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Journal Articles

Microscopic analyses of complexes formed in adsorbent for Mo and Zr separation chromatography

Abe, Ryoji*; Nagoshi, Kohei*; Arai, Tsuyoshi*; Watanabe, So; Sano, Yuichi; Matsuura, Haruaki*; Takagi, Hideaki*; Shimizu, Nobutaka*; Koka, Masashi*; Sato, Takahiro*

Nuclear Instruments and Methods in Physics Research B, 404, p.173 - 178, 2017/08

https://doi.org/10.1016/j.nimb.2017.02.082

Times Cited Count：5 Percentile：44.07(Instruments & Instrumentation)

Journal Articles

New AESJ thermal-hydraulics roadmap for LWR safety improvement and development after Fukushima accident

Nakamura, Hideo; Arai, Kenji*; Oikawa, Hirohide*; Fujii, Tadashi*; Umezawa, Shigemitsu*; Abe, Yutaka*; Sugimoto, Jun*; Koshizuka, Seiichi*; Yamaguchi, Akira*

Proceedings of 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-16) (USB Flash Drive), p.5353 - 5366, 2015/08

Journal Articles

Inelastic neutron scattering on iron-based superconductor BaFe(As,P)

Ishikado, Motoyuki; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Wakimoto, Shuichi; Iyo, Akira*; Eisaki, Hiroshi*; Arai, Masatoshi; Shamoto, Shinichi

Physica C, 471(21-22), p.643 - 646, 2011/11

https://doi.org/10.1016/j.physc.2011.05.016

Times Cited Count：4 Percentile：20.79(Physics, Applied)

Superconducting gap symmetry of 1111 system, which has the highest in iron-based superconductors, is considered to be full gap $s_{pm}$ wave based on magnetic penetration depth and neutron scattering measurements. On the other hand, a line node gap symmetry is proposed in BaFe(As,P) based on magnetic penetration depth and thermal conductivity measurements despite comparatively its high- (=30 K). Inelastic neutron scattering of BaFe(As,P) may exhibit different magnetic excitations in the -position or -dependence of a resonant peak from that of La1111 system. In this study, we performed inelastic neutron scattering measurement on 36g polycrystalline powder sample of optimally-doped BaFe(As,P) using Fermi chopper spectrometer 4SEASONS in J-PARC. We will discuss about the possible superconducting gap symmetry based on our inelastic neutron scattering results.

Journal Articles

Neutron scattering of iron-based superconductors

Shamoto, Shinichi; Wakimoto, Shuichi; Kodama, Katsuaki; Ishikado, Motoyuki; Christianson, A. D.*; Lumsden, M. D.*; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Arai, Masatoshi; et al.

Physica C, 471(21-22), p.639 - 642, 2011/11

https://doi.org/10.1016/j.physc.2011.05.015

Times Cited Count：0 Percentile：0(Physics, Applied)

We have studied low-energy spin excitations on polycrystalline LaFeAsO $_{1-x}$ F $_{x}$ samples by inelastic neutron scattering. The dynamical spin susceptibility ''() of the superconducting samples is found to be comparable to that of the magnetically ordered parent sample. On the other hand, ''() almost vanishes at x=0.158, where the superconducting transition temperature T $_{c}$ is suppressed to 7 K. This suggests that the low energy spin excitations are closely connected with high-T $_{c}$ superconductivity. The disappearance of the spin excitations at low energy would correspond to the disappearance of the hole Fermi surface as the electron concentration increases with doping, as observed in ARPES measurements of BaFe $_{2-x}$ Co $_{x}$ As $_{2}$ at x=0.15. The relationship between the spin excitation and the Fermi surface will be discussed in comparison with other iron-based superconductors.

Journal Articles

$s_{pm}$ -like spin resonance in the iron-based nodal superconductor BaFe(As $_{0.65}$ P $_{0.35}$ ) observed using inelastic neutron scattering

Ishikado, Motoyuki; Nagai, Yuki; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Wakimoto, Shuichi; Nakamura, Hiroki; Machida, Masahiko; Suzuki, Katsuhiro*; et al.

