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Journal Articles

$$q$$=0 long-range magnetic order in centennialite CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O; A Spin-$$frac{1}{2}$$ perfect kagome antiferromagnet with $$J_{1}$$-$$J_{2}$$-$$J_{d}$$

Iida, Kazuki*; Yoshida, Hiroyuki*; Nakao, Akiko*; Jeschke, H. O.*; Iqbal, Y.*; Nakajima, Kenji; Kawamura, Seiko; Munakata, Koji*; Inamura, Yasuhiro; Murai, Naoki; et al.

Physical Review B, 101(22), p.220408_1 - 220408_6, 2020/06

 Times Cited Count:6 Percentile:75.71(Materials Science, Multidisciplinary)

Crystal and magnetic structures of the mineral centennialite CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O are investigated by means of synchrotron X-ray diffraction and neutron diffraction measurements complemented by density functional theory (DFT) and pseudofermion functional renormalization group (PFFRG) calculations. In CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O, Cu$$^{2+}$$ ions form a geometrically perfect kagome network with antiferromagnetic $$J_{1}$$. No intersite disorder between Cu$$^{2+}$$ and Ca$$^{2+}$$ ions is detected. CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O enters a magnetic long-range ordered state below $$T_{rm N}$$ = 7.2 K, and the $$q$$=0 magnetic structure with negative vector spin chirality is obtained. The ordered moment at 0.3 K is suppressed to 0.58(2)$$mu$$B. Our DFT calculations indicate the presence of antiferromagnetic $$J_{2}$$ and ferromagnetic $$J_{d}$$ superexchange couplings of a strength which places the system at the crossroads of three magnetic orders (at the classical level) and a spin-$$frac{1}{2}$$ PFFRG analysis shows a dominance of $$q$$=0 type magnetic correlations, consistent with and indicating proximity to the observed $$q$$=0 spin structure. The results suggest that this material is located close to a quantum critical point and is a good realization of a $$J_{1}$$-$$J_{2}$$-$$J_{d}$$ kagome antiferromagnet.

Journal Articles

Neutron scattering study of yttrium iron garnet

Shamoto, Shinichi; Ito, Takashi; Onishi, Hiroaki; Yamauchi, Hiroki; Inamura, Yasuhiro; Matsuura, Masato*; Akatsu, Mitsuhiro*; Kodama, Katsuaki; Nakao, Akiko*; Moyoshi, Taketo*; et al.

Physical Review B, 97(5), p.054429_1 - 054429_9, 2018/02

 Times Cited Count:10 Percentile:63.24(Materials Science, Multidisciplinary)

Nuclear and magnetic structure and full magnon dispersions of yttrium iron garnet Y$$_3$$Fe$$_5$$O$$_{12}$$ have been studied by neutron scattering. The lowest-energy dispersion below 14 meV exhibits a quadratic dispersion as expected from ferromagnetic magnons. The imaginary part of $$q$$-integrated dynamical spin susceptibility $$chi$$"($$E$$) exhibits a square-root energy-dependence in the low energies. The magnon density of state is estimated from the $$chi$$"($$E$$) obtained on an absolute scale. The value is consistent with a single chirality mode for the magnon branch expected theoretically.

Journal Articles

Development of evaluation method for hydraulic behavior in venturi scrubber for filtered venting

Horiguchi, Naoki; Yoshida, Hiroyuki; Nakao, Yasuhiro*; Kaneko, Akiko*; Abe, Yutaka*

Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 7 Pages, 2016/11

Journal Articles

Observation of all-in type tetrahedral displacements in nonmagnetic pyrochlore niobates

Torigoe, Shuhei*; Ishimoto, Yutaro*; Aoishi, Yuhei*; Murakawa, Hiroshi*; Matsumura, Daiju; Yoshii, Kenji; Yoneda, Yasuhiro; Nishihata, Yasuo; Kodama, Katsuaki; Tomiyasu, Keisuke*; et al.

