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Journal Articles

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex, 2; Neutron scattering instruments

Nakajima, Kenji; Kawakita, Yukinobu; Ito, Shinichi*; Abe, Jun*; Aizawa, Kazuya; Aoki, Hiroyuki; Endo, Hitoshi*; Fujita, Masaki*; Funakoshi, Kenichi*; Gong, W.*; et al.

Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.

Journal Articles

Science from the initial operation of HRC

Ito, Shinichi*; Yokoo, Tetsuya*; Masuda, Takatsugu*; Yoshizawa, Hideki*; Soda, Minoru*; Ikeda, Yoichi*; Ibuka, Soshi*; Kawana, Daichi*; Sato, Taku*; Nambu, Yusuke*; et al.

JPS Conference Proceedings (Internet), 8, p.034001_1 - 034001_6, 2015/09

Journal Articles

Disproportionation reaction of LaH$$_2$$ at high pressure and low temperature

Machida, Akihiko; Watanuki, Tetsu; Kawana, Daichi*; Aoki, Katsutoshi

Journal of Physics; Conference Series, 500(2), p.022001_1 - 022001_5, 2014/05

 Times Cited Count:0 Percentile:0.03

We found that LaH$$_2$$ decomposed into two different molar-volume phases at 11 GPa at room temperature through synchrotron radiation X-ray diffraction (SR-XRD) measurements. Observed decomposition suggests that the H-poor and H-rich phases are spontaneously formed by pressurization, namely, a pressure-induced disproportionation reaction. Observed disproportionation reaction accompanies the transfer of the H atoms between the interstitial sites. Diffusivity of the H atoms suppresses as the temperature decreases. Hence we have investigated this disproportionation of LaH$$_2$$ in the low H diffusivity case at low temperature.SR-XRD measurements at high pressure and low temperature were carried out at BL22XU, SPring-8. We found the disproportionation at 13.5 GPa even at 200 K. The volume fraction of the H-poor phase at 200 K is larger than that at room temperature. The disproportionation at low temperature will be discussed on the basis of the X-ray diffraction data.

Journal Articles

Intermediate-valence icosahedral Au-Al-Yb quasicrystal

Watanuki, Tetsu; Kashimoto, Shiro*; Kawana, Daichi*; Yamazaki, Teruo*; Machida, Akihiko; Tanaka, Yukinori*; Sato, Taku*

Physical Review B, 86(9), p.094201_1 - 094201_6, 2012/09

 Times Cited Count:56 Percentile:89.52(Materials Science, Multidisciplinary)

A quasiperiodic, intermediate-valence (IV) system is realized in an icosahedral Au-Al-Yb quasicrystal. X-ray absorption spectroscopy near the Yb $$L$$$$_{3}$$-edge indicates that quasiperiodically arranged Yb ions assume a mean valence of 2.61, between a divalent state (4$$f$$$$^{14}$$, $$J$$ = 0) and a trivalent one (4$$f$$$$^{13}$$, $$J$$ = 7/2). Magnetization measurements demonstrate that the 4$$f$$ holes in this quasicrystal have a localized character. The magnetic susceptibility shows a Curie-Weiss behavior above $$sim$$100 K with an effective magnetic moment of 3.81 $$mu$$$$_{rm B}$$ per Yb. Moreover, a crystalline approximant to this quasicrystal is an IV compound. We propose a heterogeneous IV model for the quasicrystal, whereas the crystalline approximant is most likely a homogeneous IV system. At temperatures below $$sim$$10 K, specific heat and magnetization measurements reveal non-Fermi-liquid behavior in both the quasicrystal and its crystalline approximant without either doping, pressure, or field tuning.

