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structure transition under high pressureYamanaka, Takamitsu*; Nakamoto, Yuki*; Sakata, Masafumi*; Shimizu, Katsuya*; Hattori, Takanori
Physics and Chemistry of Minerals, 51(1), p.4_1 - 4_10, 2024/02
Times Cited Count：0 Percentile：0.16(Materials Science, Multidisciplinary)Neutron and synchrotron X-ray diffraction and electric conductivity measurements of FeTiO ilmenite were performed under pressures. Ilmenite structure is retained up to 28 GPa. Structure analysis revealed that FeO
and TiO are compressible and less compressible below 8 GPa, respectively. The resistivity is lowest along the Fe-Ti direction that has shortest interatomic distance among all the metal ion pairs. The resistivity in the direction normal to c-axis monotonically decreases with pressure, whereas that along c-axis shows hallow-shape with pressure. Maximum entropy analysis shows that electron configuration of Fe
(3
) is more strongly changed than Ti
(3
) under compression. The anisotropic electrical conductivity and non-uniform structure change of Fe-Ti interatomic distance can be explained by the possible spin transition from high-spin state to intermediate-spin state of Fe cation.
conditions & electrical transport and structural properties of FeH
Matsuoka, Takehiro*; Hirao, Naohisa*; Oishi, Yasuo*; Shimizu, Katsuya*; Machida, Akihiko; Aoki, Katsutoshi
Koatsuryoku No Kagaku To Gijutsu, 21(3), p.190 - 196, 2011/09
We present the newly developed electrical resistance measurement technique for metal hydrides compressed in high-pressure H and the first successful 
simultaneous measurements of electrical resistance and X-ray diffraction of FeH at high pressures and low temperatures. The electrical resistivity 
showed a sharp increase with the formation of iron-hydride FeH (
) at 3.5 GPa. The 
'-phase of FeH was found to be metallic up to 25.5 GPa. The vs. 
curves up to 16.5 GPa approximately follow Fermi-liquid law below 25 K. However, 
was found to be better fitting at 25.5 GPa. This change can be related to the previously reported ferromagnetism collapse at corresponding pressures.
Matsuoka, Takahiro*; Fujihisa, Hiroshi*; Hirao, Naohisa*; Oishi, Yasuo*; Mitsui, Takaya; Masuda, Ryo; Seto, Makoto*; Yoda, Yoshitaka*; Shimizu, Katsuya*; Machida, Akihiko; et al.
Physical Review Letters, 107(2), p.025501_1 - 025501_4, 2011/07
Times Cited Count：29 Percentile：77.56(Physics, Multidisciplinary)Europium-hydride EuH
exposed to high-pressure H conditions has been found to exhibit structural and valence changes, 
(
=2, divalent) 
63/
(=2, 7.2-8.7 GPa) 
4/
(
2, 8.7-9.7 GPa) 4/
(2, 9.7 GPa-, trivalent). Having trivalent character and distorted cubic fcc structure, the 4/ structure is the 
-phase which has been commonly observed for other rare-earth metal hydrides. Our study clearly demonstrates that EuH is no longer an "irregular" member of the rare earth metal hydrides.
M
asson, M.-A.*; Muranaka, Hiroshi*; Matsuda, Tatsuma; Kawai, Tomoya*; Haga, Yoshinori; Knebel, G.*; Aoki, Dai*; Lapertot, G.*; Honda, Fuminori*; Settai, Rikio*; et al.
Physica C, 470(Suppl.1), p.S536 - S538, 2010/12
Times Cited Count：4 Percentile：21.9(Physics, Applied)
AlHonda, Fuminori*; Masson, M.-A.*; Nakano, Yasunori*; Yoshitani, Naohisa*; Yamamoto, Etsuji; Haga, Yoshinori; Takeuchi, Tetsuya*; Yamagami, Hiroshi*; Shimizu, Katsuya*; Settai, Rikio*; et al.
Journal of the Physical Society of Japan, 77(4), p.043701_1 - 043701_4, 2008/04
Times Cited Count：38 Percentile：81.62(Physics, Multidisciplinary)Nakashima, Miho*; Ueda, Taiki*; Shimizu, Katsuya*; Nakashima, Hiroshi*; Thamizhavel, A.*; Tateiwa, Naoyuki; Haga, Yoshinori; Hedo, Masato*; Uwatoko, Yoshiya*; Settai, Rikio*; et al.
Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.e9 - e11, 2007/03
We measured the electrical resistivity and AC-specific heat for a canted ferromagnet CePtAl under pressures using a diamond-anvilpressure cell. With increasing pressure, the magnetic ordering temperature 
increases monotonously, becomes constant above 8 GPa and then starts to decrease steeply in a narrow pressure region from 10.3 to 10.9 GPa, indicating the first-order like phase transition. The similar pressure dependence of was obtained in the AC-specific heat measurement.
-Mn under high pressureMiyake, Atsushi*; Kanemasa, Tsunehiro*; Yagi, Ryohei*; Kagayama, Tomoko*; Shimizu, Katsuya*; Haga, Yoshinori; Onuki, Yoshichika
Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.e222 - e224, 2007/03
We have measured electrical resistivity of single crystalline -manganese (-Mn) under high pressure. -Mn shows an antiferromagnetic ordering at 
= 95 K and has four inequivalent crystal sites with different magnetic moments. With increasing pressure, shifts toward lower temperature. At higher pressure, the shape of anomaly at changes to a kink-like one, which may indicate different magnetic ordering from that at lower pressure. Such a difference between lower and higher pressure regions is considered to be caused by the four inequivalent magnetic moments in -Mn. At 1.9 GPa, the boundary of the ordered phases, we observe a sudden decrease of the residual resistivity and a peak of the A-coefficient of 
-term of the resistivity.
(
3) under high pressureMatsuoka, Takehiro*; Kitayama, Takayasu*; Shimizu, Katsuya*; Nakamoto, Yuki*; Kagayama, Tomoko*; Aoki, Katsutoshi; Oishi, Yasuo*; Takemura, Kenichi*
High Pressure Research, 26(4), p.391 - 394, 2006/12
Times Cited Count：3 Percentile：26.52(Physics, Multidisciplinary)The electrical and structural properties of yttrium hydride YHx was studied by the in-situ measurements of the electrical resistance and X-ray diffraction up to 86 GPa. The electrical resistivity increased with applying pressure up to 10 GPa and showed a maximum which accompanied with the structural transition of metal lattice from hcp to fcc structure. In fcc phase the resistivity decreased significantly, however the value still remained larger by 4 orders of magnitude that that of pure yttrium metal. We could not confirm the insulator to metal transition up to 23 GPa. The resistivity showed another maximum in the large pressure region 40 60 GPa without the structural phase transition of metal lattice.
Shimizu, Hiroyasu*; Utsumi, Wataru; Kume, Tetsuji*; Kondo, Tadashi*; Shimizu, Katsuya*; Sotani, Tomohiro*; Taniguchi, Takashi*; Nakamura, Kazutaka*
Koatsuryoku No Kagaku To Gijutsu, 11(4), p.334 - 338, 2001/12
no abstracts in English
*; M.I.Eremets*; *; *; *
Journal of the Physical Society of Japan, 66(9), p.2564 - 2565, 1997/09
Times Cited Count：53 Percentile：92.59(Physics, Multidisciplinary)no abstracts in English
Matsuoka, Takehiro*; Shimizu, Katsuya*; Fujihisa, Hiroshi*; Hirao, Naohisa*; Oishi, Yasuo*; Yoda, Yoshitaka*; Mitsui, Takaya; Masuda, Ryo; Machida, Akihiko; Aoki, Katsutoshi; et al.
no journal, ,
Europium-hydride EuH exposed to high-pressure H conditions has been studied by X-ray diffraction and M
ssbauer spectroscopy measurements up to 50 GPa using synchrotron radiation. We report new structural and valence transitions, Pnma(x=2, divalent) P63/mmc(x=2, 7.2-8.7GPa) I4/m(x2, 8.7-9.7 GPa) I4/mmm(x2, 9.7 GPa, trivalent). The phase of I4/mmm having trivalent character is a small distortion from cubic fcc structure which has been commonly observed for -phase of all other trivalent rare-earth metal hydrides. Our study clearly demonstrates the first observation of -phase of EuH and suggest that the material is no longer an irregular member of the rare earth metal hydrides RH systems.