Physical Review B, 93(8), p.085109_1 - 085109_5, 2016/02

 Times Cited Count:4 Percentile:26.78(Materials Science, Multidisciplinary)

Journal Articles

Electrode properties of Li$$_{2}$$MnO$$_{3}$$ (${it C}$2/${it m}$) for a lithium-battery cathode in several charge-discharge potential ranges

Nakao, Yasuhiro*; Ozawa, Kiyoshi*; Fujii, Hiroki*; Mochiku, Takashi*; Iwai, Hideo*; Tsuchiya, Yoshinori*; Igawa, Naoki

Transactions of the Materials Research Society of Japan, 38(2), p.229 - 233, 2013/12

Li$$_{2}$$MnO$$_{3}$$ powder with a monoclinic cell related to the space group of ${it C}$2/${it m}$ was synthesized by a simplified coprecipitation method. Its electrode properties as a lithium-battery cathode were investigated in the charge-discharge potential ranges of 2.0 - 4.6, 2.0 - 4.8, and 2.0 - 5.0 V. In all the potential ranges, the electrochemical capacities gradually increased during cycling, and the increased capacities significantly depended on the potential ranges. Compared to the discharge capacities for the potential ranges of 2.0 - 4.6 and 2.0 - 5.0 V, the former merely increased from 12.5 to 22.5 mAhg$$^{-1}$$ between the 1st and 99th cycles, whereas the latter increased from 20.0 to 110.2 mAhg$$^{-1}$$ during the same cycling. The structural variation in Li$$_{2}$$MnO$$_{3}$$ is induced by the cycling, the rhombohedral phase is detected during cycling in the potential range of 2.0 - 5.0 V.

Journal Articles

Electrochemical characteristics of layered Li$$_{1.95}$$Mn$$_{0.9}$$Co$$_{0.15}$$O$$_{3}$$ (${it C}$2/${it m}$) as a lithium-battery cathode

Ozawa, Kiyoshi*; Nakao, Yasuhiro*; Mochiku, Takashi*; Cheng, Z.*; Wang, L.*; Iwai, Hideo*; Tsuchiya, Yoshinori*; Fujii, Hiroki*; Igawa, Naoki

Journal of the Electrochemical Society, 159(3), p.A300 - A304, 2012/01

 Times Cited Count:13 Percentile:49.71(Electrochemistry)

A manganese-based solid solution with the composition of Li$$_{1.95}$$Mn$$_{0.9}$$Co$$_{0.15}$$O$$_{3}$$ was synthesized by a simplified coprecipitation method, and its electrochemical characteristics as a lithium-battery cathode were investigated. Rietveld refinement based on neutron diffraction data revealed that the material is assigned to an Li$$_{2}$$MnO$$_{3}$$-type structure model with a space group symmetry of ${it C}$2/${it m}$. In cycling of the cell in the potential range from 2.0 to 4.8 V at current densities of 30 mAhg$$^{-1}$$, the discharge capacity characteristically increases from 46.3 to 196.5 mAhg$$^{-1}$$ as the cycle increases from 1 to 11, and a discharge capacity above 175.5 mAhg$$^{-1}$$ is obtained between the 23rd and 58th cycles. The cyclic voltammogram and X-ray photoelectron spectroscopy measurements showed that the manganese redox reaction is progressively activated during the first ten-odd cycles.

Journal Articles

Coherent X-ray diffraction for domain observation

Owada, Kenji; Namikawa, Kazumichi; Mizuki, Junichiro; Shimomura, Susumu*; Nakao, Hironori*; Ito, Kazuki*; Matsushita, Mitsuyoshi*; Yoneda, Yasuhiro; Murakami, Yoichi*; Hirota, Kazuma*

Transactions of the Materials Research Society of Japan, 32(1), p.7 - 10, 2007/03

An X-ray speckle pattern well reflects a particle or domain alignment on the inside of materials. Detecting the alignment is important for understanding a function of the materials such as ferroelectric, piezoelectric materials, photonic crystals and so on. We have thus constructed the apparatus for coherent X-ray diffraction at BL22XU@SPring-8, high quality slits for obtaining the full coherent X-ray beam, high resolution X-ray CCD camera for obtaining the well-resolved speckle pattern, and so on. By using the devices, we have successfully observed the speckle pattern from Cu$$_{3}$$Au, the ferroelectric material PZN-9%PT (91%Pb(Zn$$_{1/3}$$Nb$$_{2/3}$$)O$$_{3}$$-9%PbTiO$$_{3}$$) and Sr-doped BaTiO$$_{3}$$. The 2DFFT image gives us a spatial autocorrelation function which includes the information of the arrangement of the domains in the crystal within micrometers scale.