Physical Review B, 84(14), p.144517_1 - 144517_5, 2011/10

https://doi.org/10.1103/PhysRevB.84.144517

Times Cited Count：27 Percentile：70.58(Materials Science, Multidisciplinary)

We performed inelastic neutron scattering on a powder sample of iron-based superconductor BaFe(As $_{0.65}$ P $_{0.35}$ ) with = 30 K. Although this system is expected to have line nodes in its superconducting order parameter, we have observed spin resonance at the same scattering vector as that appeared in the $s_{pm}$ -wave iron-based superconductors without line nodes. Moreover, the resonance enhancement, which can be a measure of the area of sign reversal between the hole and electron Fermi surfaces (FSs), is comparable to those without line nodes. These facts indicate that the sign reversal between the FSs is still dominant in this system, and the line nodes should create only limited area of sign-reversal on a single FS. Hence the system can hold higher Tc than the other iron-based superconductors with nodal symmetry, such as LaFePO $_{1-y}$ and KFeAs ( 10 K).

Journal Articles

Soft and isotropic phonons in PrFeAsO $_{1-y}$

Fukuda, Tatsuo; Baron, A. Q. R.*; Nakamura, Hiroki; Shamoto, Shinichi; Ishikado, Motoyuki; Machida, Masahiko; Uchiyama, Hiroshi*; Iyo, Akira*; Kito, Hijiri*; Mizuki, Junichiro; et al.

Physical Review B, 84(6), p.064504_1 - 064504_13, 2011/08

https://doi.org/10.1103/PhysRevB.84.064504

Times Cited Count：9 Percentile：39.24(Materials Science, Multidisciplinary)

Journal Articles

Phonon spectra of PrFeAsO $_{1-y}$ via inelastic X-ray scattering

Fukuda, Tatsuo; Baron, A. Q. R.*; Nakamura, Hiroki; Shamoto, Shinichi; Ishikado, Motoyuki; Machida, Masahiko; Uchiyama, Hiroshi*; Iyo, Akira*; Kito, Hijiri*; Mizuki, Junichiro; et al.

Journal of the Physical Society of Japan, 80(Suppl.B), p.SB015_1 - SB015_4, 2011/01

https://doi.org/10.1143/JPSJS.80SB.SB015

Times Cited Count：1 Percentile：11.3(Physics, Multidisciplinary)

We have investigated phonons of PrFeAsO $_{1-y}$ using high-resolution inelastic X-ray scattering and calculations. Extensive measurements show that there are some changes in phonon spectra with temperature and/or doping. However, we compare our data with several calculations and find that the experimentally observed changes are much smaller than differences between the experiment. data and the calculations. Agreement is improved if magnetism is included in the calculations. However, still in disagreement even in the parent sample below T. We consider several modifications of the calculations. The best agreement is obtained from modifying the nonmagnetic calculation. by softening only the in-plane nearest-neighbor Fe-As force constant. Fluctuating magnetism may be a partial explanation for the failure of the calculations, but seems incomplete in the face of the similarity of the measured phonon response in all the systems investigated including those known to have static magnetism.

Journal Articles

Inelastic neutron scattering study of the resonance mode in the optimally doped pnictide superconductor LaFeAsO $_{0.92}$ F $_{0.08}$

Shamoto, Shinichi; Ishikado, Motoyuki; Christianson, A. D.*; Lumsden, M. D.*; Wakimoto, Shuichi; Kodama, Katsuaki; Iyo, Akira*; Arai, Masatoshi

Physical Review B, 82(17), p.172508_1 - 172508_4, 2010/11

https://doi.org/10.1103/PhysRevB.82.172508

Times Cited Count：42 Percentile：81.29(Materials Science, Multidisciplinary)

An optimally doped iron-based superconductor LaFeAsO $_{0.92}$ F $_{0.08}$ with T $_{c}$ =29 K has been studied by inelastic powder neutron scattering. The magnetic excitation at Q = 1.15 $^{-1}$ is enhanced below T $_{c}$ , leading to a peak at E $_{res}$ =13 meV as the resonance mode.

Journal Articles

Degradation of superconductivity and spin fluctuations by electron overdoping in LaFeAsO $_{1-x}$ F $_{x}$

Wakimoto, Shuichi; Kodama, Katsuaki; Ishikado, Motoyuki; Matsuda, Masaaki; Kajimoto, Ryoichi; Arai, Masatoshi; Kakurai, Kazuhisa; Esaka, Fumitaka; Iyo, Akira*; Kito, Hijiri*; et al.

Journal of the Physical Society of Japan, 79(7), p.074715_1 - 074715_4, 2010/07

https://doi.org/10.1143/JPSJ.79.074715

Times Cited Count：50 Percentile：86.18(Physics, Multidisciplinary)

Journal Articles

Two-dimensional spin density wave state in LaFeAsO

Ishikado, Motoyuki; Kajimoto, Ryoichi; Shamoto, Shinichi; Arai, Masatoshi; Iyo, Akira*; Miyazawa, Kiichi*; Shirage, P. M.*; Kito, Hijiri*; Eisaki, Hiroshi*; Kim, S.-W.*; et al.

