement of the hydrogen atom in the narrower potential field at high pressures.
Al
and Nd
Pd
Ge
Metoki, Naoto; Shibata, Kaoru; Matsuura, Masato*; Kitazawa, Hideaki*; Suzuki, Hiroyuki*; Yamauchi, Hiroki; Hagihara, Masato; Frontzek, M. D.*; Matsuda, Masaaki*
Journal of the Physical Society of Japan, 91(5), p.054710_1 - 054710_6, 2022/05
Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)Hyperfine splitting of Nd nuclei in NdPdAl has been studied by means of high-resolution neutron spectroscopy. We observed inelastic peaks at 
eV coming from the hyperfine splitting in the magnetically ordered phase due to the hyperfine interactions between Nd nuclei (
=7/2) and the 4
electrons with 
ground state composed of mainly 
. At very low temperatures, nuclear spin of Nd is polarized with increasing occupation probability of low energy levels and contributes to the enhancement of the antiferromagnetic Bragg intensities: the elastic non-spin-flip channel is dominant. As an application of this phenomenon, we determined the Nd moment and hyperfine splitting from the temperature dependence of an antiferromagnetic Bragg intensities for NdPdGe.
Yang, J.*; Ren, W.*; Zhao, X.*; Kikuchi, Tatsuya*; Miao, P.*; Nakajima, Kenji; Li, B.*; Zhang, Z.*
Journal of Materials Science & Technology, 99, p.55 - 60, 2022/02
Times Cited Count：5 Percentile：41.35(Materials Science, Multidisciplinary)High-entropy alloys are characteristic of extensive atomic occupational disorder on high-symmetric lattices, differing from traditional alloys. Here, we investigate magnetic and thermal transport properties of the prototype face-centered-cubic high-entropy alloy CrMnFeCoNi by combining physical properties measurements and neutron scattering. Direct-current (dc) and alternating-current (ac) magnetizations measurements indicate a mictomagnetic behavior with coexisting antiferromagnetic and ferromagnetic interactions in the entire temperature region and three anomalies are found at about 80, 50, and 20 K, which are related to the paramagnetic to antiferromagnetic transition, the antiferromagnetic to ferromagnetic transition, and the spin freezing, respectively. The electrical and thermal conductivities are significantly reduced compared to Ni and the temperature dependence of lattice thermal conductivity exhibits a glass-like plateau. Inelastic neutron scattering measurements suggest weak anharmonicity so that the thermal transport is expected to be dominated by the defect scattering.
anisotropic triangular antiferromagnet Ca
ReO
ClNawa, Kazuhiro*; Hirai, Daigoro*; Kofu, Maiko; Nakajima, Kenji; Murasaki, Ryo*; Kogane, Satoshi*; Kimata, Motoi*; Nojiri, Hiroyuki*; Hiroi, Zenji*; Sato, Taku*
Physical Review Research (Internet), 2(4), p.043121_1 - 043121_11, 2020/12
The spin excitations of the = anisotropic triangular antiferromagnet CaReOCl were investigated by inelastic neutron-scattering experiments. The spin excitation spectrum exhibits sharp dispersive modes in addition to a spinonlike continuum. The consistency with the simulated spectrum based on the random-phase approximation is better for CaReOCl than for CsCuCl, indicating that the spin system in the former remains closer to a Tomonaga-Luttinger liquidlike disordered state.
Kojima, Seiji*; Novikov, V. N.*; Kofu, Maiko; Yamamuro, Osamu*
Physica Status Solidi (B), 257(11), p.200073_1 - 200073_6, 2020/11
Times Cited Count：3 Percentile：19.68(Physics, Condensed Matter)-electron states of NpPdAl and the isostructural family; Heavy fermion superconductivity accompanied by valence crossoverMetoki, Naoto
Kotai Butsuri, 55(7), p.285 - 296, 2020/07
Electron states are the main theme of "solid-state physics", which is essential for microscopic understanding of multipoles and superconductivity, etc. Rare earths (4) and actinides (5) provide variety of interesting states realized with competing interactions between the increasing number of electrons. Since crystal field splitting of many-body electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the electron states of heavy electron compounds NpPd
Al and actinide and rare earth based iso-structural family.
Fujihara, Masayoshi*; Morita, Katsuhiro*; Mole, R.*; Mitsuda, Setsuo*; Toyama, Takami*; Yano, Shinichiro*; Yu, D.*; Sota, Shigetoshi*; Kuwai, Tomohiko*; Koda, Akihiro*; et al.
