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

https://doi.org/10.3390/qubs1030009

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.

Disproportionation reaction of LaH 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

https://doi.org/10.1088/1742-6596/500/2/022001

We found that LaH 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 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.

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

https://cir.nii.ac.jp/crid/1570291225847897728

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 -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.

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

https://doi.org/10.1143/JPSJS.80SA.SA087

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 -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.

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

https://doi.org/10.1103/PhysRevB.81.220202

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 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.

Pressure-induced antiferromagnetic order in filled skutterudite PrFeP 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

https://doi.org/10.1143/JPSJ.79.034711

Structural transformation on the pressure-induced metal-insulator transition in PrFe4P

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

https://doi.org/10.1143/JPSJ.75.113602

We report the first X-ray diffraction experiments of PrFeP 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.

Magnetic - 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

http://www.actaphys.uj.edu.pl/_cur/store/vol34/pdf/v34p1469.pdf

no abstracts in English

Single-crystal neutron diffraction on the pressure-induced insulating phase of PrFeP, 2

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

no journal, , 

no abstracts in English

Pressure-induced magnetic order of filled skutterudite compound PrFeP

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

no journal, , 

Filled skutterudite compound PrFeP shows the non-magnetic phase transition at T=6.5 K. Recent NMR measurements and theoretical works have predicted that the order parameter of the non-magnetic phase is the -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 /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 L/L0.5.