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Journal Articles

Development of spin-contrast-variation neutron powder diffractometry for extracting the structure factor of hydrogen atoms

Miura, Daisuke*; Kumada, Takayuki; Sekine, Yurina; Motokawa, Ryuhei; Nakagawa, Hiroshi; Oba, Yojiro; Ohara, Takashi; Takata, Shinichi; Hiroi, Kosuke; Morikawa, Toshiaki*; et al.

Journal of Applied Crystallography, 54(2), p.454 - 460, 2021/04

 Times Cited Count:0 Percentile:0.02(Chemistry, Multidisciplinary)

We developed a spin-contrast-variation neutron powder diffractometry technique that extracts the structure factor of hydrogen atoms, namely, the contribution of hydrogen atoms to a crystal structure factor. Crystals of L-glutamic acid were dispersed in a dpolystyrene matrix containing 4-methacryloyloxy-2,2,6,6,-tetramethyl-1-piperidinyloxy (TEMPO methacrylate) to polarize their proton spins dynamically. The intensities of the diffraction peaks of the sample changed according to the proton polarization, and the structure factor of the hydrogen atoms was extracted from the proton-polarization dependent intensities. This technique is expected to enable analyses of the structures of hydrogen-containing materials that are difficult to determine with conventional powder diffractometry.

Journal Articles

Development of spin-contrast-variation neutron reflectometry

Kumada, Takayuki; Akutsu, Kazuhiro*; Oishi, Kazuki*; Morikawa, Toshiaki*; Kawamura, Yukihiko*; Sahara, Masae*; Suzuki, Junichi*; Miura, Daisuke*; Torikai, Naoya*

J-PARC 20-02, p.38 - 40, 2021/00

Journal Articles

Contrast variation by dynamic nuclear polarization and time-of-flight small-angle neutron scattering, 1; Application to industrial multi-component nanocomposites

Noda, Yohei*; Koizumi, Satoshi*; Masui, Tomomi*; Mashita, Ryo*; Kishimoto, Hiromichi*; Yamaguchi, Daisuke; Kumada, Takayuki; Takata, Shinichi; Oishi, Kazuki*; Suzuki, Junichi*

Journal of Applied Crystallography, 49(6), p.2036 - 2045, 2016/12

 Times Cited Count:13 Percentile:75.37(Chemistry, Multidisciplinary)

Journal Articles

Radiolysis of boiling water

Yang, S.*; Katsumura, Yosuke*; Yamashita, Shinichi*; Matsuura, Chihiro*; Hiroishi, Daisuke*; Lertnaisat, P.*; Taguchi, Mitsumasa

Radiation Physics and Chemistry, 123, p.14 - 19, 2016/06

 Times Cited Count:2 Percentile:25.63(Chemistry, Physical)

$$gamma$$-radiolysis of boiling water has been investigated. The G-value of H$$_{2}$$ evolution was found to be very sensitive to the purity of water. In high-purity water, both H$$_{2}$$ and O$$_{2}$$ gases were formed in the stoichiometric ratio of 2:1; a negligible amount of H$$_{2}$$O$$_{2}$$ remained in the liquid phase. The G-values of H$$_{2}$$ and O$$_{2}$$ gas evolution depend on the dose rate: lower dose rates produce larger yields. To clarify the importance of the interface between liquid and gas phase for gas evolution, the gas evolution under Ar gas bubbling was measured. A large amount of H$$_{2}$$ was detected, similar to the radiolysis of boiling water. The evolution of gas was enhanced in a 0.5 M NaCl aqueous solution. Deterministic chemical kinetics simulations elucidated the mechanism of radiolysis in boiling water.

Journal Articles

Complementary characterization of radioactivity produced by repetitive laser-driven proton beam using shot-to-shot proton spectral measurement and direct activation measurement

Ogura, Koichi; Shizuma, Toshiyuki; Hayakawa, Takehito; Yogo, Akifumi; Nishiuchi, Mamiko; Orimo, Satoshi; Sagisaka, Akito; Pirozhkov, A. S.; Mori, Michiaki; Kiriyama, Hiromitsu; et al.

