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Journal Articles

High-pressure radiative conductivity of dense silicate glasses with potential implications for dark magmas

Murakami, Motohiko*; Goncharov, A. F.*; Hirao, Naohisa*; Masuda, Ryo*; Mitsui, Takaya; Thomas, S. M.*; Bina, C. R.*

Nature Communications (Internet), 5, p.5428_1 - 5428_6, 2014/11

 Times Cited Count:12 Percentile:48.43(Multidisciplinary Sciences)

Journal Articles

The Spin state of iron in Fe$$^{3+}$$-bearing Mg-perovskite and its crystal chemistry at high pressure

Mashimo, Izumi*; Otani, Eiji*; Hirao, Naohisa*; Mitsui, Takaya; Masuda, Ryo*; Seto, Makoto*; Sakai, Takeshi*; Takahashi, Suguru*; Nakano, Satoshi*

American Mineralogist, 99(8-9), p.1555 - 1561, 2014/08

 Times Cited Count:4 Percentile:78.53(Geochemistry & Geophysics)

Journal Articles

In situ synchrotron $$^{57}$$Fe M$"o$ssbauer spectroscopy of RFe$$_{2}$$ (R = Y, Gd) hydrides synthesized under ultra-high-pressure hydrogen

Mitsui, Takaya; Masuda, Ryo*; Seto, Makoto; Hirao, Naohisa*; Matsuoka, Takehiro*; Nakamura, Yumiko*; Sakaki, Koji*; Enoki, Hirotoshi*

Journal of Alloys and Compounds, 580(Suppl.1), p.S264 - S267, 2013/12

 Times Cited Count:3 Percentile:70.89(Chemistry, Physical)

Journal Articles

Synchrotron radiation $$^{57}$$Fe-M$"o$ssbauer spectroscopy using nuclear monochromator

Mitsui, Takaya; Masuda, Ryo; Hirao, Naohisa*; Mibu, Ko*; Seto, Makoto

Hyperfine Interactions, 204(1-3), p.97 - 100, 2012/04

 Times Cited Count:1 Percentile:34.1

Journal Articles

Electrical resistance measurement techniques for metal hydrides under high-pressure H$$_2$$ conditions & electrical transport and structural properties of FeH$$_x$$

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$$_2$$ and the first successful ${it in-situ}$ simultaneous measurements of electrical resistance and X-ray diffraction of FeH at high pressures and low temperatures. The electrical resistivity $$rho$$ showed a sharp increase with the formation of iron-hydride FeH$$_x$$ ($$xsim1$$) at 3.5 GPa. The $$epsilon$$'-phase of FeH was found to be metallic up to 25.5 GPa. The $$rho$$ vs. $$T$$ curves up to 16.5 GPa approximately follow Fermi-liquid law below 25 K. However, $$T^5$$ was found to be better fitting at 25.5 GPa. This change can be related to the previously reported ferromagnetism collapse at corresponding pressures.

Journal Articles

Structural and valence changes of europium hydride induced by application of high-pressure H$$_{2}$$

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:18 Percentile:27.99(Physics, Multidisciplinary)

Europium-hydride EuH$$_{x}$$ exposed to high-pressure H$$_{2}$$ conditions has been found to exhibit structural and valence changes, $$Pnma$$ ($$x$$=2, divalent) $$rightarrow$$ $$P$$63/$$mmc$$ ($$x$$=2, 7.2-8.7 GPa) $$rightarrow$$ $$I$$4/$$m$$ ($$x$$$$>$$2, 8.7-9.7 GPa) $$rightarrow$$ $$I$$4/$$mmm$$ ($$x$$$$>$$2, 9.7 GPa-, trivalent). Having trivalent character and distorted cubic fcc structure, the $$I$$4/$$mmm$$ structure is the $$beta$$-phase which has been commonly observed for other rare-earth metal hydrides. Our study clearly demonstrates that EuH$$_{x}$$ is no longer an "irregular" member of the rare earth metal hydrides.

Journal Articles

Ultrahigh-pressure measurement in the multimegabar range by energy-domain synchrotron radiation $$^{57}$$Fe-M$"o$ssbauer spectroscopy using focused X-rays

Mitsui, Takaya; Seto, Makoto; Hirao, Naohisa*; Oishi, Yasuo*; Kobayashi, Yasuhiro*; Higashitaniguchi, Satoshi*; Masuda, Ryo*

Japanese Journal of Applied Physics, Part 2, 46(16), p.L382 - L384, 2007/04

 Times Cited Count:9 Percentile:60.6(Physics, Applied)

Energy-domain synchrotron radiation M$"o$ssbauer spectroscopy was performed by a single-line M$"o$ssbauer filtering technique and focusing X-ray optics. Pure nuclear Bragg reflection from a heated $$^{57}$$FeBO$$_{3}$$ single crystal was used for a neV order bandwidth ultrahigh energy resolution X-ray analyzer. As an example of small target research, the M$"o$ssbauer transmission spectrum of polycrystalline iron metal was observed using a diamond anvil cell at multimegabar pressures (252 GPa) for the first time.