Journal Articles

Pressure-induced formation of intermediate-valence quasicrystalline systems in Yb-based alloys

Watanuki, Tetsu; Kawana, Daichi*; Machida, Akihiko; Tsai, A. P.*

Hoshako, 25(3), p.176 - 183, 2012/05

Quasiperiodic intermediate-valence systems were prepared by applying pressure to Yb-based quasicrystals. In these systems, each quasiperiodic lattice point has a charge degree of freedom. Synchrotron radiation X-ray absorption spectroscopy experiments near the Yb $$L_3$$-edge demonstrate that the Yb valence in a Cd-Yb icosahedral quasicrystal increases continuously upon compression from a divalent state at ambient pressure and reaches 2.33 at 31.7 GPa, where the quasiperiodically arranged Yb ions take a valence fluctuation state. For the case of a Cd-Mg-Yb icosahedral quasicrystal, the Yb valence reaches a value of 2.71 at 57.6 GPa. By following the trend of Yb-based intermediate-valence crystalline compounds, this large valence increase suggests that the 4f electron system in this quasicrystal varies from a valence fluctuation regime to a strong correlated electron regime.

Journal Articles

Pressure-induced formation of intermediate-valence quasicrystalline system in a Cd-Mg-Yb alloy

Watanuki, Tetsu; Kawana, Daichi*; Machida, Akihiko; Tsai, A. P.*

Physical Review B, 84(5), p.054207_1 - 054207_6, 2011/08

 Times Cited Count:10 Percentile:43.79(Materials Science, Multidisciplinary)

A quasiperiodic intermediate-valence system was prepared by applying pressure to an icosahedral Cd-Mg-Yb quasicrystal. X-ray absorption spectroscopy near the Yb $$L$$$$_{3}$$-edge demonstrates that the Yb valence increases continuously upon compression from the divalent state (4$$f$$$$^{14}$$) at ambient pressure and reaches a value of 2.71 at 57.6 GPa, which is close to the trivalent state (4$$f$$$$^{13}$$). By following the trend of Yb-based intermediate-valence crystalline compounds, this large valence increase suggests the change of 4$$f$$ character in the Cd-Mg-Yb quasicrystal from an itinerant state with weak electron correlations to an intermediate region between an itinerant and a localized state with strong correlations.

Journal Articles

Intermediate-valence quasicrystals in Yb-based alloys under pressure

Watanuki, Tetsu; Kawana, Daichi*; Machida, Akihiko; Tsai, A. P.*

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA087_1 - SA087_3, 2011/07

 Times Cited Count:5 Percentile:40.38(Physics, Multidisciplinary)

A quasiperiodic intermediate-valence system is demonstrated by applying pressure to an icosahedral Cd-Mg-Yb quasicrystal as well as our previous report on a Cd-Yb quasicrystal. Yb $$L$$$$_{rm III}$$-edge X-ray absorption spectroscopy experiments demonstrate that the Yb valence increases continuously upon compression from the divalent state at ambient pressure, and reaches a valence of 2.37 at 16.3 GPa. Unlike other known quasicrystals, these Yb-based quasiperiodic intermediate-valence systems have the following two characteristics. (1) Each quasiperiodic lattice point has a charge degree of freedom, and (2) pressure can control the strength of the electron correlations.

Journal Articles

Phase separation of lanthanum hydride under high pressure

Machida, Akihiko; Watanuki, Tetsu; Kawana, Daichi; Aoki, Katsutoshi

Physical Review B, 83(5), p.054103_1 - 054103_6, 2011/02

 Times Cited Count:21 Percentile:63.39(Materials Science, Multidisciplinary)

Structural change of lanthanum dihydride, which has an fcc metal lattice with tetrahedral interstitial sites fully occupied with hydrogen atoms and empty octahedral sites, has been investigated at high pressures up to 20 GPa at ambient temperature by synchrotron radiation X-ray diffraction. The coexistence state of two fcc metal lattices observed above 11 GPa is interpreted in terms of phase separation from the dihydride toward a solid solution and trihydride states, in both of which the octahedral interstitial sites are partially occupied with hydrogen atoms. A gradual distortion from the cubic to a tetragonal lattice is observed prior to the phase separation. The coexistence phase goes back to the dihydride fcc phase via the lattice distorted phase with decreasing pressure.