Oral presentation

Current status of an extreme environment single crystal neutron diffractometer SENJU at J-PARC

Ohara, Takashi; Kiyanagi, Ryoji; Kaneko, Koji; Tamura, Itaru; Nakao, Akiko*; Hanashima, Takayasu*; Munakata, Koji*; Moyoshi, Taketo*; Kuroda, Tetsuya*; Oikawa, Kenichi; et al.

no journal, , 

Oral presentation

Current status of extreme environment single crystal neutron diffractometer SENJU, and latest news from JRR-3

Kaneko, Koji; Ohara, Takashi; Kiyanagi, Ryoji; Kawasaki, Takuro; Oikawa, Kenichi; Tamura, Itaru; Yamauchi, Yasuhiro; Hanashima, Takayasu*; Moyoshi, Taketo*; Nakao, Akiko*; et al.

no journal, , 

Oral presentation

Current status of a TOF-Laue single crystal neutron diffractometer SENJU

Ohara, Takashi; Kiyanagi, Ryoji; Nakao, Akiko*; Hanashima, Takayasu*; Munakata, Koji*; Moyoshi, Taketo*; Kuroda, Tetsuya*; Kaneko, Koji; Tamura, Itaru; Oikawa, Kenichi; et al.

no journal, , 

Oral presentation

Applicability on two-phase flow simulation codes for Venturi scrubber

Horiguchi, Naoki; Yoshida, Hiroyuki; Nakao, Yasuhiro*; Kanagawa, Tetsuya*; Kaneko, Akiko*; Abe, Yutaka*

no journal, , 

no abstracts in English

Oral presentation

Evaluation for amount of droplets and liquid film in Venturi scrubber

Nakao, Yasuhiro*; Yoshida, Hiroyuki; Horiguchi, Naoki; Kaneko, Akiko*; Abe, Yutaka*

no journal, , 

no abstracts in English

Oral presentation

Development of evaluation method for two-phase flow in venturi scrubber for filtered venting, 2; Measurement with visualization of cross-sectional distribution of droplets

Horiguchi, Naoki; Yoshida, Hiroyuki; Nakao, Yasuhiro*; Kanagawa, Tetsuya*; Kaneko, Akiko*; Abe, Yutaka*

no journal, , 

no abstracts in English

Oral presentation

Development of evaluation method for two-phase flow in Venturi scrubber for filtered venting, 1; Measurement of liquid film thickness in diffuser part

Nakao, Yasuhiro*; Horiguchi, Naoki; Yoshida, Hiroyuki; Kanagawa, Tetsuya*; Kaneko, Akiko*; Abe, Yutaka*

no journal, , 

no abstracts in English

Oral presentation

Development of evaluation method for two-phase flow in venturi scrubber for filtered venting, 4; Visualization of droplets generation on film flow in diffuser

Horiguchi, Naoki; Yoshida, Hiroyuki; Nakao, Yasuhiro*; Kanagawa, Tetsuya*; Kaneko, Akiko*; Abe, Yutaka*

no journal, , 

no abstracts in English

Oral presentation

Development of evaluation method for two-phase flow in venturi scrubber for filtered venting, 5; Mechanism of droplet generation in annular dispersed flow

Horiguchi, Naoki; Yoshida, Hiroyuki; Nakao, Yasuhiro*; Kaneko, Akiko*; Abe, Yutaka*

no journal, , 

no abstracts in English

Oral presentation

Magnon density of states and the dispersions of Y$$_{3}$$Fe$$_{5}$$O$$_{12}$$

Shamoto, Shinichi; Ito, Takashi; Onishi, Hiroaki; Mori, Michiyasu; Matsuura, Masato*; Akatsu, Mitsuhiro*; Nakamura, Mitsutaka; Inamura, Yasuhiro; Yamauchi, Hiroki; Nakao, Akiko*; et al.

no journal, , 

no abstracts in English

17 (Records 1-17 displayed on this page)
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