Journal Articles

Generation and application of ultrahigh monochromatic X-ray using high-quality $$^{57}$$FeBO$$_{3}$$ single crystal

Mitsui, Takaya; Seto, Makoto; Kikuta, Seishi*; Hirao, Naohisa*; Oishi, Yasuo*; Takei, Fumihiko*; Kobayashi, Yasuhiro*; Kitao, Shinji*; Higashitaniguchi, Satoshi*; Masuda, Ryo*

Japanese Journal of Applied Physics, Part 1, 46(2), p.821 - 825, 2007/02

 Times Cited Count:23 Percentile:31.96(Physics, Applied)

Ultrahigh monochromatic 14.4 keV X-rays with a narrow bandwidth of 15.4 neV were generated successfully with a high counting rate of 12,000 counts/s at the undulator beamline (BL11XU) of SPring-8. It was achieved by combining an intense X-ray from the third generation synchrotron radiation facility SPring-8 and pure nuclear Bragg scattering of a very highquality $$^{57}$$FeBO$$_{3}$$ perfect single crystal at the N$'e$el temperature. We describe the detailed study of the beam characteristics and some performance test experiments of energy-domain synchrotron radiation M$"o$ssbauer spectroscopy, including a highpressure experiment using a diamond anvil cel.

Oral presentation

Development of neV spectroscopy using synchrotron radiation

Mitsui, Takaya; Seto, Makoto; Masuda, Ryo*; Kobayashi, Yasuhiro*; Kitao, Shinji*; Hirao, Naohisa*

no journal, , 

no abstracts in English

Oral presentation

Synchrotron radiation M$"o$ssbauer micro-spectroscopy using ultra fine monochromatic X-rays

Mitsui, Takaya; Seto, Makoto; Kobayashi, Yasuhiro*; Kitao, Shinji*; Masuda, Ryo*; Hirao, Naohisa*

no journal, , 

no abstracts in English

Oral presentation

Ultra high pressure synchrotron radiation M$"o$ssbauer spectroscopy at multimegabar pressures

Mitsui, Takaya; Seto, Makoto; Kobayashi, Yasuhiro*; Hirao, Naohisa*

no journal, , 

no abstracts in English

Oral presentation

Ultrahigh-pressure SR M$"{o}$ssbauer spectroscopy of GdFe$$_{2}$$

Mitsui, Takaya; Seto, Makoto; Masuda, Ryo; Hirao, Naohisa*

no journal, , 

no abstracts in English

Oral presentation

Ultrahigh-pressure synchrotron radiation Mossbauer spectroscopy of hydrogen-induced amorphous GdFe$$_{2}$$

Mitsui, Takaya; Seto, Makoto; Hirao, Naohisa*; Masuda, Ryo

no journal, , 

no abstracts in English

Oral presentation

In-situ ultrahigh hydrogen pressure M$"o$ssbauer spectroscopy on the metal hydrides

Mitsui, Takaya; Seto, Makoto; Masuda, Ryo; Hirao, Naohisa*; Matsuoka, Takahiro*

no journal, , 

no abstracts in English

Oral presentation

Synchrotron radiation M$"o$ssbauer spectroscopy of GdFe$$_{2}$$Hx under ultra high pressure conditions

Mitsui, Takaya; Masuda, Ryo; Seto, Makoto; Hirao, Naohisa*; Matsuoka, Takahiro*

no journal, , 

no abstracts in English

Oral presentation

2 step magnetic phase transitions of RFe$$_{2}$$Hx under ultra high pressure conditions

Mitsui, Takaya; Masuda, Ryo; Hirao, Naohisa*; Matsuoka, Takehiro*

no journal, , 

no abstracts in English

Oral presentation

Structural and valence changes of europium hydride induced by application of high-pressure H$$_{2}$$

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$$_{x}$$ exposed to high-pressure H$$_{2}$$ conditions has been studied by X-ray diffraction and M$"o$ssbauer spectroscopy measurements up to 50 GPa using synchrotron radiation. We report new structural and valence transitions, Pnma(x=2, divalent) $$rightarrow$$ P63/mmc(x=2, 7.2-8.7GPa) $$rightarrow$$ I4/m(x$$>$$2, 8.7-9.7 GPa) $$rightarrow$$ I4/mmm(x$$>$$2, 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 $$beta$$-phase of all other trivalent rare-earth metal hydrides. Our study clearly demonstrates the first observation of $$beta$$-phase of EuH$$_{x}$$ and suggest that the material is no longer an irregular member of the rare earth metal hydrides RH$$_{x}$$ systems.

Oral presentation

Polarization dependent synchrotron M$"o$ssbauer spectroscopy with diamond phase retarder and nuclear Bragg monochromator

Mitsui, Takaya; Imai, Yasuhiko*; Seto, Makoto*; Hirao, Naohisa*; Matsuoka, Takehiro*; Mibu, Ko*

no journal, , 

no abstracts in English

Oral presentation

Synchrotron M$"o$ssbauer spectroscopy of GdFe$$_{2}$$ trihydride

Mitsui, Takaya; Seto, Makoto; Masuda, Ryo*; Hirao, Naohisa*

no journal, , 

no abstracts in English

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