Journal Articles

Intermediate-valence quasicrystal of a Cd-Yb alloy under pressure

Kawana, Daichi*; Watanuki, Tetsu; Machida, Akihiko; Shobu, Takahisa; Aoki, Katsutoshi; Tsai, A. P.*

Physical Review B, 81(22), p.220202_1 - 220202_4, 2010/06

 Times Cited Count:16 Percentile:58.53(Materials Science, Multidisciplinary)

A quasiperiodic intermediate-valence system was prepared by applying pressure to an icosahedral Cd-Yb quasicrystal. In this system, each quasiperiodic lattice point has a charge degree of freedom. Yb $$L$$$$_{rm III}$$ X-ray absorption spectroscopy experiments demonstrate that the Yb valence increases continuously upon compression from a divalent state at ambient pressure and reaches 2.33 at 31.7 GPa. A comparison study to the crystalline approximant suggests that the quasiperiodically arranged Yb ions have a homogeneous intermediate valence that takes a valence fluctuation state under pressure.

Journal Articles

Formation and crystal growth process of AlH$$_{3}$$ in Al-H system

Saito, Hiroyuki; Okajima, Yuka; Yoneda, Yasuhiro; Machida, Akihiko; Kawana, Daichi; Watanuki, Tetsu; Katayama, Yoshinori; Aoki, Katsutoshi

Journal of Alloys and Compounds, 496(1-2), p.L25 - L28, 2010/04

 Times Cited Count:20 Percentile:69.87(Chemistry, Physical)

Journal Articles

Pressure-induced antiferromagnetic order in filled skutterudite PrFe$$_{4}$$P$$_{12}$$ studied by single-crystal high-pressure neutron diffraction

Osakabe, Toyotaka; Kuwahara, Keitaro*; Kawana, Daichi*; Iwasa, Kazuaki*; Kikuchi, Daisuke*; Aoki, Yuji*; Kogi, Masafumi*; Sato, Hideyuki*

Journal of the Physical Society of Japan, 79(3), p.034711_1 - 034711_7, 2010/03

 Times Cited Count:17 Percentile:67.53(Physics, Multidisciplinary)

Journal Articles

Development of a hybrid-anvil type high-pressure device and its application to magnetic neutron scattering studies

Osakabe, Toyotaka; Kakurai, Kazuhisa; Kawana, Daichi*; Kuwahara, Keitaro*

Journal of Magnetism and Magnetic Materials, 310(2, Part3), p.2725 - 2727, 2007/03

no abstracts in English

Journal Articles

Structural transformation on the pressure-induced metal-insulator transition in PrFe$$_{4}$$4P$$_{12}$$

Kawana, Daichi*; Kuwahara, Keitaro*; Sato, Masashi*; Takagi, Masatoshi*; Aoki, Yuji*; Kogi, Masafumi*; Sato, Hideyuki*; Sagayama, Hajime*; Osakabe, Toyotaka; Iwasa, Kazuaki*; et al.

Journal of the Physical Society of Japan, 75(11), p.113602_1 - 113602_4, 2006/11

 Times Cited Count:11 Percentile:57.14(Physics, Multidisciplinary)

We report the first X-ray diffraction experiments of PrFe$$_{4}$$P$$_{12}$$ under high pressure. We discovered a symmetry lowering from cubic to orthorhombic or lower at the metal-insulator transition temperature, accompanied by a jump in the lattice constant, which indicates a first-order phase transition. The superlattice reflections at q=(1,0,0) observed in the low-pressure nonmagnetic ordered phase are found to disappear in the insulating phase. The temperature dependence of the lattice constant and the absence of the superlattice reflections are well explained by taking into account an antiferromagnetic ordering.

