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Journal Articles

Quantum critical behavior of the hyperkagome magnet Mn$$_3$$CoSi

Yamauchi, Hiroki; Sari, D. P.*; Yasui, Yukio*; Sakakura, Terutoshi*; Kimura, Hiroyuki*; Nakao, Akiko*; Ohara, Takashi; Honda, Takashi*; Kodama, Katsuaki; Igawa, Naoki; et al.

Physical Review Research (Internet), 6(1), p.013144_1 - 013144_9, 2024/02

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:19 Percentile:81(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

Coexisting spin resonance and long-range magnetic order of Eu in EuRbFe$$_{4}$$As$$_{4}$$

Iida, Kazuki*; Nagai, Yuki; Ishida, Shigeyuki*; Ishikado, Motoyuki*; Murai, Naoki; Christianson, A. D.*; Yoshida, Hiroyuki*; Inamura, Yasuhiro; Nakamura, Hiroki; Nakao, Akiko*; et al.

Physical Review B, 100(1), p.014506_1 - 014506_8, 2019/07

 Times Cited Count:29 Percentile:85.61(Materials Science, Multidisciplinary)

Magnetic excitations and magnetic structure of EuRbFe$$_{4}$$As$$_{4}$$ were investigated by neutron scattering measurements.

Journal Articles

Quantum magnetisms in uniform triangular lattices Li$$_{2}$$$$A$$Mo$$_{3}$$O$$_{8}$$ ($$A$$ = In, Sc)

Iida, Kazuki*; Yoshida, Hiroyuki*; Okabe, Hirotaka*; Katayama, Naoyuki*; Ishii, Yuto*; Koda, Akihiro*; Inamura, Yasuhiro; Murai, Naoki; Ishikado, Motoyuki*; Kadono, Ryosuke*; et al.

Scientific Reports (Internet), 9(1), p.1826_1 - 1826_9, 2019/02

 Times Cited Count:8 Percentile:59.99(Multidisciplinary Sciences)

Journal Articles

Spin resonance in the new-structure-type iron-based superconductor CaKFe$$_{4}$$As$$_{4}$$

Iida, Kazuki*; Ishikado, Motoyuki*; Nagai, Yuki; Yoshida, Hiroyuki*; Christianson, A. D.*; Murai, Naoki; Kawashima, Kenji*; Yoshida, Yoshiyuki*; Eisaki, Hiroshi*; Iyo, Akira*

Journal of the Physical Society of Japan, 86(9), p.093703_1 - 093703_4, 2017/09

 Times Cited Count:23 Percentile:79.35(Physics, Multidisciplinary)

Journal Articles

Damped soft phonons and diffuse scattering in (Bi$$_{1/2}$$Na$$_{1/2}$$)TiO$$_{3}$$

Matsuura, Masato*; Iida, Hiroyuki*; Hirota, Kazuma*; Owada, Kenji; Noguchi, Yuji*; Miyayama, Masaru*

Physical Review B, 87(6), p.064109_1 - 064109_10, 2013/02

 Times Cited Count:28 Percentile:74.56(Materials Science, Multidisciplinary)

Neutron-scattering studies of (Bi$$_{1/2}$$Na$$_{1/2}$$)TiO$$_{3}$$ (BNT) have been performed to elucidate the microscopic mechanism of the broad maximum in the temperature dependence of the dielectric constant at Tm $$sim$$ 600 K and the reduction in the piezoelectric properties above the depolarization temperature, 460 $$sim$$ 480 K. We observed diffuse scattering near the $$Gamma$$ point below 700 K, which competes with the superlattice peak at the M point of the tetragonal phase but coexists with the superlattice peak at the R point of the rhombohedral phase. The diffuse scattering shows an anisotropic Q shape extending along the $$<$$100$$>$$ direction transverse to the scattering vector Q, which is explained by atomic shifts bridging the tetragonal and rhombohedral structures. We propose that the broad maximum in the dielectric constant is associated with a diffusive first-order transition between the competing tetragonal and rhombohedral phases. In addition, we found that the diffuse scattering is reduced for single crystals grown under high oxygen pressure, which suggests an analogy with the central peak in hydrogen-reduced SrTiO$$_{3}$$. Inelastic neutron scattering near the $$Gamma$$ point reveals a heavily overdamped soft mode similar to those reported in lead-based relaxors, the "waterfall" feature. Moreover, a damped soft transverse acoustic mode is observed for the $$<$$100$$>$$ direction as the anisotropic diffuse scattering, indicating phase instabilities with the same origin as that of the diffuse scattering. The recovery of the soft mode is observed near the depolarization temperature, which coincides with the disappearance of the superlattice peak at the M point. These results indicate that the depolarization and the waterfall feature originate in the dynamic nature of ferroelectric clusters in the coexisting tetragonal/rhombohedral phase.