Japanese Journal of Applied Physics, 51(4), p.048003_1 - 048003_2, 2012/04

 Times Cited Count:2 Percentile:10.01(Physics, Applied)

A proton beam driven by a repetitive high-intensity-laser is utilized to induce a $$^{7}$$Li(p,n)$$^{7}$$Be nuclear reaction. The total activity of $$^{7}$$Be are evaluated by two different methods. The activity obtained measuring the decay $$gamma$$-rays after 1912 shots at 1 Hz is 1.7$$pm$$0.2 Bq. This is in good agreement with 1.6$$pm$$0.3 Bq evaluated from the proton energy distribution measured using a time-of-flight detector and the nuclear reaction cross-sections. We conclude that the production of activity can be monitored in real time using the time-of-flight-detector placed inside a diverging proton beam coupled with a high-speed signal processing system.

Journal Articles

Multiferroic character and magnetic phase of LuFe$$_{2}$$O$$_{4}$$

Oishi, Daisuke*; Hayakawa, Hironori*; Akahama, Hiroshi*; Ikeda, Naoshi*; Kambe, Takashi*; Matsuo, Yoji*; Kimizuka, Noboru*; Kano, Jun*; Yoshii, Kenji

Ferroelectrics, 415(1), p.51 - 56, 2011/10

 Times Cited Count:5 Percentile:27.56(Materials Science, Multidisciplinary)

The variation of AC dielectric constant in the function of the DC magnetic fields was found in low oxygen vacant LuFe$$_{2}$$O$$_{4}$$ single crystal in which the electric polarization arise from the polar charge ordering. These magneto-electric coupling should be explained by a novel mechanism where the boundary motion of the polar charge ordered domain is affected by the magnetic (spin) domain boundary motion.

Journal Articles

Suppression of time-reversal symmetry breaking superconductivity in Pr(Os$$_{1-x}$$Ru$$_x$$)$$_4$$Sb$$_{12}$$ and Pr$$_{1-y}$$La$$_y$$Os$$_4$$Sb$$_{12}$$

Shu, L.*; Higemoto, Wataru; Aoki, Yuji*; Hillier, A. D.*; Oishi, Kazuki*; Ishida, Kenji*; Kadono, Ryosuke*; Koda, Akihiro*; Bernal, O. O.*; MacLaughlin, D. E.*; et al.

Physical Review B, 83(10), p.100504_1 - 100504_4, 2011/03

 Times Cited Count:28 Percentile:75.21(Materials Science, Multidisciplinary)

Zero-field muon spin relaxation experiments have been carried out in the Pr(Os$$_{1-x}$$Ru$$_x$$)$$_4$$Sb$$_{12}$$ and Pr$$_{1-y}$$La$$_y$$Os$$_4$$Sb$$_{12}$$ alloy systems to investigate broken time-reversal symmetry (TRS) in the superconducting state, signaled by the onset of a spontaneous static local magnetic field B$$_s$$. In both alloy series B$$_s$$ initially decreases linearly with solute concentration. Ru doping is considerably more efficient than La doping, with a 50% faster initial decrease. The data suggest that broken TRS is suppressed for Ru concentration $$xgeq$$0.6 but persists for essentially all La concentrations. Our data support a crystal-field excitonic cooper pairing mechanism for TRS-breaking superconductivity.