Journal Articles

High-pressure apparatus for magnetic neutron diffraction beyond 3 GPa at low temperature

Osakabe, Toyotaka; Kogi, Masafumi*; Kawana, Daichi*; Hannan, A.*; Soyama, Kazuhiko; Kitazawa, Hideaki*

Journal of Magnetism and Magnetic Materials, 272-276, p.2157 - 2158, 2004/05

 Times Cited Count:3 Percentile:20.33(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Magnetic ${it P}$-${it T}$ phase diagrams of CeSb and CeBi

Osakabe, Toyotaka; Hannan, A.*; Kawana, Daichi*; Kogi, Masafumi*; Kitazawa, Hideaki*

Acta Physica Polonica B, 34(2), p.1469 - 1472, 2003/02

no abstracts in English

Oral presentation

Single-crystal neutron diffraction on the pressure-induced insulating phase of PrFe$$_{4}$$P$$_{12}$$

Kawana, Daichi*; Osakabe, Toyotaka; Kuwahara, Keitaro*; Kikuchi, Daisuke*; Aoki, Yuji*; Kogi, Masafumi*; Sato, Hideyuki*

no journal, , 

no abstracts in English

Oral presentation

Single-crystal neutron diffraction on the pressure-induced insulating phase of PrFe$$_{4}$$P$$_{12}$$, 2

Osakabe, Toyotaka; Kawana, Daichi*; Kuwahara, Keitaro*; Iwasa, Kazuaki*; Kikuchi, Daisuke*; Aoki, Yuji*; Kogi, Masafumi*; Sato, Hideyuki*

no journal, , 

no abstracts in English

Oral presentation

Structural deformation of Cd-Yb quasicrystal under high pressure and low temperature

Watanuki, Tetsu; Machida, Akihiko; Aoki, Katsutoshi; Kawana, Daichi; Sato, Taku*; Tsai, A. P.*

no journal, , 

no abstracts in English

Oral presentation

Pressure-induced magnetic order of filled skutterudite compound PrFe$$_{4}$$P$$_{12}$$

Osakabe, Toyotaka; Kuwahara, Keitaro*; Kawana, Daichi; Iwasa, Kazuaki*

no journal, , 

Filled skutterudite compound PrFe$$_{4}$$P$$_{12}$$ shows the non-magnetic phase transition at T$$_{A}$$=6.5 K. Recent NMR measurements and theoretical works have predicted that the order parameter of the non-magnetic phase is the $$Gamma$$$$_{1}$$-type antiferro-quadropole. Under pressure above 2.5 GPa, the non-magnetic phase disappears and the new insulating phase appears, for example, below 9 K at 3.2 GPa. We have performed neutron diffraction experiments under pressure above 3 GPa using the triple-axis spectrometer TAS-1 installed at 2G beam port of JRR-3M in JAEA at Tokai in order to elucidate the order parameter of the pressure-induced insulating phase. We have successfully observed the distinct magnetic Bragg peak at (1,0,0) reciprocal lattice point at 3.2 GPa in the insulating phase. The peak corresponds to an antiferromagnetic long-range ordering of q = (1,0,0). The magnetic moments are 2.0 $$mu_{rm B}$$ /Pr ions, which are align along the [0,0,1] direction. The results indicate that the insulating phase corresponds to the antiferromagnetically orderd phase and the order parameter is switched from the non-magnetic antiferro-quadropole to the antiderro-magnetic dipole by the pressurization of the lattice contraction of $$Delta$$L/L$$sim$$0.5.

Oral presentation

Pressure dependence of Yb valence in Cd-Yb quasicrystal

Kawana, Daichi; Watanuki, Tetsu; Machida, Akihiko; Shobu, Takahisa; Aoki, Katsutoshi; Tsai, A. P.*

no journal, , 

no abstracts in English

60 (Records 1-20 displayed on this page)