Journal of the Physical Society of Japan, 78(4), p.043705_1 - 043705_4, 2009/04

https://doi.org/10.1143/JPSJ.78.043705

Times Cited Count：34 Percentile：80.47(Physics, Multidisciplinary)

Journal Articles

Lattice dynamics of LaFeAsO $_{1-x}$ F and PrFeAsO $_{1-y}$ via inelastic X-ray scattering and first-principles calculation

Fukuda, Tatsuo; Baron, A. Q. R.*; Shamoto, Shinichi; Ishikado, Motoyuki; Nakamura, Hiroki; Machida, Masahiko; Uchiyama, Hiroshi*; Tsutsui, Satoshi*; Iyo, Akira*; Kito, Hijiri*; et al.

Journal of the Physical Society of Japan, 77(10), p.103715_1 - 103715_4, 2008/10

https://doi.org/10.1143/JPSJ.77.103715

Times Cited Count：42 Percentile：83.16(Physics, Multidisciplinary)

The lattice dynamics of LaFeAsO $_{1-x}$ F (=0, 0.1) and PrFeAsO $_{1-y}$ (0.1) are investigated using inelastic X-ray scattering. Measurements of powder samples provide an approximation to the phonon DOS, while dispersion is measured from a single crystal of PrFeAsO $_{1-y}$ . A model that agrees reasonably well with all of the data at room temperature is built from results of ab-initio calculations by reducing the strength of the Fe-As bond by 30%.

Journal Articles

Rheo-SANS study on gelation of poly(vinyl alcohol)

Takahashi, Nobuaki; Kanaya, Toshiji*; Nishida, Koji*; Takahashi, Yoshiaki*; Arai, Masatoshi

Physica B; Condensed Matter, 385-386(1), p.810 - 813, 2006/11

https://doi.org/10.1016/j.physb.2006.06.096

Times Cited Count：6 Percentile：31.16(Physics, Condensed Matter)

We have studied shear flow effects on physical gelation processes of poly(vinyl alcohol) solutions in a mixture of deuterated dimethyl sulfoxide and heavy water using time-resolved 2D-SANS technique with a rheological setup. Steady shear flow was applied on the sample solution after quenching from 100 $^{circ}$ C to 25 $^{circ}$ C, and the isothermal measurements were performed. The observed two-dimensional scattering patterns under the shear flow were isotropic while the growth rate of the scattering intensity was affected. It has been revealed in a previous report that the gelation of the solution was caused through crystallization between polymer chains to form the network. Hence, focusing on the scattering intensity from the crystallites, we have evaluated the crystallization rate. It was found that the crystallization rate was accelerated in a low shear rate region (shear rate is smaller than 5 sec $^{-1}$ ) and decreased with increasing the shear rate in a high rate region (bigger than 5 sec $^{-1}$ ) after a maximum at 5 sec $^{-1}$ . The results suggest that the local orientation of flexible polymer chains due to the shear flow assist crystal nucleation in the low shear rate region while the once-formed crystallites are destroyed by the shear in the high shear rate region.

Journal Articles

Chemical abundances in the secondary star of the black hole binary V4641 Sagittarii (SAX J1819.3-2525)

Sadakane, Kozo*; Arai, Akira*; Aoki, Wako*; Arimoto, Nobuo*; Hidai, Masahide*; Onishi, Takashi*; Tajitsu, Akito*; Beers, T. C.*; Iwamoto, Nobuyuki; Tominaga, Nozomu*; et al.

Publications of the Astronomical Society of Japan, 58(3), p.595 - 604, 2006/06

https://doi.org/10.1093/pasj/58.3.595

Times Cited Count：11 Percentile：31.85(Astronomy & Astrophysics)

We report detailed spectroscopic studies performed for the secondary star in the black hole binary (micro-quasar) V4641 Sgr in order to examine its surface chemical composition and to see if its surface shows any signature of pollution by ejecta from a supernova explosion. We obtain abundances of 10 elements and find definite over-abundances of N (by 0.8 dex or more) and Na (by 0.8 dex) in V4641 Sgr. From line-by-line comparisons of eight other elements (C, O, Mg, Al, Si, Ti, Cr, Fe) between V4641 Sgr and the two normal late B-type stars, which have been reported to have solar abundances. An evolutionary model of a massive close binary system has been constructed to explain the abundances observed in V4641 Sgr. The model suggests that the BH forming supernova in this system was a dark one.

Journal Articles