Journal Articles

Microscopic study of antiferromagnetic ground state and possible high-field ordered state in CeOs$$_4$$Sb$$_{12}$$ using muon spin rotation and relaxation

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Sato, Kazuhiko*; Aoki, Yuji*; Toda, Shizuka*; Kikuchi, Daisuke*; Sato, Hideyuki*; Baines, C.*

Physical Review B, 82(1), p.014420_1 - 014420_8, 2010/07

 Times Cited Count:7 Percentile:36.48(Materials Science, Multidisciplinary)

An antiferromagnetic (AFM) ground state and a possible high-field ordered state in magnetic fields $$H>1$$ T of a filled-skutterudite compound CeOs$$_4$$Sb$$_{12}$$ were investigated by the muon spin rotation and relaxation method. In a zero applied field, a spontaneous local filed due to the weak AFM ordering was observed below $$sim$$1.6 K. The magnetic volume fraction gradually increases below 1.6 K with decreasing temperature, suggesting that this phase is sensitive to sample quality. The magnitude of the ordered dipole moment in the AFM state was estimated to be in the range from 0.11 to 0.17 $$mu_B$$/Ce at 0.1 K. In a field of 2 T applied along the [001] direction, clear anomalies in the muon Knight shift and line width were observed at $$sim$$ 1.5 K, consistent with the phase transition scenario into the high-field ordered state suggested from specific heat, resistivity, elastic, and NMR anomalies.

Journal Articles

Magneto-electric effect in charge-ordered LuFe$$_{2}$$O$$_{4}$$

Kambe, Takashi*; Komatsu, Takuma*; Michiuchi, Takamasa*; Hayakawa, Hiroki*; Oishi, Daisuke*; Hanasaki, Noriaki*; Yoshii, Kenji; Ikeda, Naoshi*

Journal of Physics; Conference Series, 200, p.012077_1 - 012077_4, 2010/02

 Times Cited Count:4 Percentile:83.16

A magneto-electric effect (ME) was observed in a charge-ordered ferroelectric LuFe$$_{2}$$O$$_{4}$$. The dielectric response in a three-dimensional charge-ordered phase is strongly influenced by magnetic field, especially around the ferri-magnetic ordering temperature. We also show the relation between the oxygen stoichiometry and the ME signal character above the magnetic transition temperature.

Journal Articles

Application of laser-accelerated protons to the demonstration of DNA double-strand breaks in human cancer cells

Yogo, Akifumi; Sato, Katsutoshi; Nishikino, Masaharu; Mori, Michiaki; Teshima, Teruki*; Numasaki, Hodaka*; Murakami, Masao*; Demizu, Yusuke*; Akagi, Takashi*; Nagayama, Shinichi*; et al.

Applied Physics Letters, 94(18), p.181502_1 - 181502_3, 2009/05

 Times Cited Count:95 Percentile:94.5(Physics, Applied)

Journal Articles

Possible low-energy excitations of multipoles in SmRu$$_4$$P$$_{12}$$ probed by muon spin relaxation

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; Sato, Hideyuki*

Physica B; Condensed Matter, 404(5-7), p.761 - 764, 2009/04

 Times Cited Count:1 Percentile:6.65(Physics, Condensed Matter)

We report on detailed longitudinal field (LF) $$mu$$SR studies in SmRu$$_4$$P$$_{12}$$ in order to characterize magnetic fluctuations in a magnetically ordered state below $$T_{rm MI}=16.5$$ K. A magnitude and fluctuation rate of the fluctuating field are derived as functions of temperature from LF dependence of the longitudinal relaxation rate. Possible low-energy excitations of magnetic multipoles are discussed.

Journal Articles

Weak ferromagnetic ordering in the anomalous field-insensitive heavy-fermion state in SmOs$$_4$$Sb$$_{12}$$

Aoki, Yuji*; Higemoto, Wataru; Tsunashima, Yoshino*; Yonezawa, Yuki*; Sato, Koki*; Koda, Akihiro*; Ito, Takashi; Oishi, Kazuki; Heffner, R. H.; Kikuchi, Daisuke*; et al.

Physica B; Condensed Matter, 404(5-7), p.757 - 760, 2009/04

 Times Cited Count:4 Percentile:22.79(Physics, Condensed Matter)

Zero field (ZF) and transverse field (TF) muon spin relaxation and rotation ($$mu$$SR) study has been carried out in filled-skutterudite SmOs$$_4$$Sb$$_{12}$$ in order to investigate the magnetically robust heavy-fermion (HF) state and the weak ferromagnetic anomaly. A large-amplitude oscillating signal appears in the ZF-$$mu$$SR spectra at low temperatures, confirming that the weak ferromagnetic anomaly is an intrinsic bulk property. Analysis reveals that the weak ferromagnetic moment is carried by itinerant heavy quasiparticles.