Nature Communications (Internet), 11, p.3429_1 - 3429_7, 2020/07
Times Cited Count：37 Percentile：90.63(Multidisciplinary Sciences)OAllenspach, S.*; Biffin, A.*; Stuhr, U.*; Tucker, G. S.*; Kawamura, Seiko; Kofu, Maiko; Voneshen, D. J.*; Boehm, M.*; Normand, B.*; Laflorencie, N.*; et al.
Physical Review Letters, 124(17), p.177205_1 - 177205_7, 2020/05
Times Cited Count：10 Percentile：65.11(Physics, Multidisciplinary)Nakayama, Shinsuke; Iwamoto, Osamu; Watanabe, Yukinobu*
Physical Review C, 100(4), p.044603_1 - 044603_8, 2019/10
Times Cited Count：7 Percentile：59.68(Physics, Nuclear)The weakly-bound nature of the deuteron brings the complexity of deuteron-induced reactions compared to nucleon-induced ones, and is expected to affect various physical quantities observed in deuteron-induced reactions. Aiming to deep understanding and accurate prediction for the emission of light composite particle (LCP) in deuteron-induced reactions, we revise the computational system dedicated to deuteron-induced reactions, called DEURACS. The model by Iwamoto and Harada describing pre-equilibrium cluster emission which was successfully applied to LCP emission innucleon-induced reactions is integrated into the framework of DEURACS, in which the breakup processes of incident deuteron are explicitly taken into account. The phenomenological model by Kalbach is also adopted to estimate the contribution from the direct pickup process. Using the revised DEURACS, we analyze the 
, 
, and 
reactions in the target mass range 
. Regardless of the targets, the calculation results successfully reproduced the experimental data for each reaction, simultaneously. These results demonstrates that the LCP emission from the pre-equilibrium and compound nucleus processes in deuteron-induced reactions,which occupies a large part of the total LCP emission,can be described by the same theoretical models as used in nucleon-induced reactions when the breakup processes of incident deuteron are properly considered.
Kojima, Seiji*; Novikov, V. N.*; Kofu, Maiko; Yamamuro, Osamu*
Journal of Non-Crystalline Solids, 518, p.18 - 23, 2019/08
Times Cited Count：6 Percentile：29.81(Materials Science, Ceramics)
Ti
O
Kadowaki, Hiroaki*; Wakita, Mika*; F
k, B.*; Ollivier, J.*; Kawamura, Seiko; Nakajima, Kenji; Takatsu, Hiroshi*; Tamai, Mototake*
Journal of the Physical Society of Japan, 87(6), p.064704_1 - 064704_6, 2018/06
Times Cited Count：9 Percentile：57.38(Physics, Multidisciplinary)The ground states of the frustrated pyrochlore oxide TbTiO have been studied by inelastic neutron scattering experiments. Three single-crystal samples are investigated; one shows no phase transition (
), being a putative quantum spin-liquid (QSL), and the other two (
) show electric quadrupole ordering (QO) below 
K. The QSL sample shows continuum excitation spectra with an energy scale 0.1 meV as well as energy-resolution-limited (nominally) elastic scattering. As 
is increased, pseudospin wave of the QO state emerges from this continuum excitation, which agrees with that of powder samples and consequently verifies good control for the present single crystal samples.
Se
Lee, C. H.*; Nishida, Atsuhiro*; Hasegawa, Takumi*; Nishiate, Hirotaka*; Kunioka, Haruno*; Kawamura, Seiko; Nakamura, Mitsutaka; Nakajima, Kenji; Mizuguchi, Yoshikazu*
Applied Physics Letters, 112(2), p.023903_1 - 023903_4, 2018/01
Times Cited Count：28 Percentile：77.9(Physics, Applied)Low energy phonons in LaOBiSSe are studied using inelastic neutron scattering. Dispersionless flat phonon branches that are mainly associated with a large vibration of Bi atoms are observed at a relatively low energy of = 6 - 6.7 meV. The phonon energy softens upon Se doping owing to its heavier atomic mass than S atom and the expansion of lattice constant. Simultaneously, the lattice thermal conductivity lowered upon Se doping as the same manner of the phonon softening. These suggest that despite the lack of an oversized cage in LaOBiSSe, rattling motions of Bi atoms can scatter phonon like rattling in cage compounds, contributing to enhance the thermoelectric property.
