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Katayama, Yoshinori; Hattori, Takanori; Saito, Hiroyuki; Aoki, Katsutoshi; Funakoshi, Kenichi*; Tange, Yoshinori*
no journal, ,
Liquid water at ambient conditions shows unique properties because of hydrogen-bonded network structure. We conducted high-pressure high-temperature X-ray diffraction experiments up to 17 GPa at the SPring-8 synchrotron radiation facility and reported that the local structure changed towards a simple liquid-like structure through an increase of coordination number. We have extended the pressure range to 20 GPa and the results will be reported. However these data were measured just above the melting temperature at each pressure so that the effect of pressure (density) and that of temperature could not be separated. In this work, we have conducted X-ray diffraction measurement at various temperatures near 1 GPa. The shoulder of the first peak in S(Q) vanished at 200 
C and the first peak became symmetric at 600 C. This result suggests a structural change from a low coordinated structure to a simple liquid-like structure.
O
at high pressures and temperaturesSaito, Hiroyuki; Utsumi, Wataru; Aoki, Katsutoshi
no journal, ,
no abstracts in English
Machida, Akihiko; Watanuki, Tetsu; Omura, Ayako*; Aoki, Katsutoshi
no journal, ,
We have investigated the structural properties of yttrium dihydrides, YH, by synchrotron radiation X-ray diffraction measurements under high pressure. RH exhibit the fcc metal lattice, which contains two interstitial hydrogen atoms, which are located at the tetrahedral sites, par one metal atom. These YH have no hydrogen atom at octahedral site. Then, it is expected that the high-pressure structural properties of the YH differ from the YH
. The YH sample was pressurized with He pressure medium. we have found that the second phase appeared at about 36 GPa. We will discussed the observed pressure-induced phase separation in YH.
under high pressureTateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Miyauchi, Yuichiro*; Okuda, Yusuke*; Settai, Rikio*; Onuki, Yoshichika
no journal, ,
Recently, non-centrosymmetric superconductors have attracted much attention from a view point of a mixed parity of a superconducting pair wave function. CeIrSi crystalizes in the tetragonal BaNiSn-type crystal structure. It shows an antiferromagnetic ordering at 
= 5.0 K and becomes a superconductor above 2 GPa. In this study, we have investigated CeIrSi by measurements of the heat capacity and electrical resistivity under high pressure. We will discuss the bulk superconducting phase.
Tateiwa, Naoyuki; Haga, Yoshinori; Ikeda, Shugo; Yamamoto, Etsuji; Onuki, Yoshichika
no journal, ,
We have started the high pressure study on the actinide compound by the diamond anvil cell (DAC). We focus on uranium antiferromagnets. There have been a few studies on the quantum critical point of uranium antiferromagnets, compared with Ce-based antiferromagnets such as CeIn where the pressure-induced superconductivity appears around the quantum critical point. We study a heavy fermion uranium antiferromagnet UZn
whose the linear heat capacity coefficient is about 500 mJ/molK
. In this presentation, we will show experimental results as well as our high pressure system.
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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/L
0.5.
Hattori, Takanori; Tsuji, Kazuhiko*
no journal, ,
In spite of its importance, the partial structures for liquid alloys have not been investigated even at ambient pressure. The structures which differentiate the chemical environment around each element, i.e., chemical short-range order, is inevitable for discussing the local structure and its stability in disordered materials. Furthermore, the chemical short-range order reflects the chemical bonding in liquid, so it gives us the information on chemical bonding states in liquid. We have applied anomalous X-ray scattering method to the liquid under high pressure. In the previous conference, we introduced the results on liquid AgI at relatively low pressures. In this conference, we introduce the results at higher pressures.