Journal Articles

Novel features in filled skutterudites containing rare-earth elements with a plural number of 4f-electrons

Sato, Hideyuki*; Aoki, Yuji*; Kikuchi, Daisuke*; Sugawara, Hitoshi*; Higemoto, Wataru; Oishi, Kazuki; Ito, Takashi; Heffner, R. H.; Saha, S. R.*; Koda, Akihiro*; et al.

Physica B; Condensed Matter, 404(5-7), p.749 - 753, 2009/04

 Times Cited Count:4 Percentile:22.79(Physics, Condensed Matter)

Wide varieties of strongly correlated electron phenomena are performed on the stage of a filled skutterudite structure. Especially when one of the players contains a plural number of 4f electrons, the orbital degrees of freedom play a major role as a new type of nonmagnetic and/or weak-magnetic phenomena. Several examples found in Pr- and Sm-based filled skutterudites are introduced in relation to muon spin relaxation experiments.

Journal Articles

Focusing and spectral enhancement of a repetition-rated, laser-driven, divergent multi-MeV proton beam using permanent quadrupole magnets

Nishiuchi, Mamiko; Daito, Izuru; Ikegami, Masahiro; Daido, Hiroyuki; Mori, Michiaki; Orimo, Satoshi; Ogura, Koichi; Sagisaka, Akito; Yogo, Akifumi; Pirozhkov, A. S.; et al.

Applied Physics Letters, 94(6), p.061107_1 - 061107_3, 2009/02

 Times Cited Count:54 Percentile:87.76(Physics, Applied)

A pair of conventional permanent magnet quadrupoles is used to focus a 2.4 MeV laser-driven proton beam at a 1 Hz repetition rate. The magnetic field strengths are 55 T/m and 60 T/m for the first and second quadrupoles respectively. The proton beam is focused to a spot size (full width at half maximum) of 2.7$$times$$8 mm$$^{2}$$ at a distance of 650 mm from the source. This result is in good agreement with a Monte Carlo particle trajectory simulation.

Journal Articles

Pulse radiolysis of sodium formate aqueous solution up to 400 $$^{circ}$$C; Absorption spectra, kinetics and yield of carboxyl radical CO$$_{2}^{cdot}$$$$^{-}$$

Lin, M.; Katsumura, Yosuke; Muroya, Yusa*; He, H.*; Miyazaki, Toyoaki*; Hiroishi, Daisuke*

Radiation Physics and Chemistry, 77(10-12), p.1208 - 1212, 2008/10

 Times Cited Count:22 Percentile:82.38(Chemistry, Physical)

Sodium formate neutral aqueous solutions saturated with N$$_{2}$$O were studied by pulse radiolysis techniques from room temperature to 400 $$^{circ}$$C. The absorption spectra of CO$$_{2}^{cdot}$$$$^{-}$$ show a red shift from $$lambda$$$$_{rm max}$$ = 235 nm at 25 $$^{circ}$$C to 280 nm at 400 $$^{circ}$$C. The second-order decay of CO$$_{2}^{cdot}$$$$^{-}$$ is not monotonically temperature-dependent: the rate constant (2${it k}$/$$varepsilon$$) slightly increases with temperature up to 200 $$^{circ}$$C, then decreases to a valley at 300 $$^{circ}$$C, and it sharply increases again for temperature $$>$$ 350 $$^{circ}$$C. ${it G}$ $$times$$ $$varepsilon$$(CO$$_{2}^{cdot}$$$$^{-}$$) increases with temperature from room temperature to 400 $$^{circ}$$C. Significant density effect on ${it G}$ $$times$$ $$varepsilon$$(CO$$_{2}^{cdot}$$$$^{-}$$) is found at 400 $$^{circ}$$C. Assumed $$varepsilon$$(CO$$_{2}^{cdot}$$$$^{-}$$) is independent on temperature, at 400 $$^{circ}$$C, the density dependence of ${it G}$(CO$$_{2}^{cdot}$$$$^{-}$$) in the presence of N$$_{2}$$O agrees well with that of [${it G}$(e$$_{rm aq}^{-}$$)+${it G}$(H$$^{.}$$)+${it G}$($$^{.}$$OH)].