VAl probed by soft X-ray spectroscopiesNagai, Kodai*; Fujiwara, Hidenori*; Aratani, Hidekazu*; Fujioka, Shuhei*; Yomosa, Hiroshi*; Nakatani, Yasuhiro*; Kiss, Takayuki*; Sekiyama, Akira*; Kuroda, Fumiaki*; Fujii, Hitoshi*; et al.
Physical Review B, 97(3), p.035143_1 - 035143_8, 2018/01
Times Cited Count：21 Percentile：70.17(Materials Science, Multidisciplinary)We have studied the electronic structure of ferrimagnetic MnVAl single crystals by means of soft X-ray absorption spectroscopy (XAS), X-ray absorption magnetic circular dichroism (XMCD), and resonant soft X-ray inelastic scattering (RIXS). We have successfully observed the XMCD signals for all the constituent elements. The Mn L
XAS and XMCD spectra are reproduced by spectral simulations based on density-functional theory, indicating the itinerant character of the Mn 3
states. On the other hand, the V 3 electrons are rather localized since the ionic model can qualitatively explain the V L XAS and XMCD spectra. This picture is consistent with local 
excitations revealed by the V L RIXS.
Kofu, Maiko; Hashimoto, Naoki*; Akiba, Hiroshi*; Kobayashi, Hirokazu*; Kitagawa, Hiroshi*; Iida, Kazuki*; Nakamura, Mitsutaka; Yamamuro, Osamu*
Physical Review B, 96(5), p.054304_1 - 054304_7, 2017/08
Times Cited Count：15 Percentile：58.3(Materials Science, Multidisciplinary)The vibrational states of hydrogen atoms in bulk and nanocrystalline palladium were examined in a wide energy region 
meV using neutron spectroscopy. In bulk PdH
, the vibrational excitations of H atoms were roughly reproduced by the quantum harmonic oscillator (QHO) model. In PdH
nanocrystals with a diameter of 8 nm, however, additional vibrational excitations were found at energies above 80 meV. The energies and intensities of the additional states were not explained by QHO but reasonably described as vibrations in a highly anharmonic trumpet-like potential. The additional excitations are attributed to the vibrations of H atoms at tetrahedral sites in the subsurface region stabilized by surface effects. This is an experimental work which clearly detects hydrogen vibration 
metal nanoparticles.
isomer in neutron-rich 
WShizuma, Toshiyuki; Hayakawa, Takehito; Mitarai, Shiro*; Morikawa, Tsuneyasu*; Ishii, Tetsuro
Physical Review C, 71(6), p.067301_1 - 067301_4, 2005/06
Times Cited Count：6 Percentile：45.53(Physics, Nuclear)Excited states in neutron-rich W have been populated via deep inelastic collisions of a 630-MeV 
Se beam on a 
W target. Projectile-like fragments were measured by an annular Si detector for reaction channel selection. Delayed 
rays from target residues were detected by means of the so-called recoil shadow technique. A new isomer at 411 keV, based on the 
[615] Nilsson configuration, has been identified with the half-life of 1.56(28) 
s. The decay rates of the isomers are discussed in terms of the 
quantum number by comparison with the systematics from the neighboring nuclei.
Sb
Kuwahara, Keitaro*; Iwasa, Kazuaki*; Kogi, Masafumi*; Kaneko, Koji; Araki, Shingo; Metoki, Naoto; Sugawara, Hitoshi*; Aoki, Yuji*; Sato, Hideyuki*
Journal of the Physical Society of Japan, 73(6), p.1438 - 1441, 2004/06
Times Cited Count：64 Percentile：87.39(Physics, Multidisciplinary)no abstracts in English
Ba populated by deep inelastic collisionsShizuma, Toshiyuki; Gan, Z. G.*; Ogawa, Kengo*; Nakada, Hitoshi*; Oshima, Masumi; Toh, Yosuke; Hayakawa, Takehito; Hatsukawa, Yuichi; Sugawara, Masahiko*; Utsuno, Yutaka; et al.
European Physical Journal A, 20(2), p.207 - 210, 2004/04
Times Cited Count：13 Percentile：71.74(Physics, Nuclear)Excited states in Ba, populated in deep-inelastic collisions by the interaction of 450-MeV Se ions with a 
La target, have been studied by means of in-beam -ray spectroscopy. A new isomer with 
has been identified at an excitation energy of 
MeV. The half-life was determined as 
ns. The extracted 
value is much smaller than those in 
Te and 
Xe. This hindrance is investigated by a shell model calculation.