Journal Articles

Magnetic properties of SmRu$$_{4}$$P$$_{12}$$ probed by $$mu$$SR

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; Sato, Hideyuki*

Journal of Physics and Chemistry of Solids, 68(11), p.2072 - 2075, 2007/11

 Times Cited Count:1 Percentile:7.92(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Muon spin relaxation and hyperfine-enhanced $$^{141}$$Pr nuclear spin dynamics in Pr(Os,Ru)$$_4$$Sb$$_{12}$$ and (Pr,La)Os$$_4$$Sb$$_{12}$$

Shu, L.*; MacLaughlin, D. E.*; Aoki, Yuji*; Tsunashima, Yoshino*; Yonezawa, Yuki*; Sanada, Shotaro*; Kikuchi, Daisuke*; Sato, Hideyuki*; Heffner, R. H.; Higemoto, Wataru; et al.

Physical Review B, 76(1), p.014527_1 - 014527_8, 2007/07

 Times Cited Count:20 Percentile:65.43(Materials Science, Multidisciplinary)

Journal Articles

Evolution of local magnetic state in SmRu$$_4$$P$$_{12}$$ probed by muon spin relaxation

Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki; Fujimoto, Tatsuya*; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; et al.

Journal of the Physical Society of Japan, 76(5), p.053707_1 - 053707_4, 2007/05

 Times Cited Count:27 Percentile:76.48(Physics, Multidisciplinary)

A filled skutterudite compound SmRu$$_4$$P$$_{12}$$ shows metal-insulatortransition at $$T_{rm MI}$$=16.5K with magnetic anomaly. A possibility of magnetic octupole ordering has been discussed on the basis of multipole degrees of freedom belonging to thecrystalline-electric-field ground state. We investigated local magnetic states in the ordered state by using the muon spin relaxation method. An increase of muon spin relaxation rate was detected in zeroapplied field just below $$T_{rm MI}$$, indicating time-reversal-symmetry breaking in the ordered state. This result suggests that the order parameter includes magnetic octupole and/ordipole. Magnitude of the internal field at the muon site monotonically increases with decreasing temperature, growing steeply below $$T^{prime}$$=3K. The longitudinal relaxation rate has a maximum at around $$T^{prime}$$, suggesting suppression of magnetic fluctuations. We discussed these experimental facts on the basis of the multipoledegrees of freedom.

Journal Articles

Knight shift measurements in the superconducting state of Pr$$_{1-x}$$La$$_x$$Os$$_4$$Sb$$_{12}$$ (X=0.4) probed by $$mu$$SR

Higemoto, Wataru; Aoki, Yuji*; Oishi, Kazuki; Ito, Takashi; Heffner, R. H.; Saha, S. R.*; Koda, Akihiro*; Sato, Hideyuki*; Kadono, Ryosuke*; Kikuchi, Daisuke*; et al.

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.620 - 622, 2007/03

no abstracts in English

Journal Articles

Characterization of preformed plasmas using a multi-dimensional hydrodynamic simulation code in the study of high-intensity laser-plasma interactions

Sagisaka, Akito; Utsumi, Takayuki*; Daido, Hiroyuki; Ogura, Koichi; Orimo, Satoshi; Takai, Mamiko; Hayashi, Yukio; Mori, Michiaki; Yogo, Akifumi; Kado, Masataka; et al.

Journal of Plasma Physics, 72(6), p.1281 - 1284, 2006/12

 Times Cited Count:0 Percentile:0.01(Physics, Fluids & Plasmas)

no abstracts in English

44 (Records 1-20 displayed on this page)