Journal Articles

Performance analysis of fusion nuclear-data benchmark experiments for light to heavy materials in MeV energy region with a neutron spectrum shifter

Murata, Isao*; Ota, Masayuki*; Miyamaru, Hiroyuki*; Kondo, Keitaro; Yoshida, Shigeo*; Iida, Toshiyuki*; Ochiai, Kentaro; Konno, Chikara

Journal of Nuclear Materials, 417(1-3), p.1127 - 1130, 2011/10

 Times Cited Count:2 Percentile:18.37(Materials Science, Multidisciplinary)

Nuclear data are indispensable for development of fusion reactor candidate materials. However, benchmarking of the nuclear data in MeV energy region is not sufficient even now. In the present study, benchmark performance in the MeV energy region was investigated theoretically in case of experiments by using a 14MeV neutron source. We carried out a systematical analysis for light to heavy materials. As a result, the benchmark performance for neutron spectrum was confirmed to be acceptable, while for $$gamma$$-ray it was not sufficient. This indicates it was effective to use a spectrum shifter. As a shifter beryllium had the best performance. Moreover, it was preliminarily examined whether it is really acceptable that only the spectrum before last collision is considered in the benchmark performance analysis. It was pointed out that not only the last collision but also more previous collisions should be taken into account equally in the benchmark performance analysis.

Journal Articles

Neutron drip line and the equation of state of nuclear matter

Oyamatsu, Kazuhiro*; Iida, Kei*; Koura, Hiroyuki

Physical Review C, 82(2), p.027301_1 - 027301_4, 2010/08

 Times Cited Count:23 Percentile:78.46(Physics, Nuclear)

We investigate how the neutron drip line is related to the density dependence of the symmetry energy, by using a macroscopic nuclear model that allows us to calculate nuclear masses in a way dependent on the equation of state of asymmetric nuclear matter. The neutron drip line obtained from these masses is shown to appreciably shift to a neutron-rich side in a nuclear chart as the density derivative of the symmetry energy increases. Such shift is clearly seen for light nuclei, a feature coming mainly from the surface property of neutron-rich nuclei.

Journal Articles

Development of CAD-to-MCNP model conversion system and its application to ITER

Sato, Satoshi; Iida, Hiromasa; Ochiai, Kentaro; Konno, Chikara; Nishitani, Takeo; Morota, Hidetsugu*; Nashif, H.*; Yamada, Masao*; Masuda, Fukuzo*; Tamamizu, Shigeyuki*; et al.

Nuclear Technology, 168(3), p.843 - 847, 2009/12

 Times Cited Count:7 Percentile:45.39(Nuclear Science & Technology)

It takes huge or unrealistic amounts of time to prepare accurate calculation inputs in shielding design for very large and complicated structure such as fusion reactors. For that reason, we have developed an automatic conversion system from three dimensional CAD drawing data into input data of the calculation geometry for a three dimensional Monte Carlo radiation transport calculation code MCNP, and applied it to an ITER benchmark model. This system consists of a void creation program (CrtVoid) for CAD drawing data and a conversion program (GEOMIT) from CAD drawing data to MCNP input data. CrtVoid creates void region data by subtracting solid region data from the whole region by Boolean operation. The void region data is very large and complicated geometry. The program divides the overall region to many small cubes, and the void region data can be created in each cube. GEOMIT generates surface data for MCNP data based on the CAD data with voids. These surface data are connected, and cell data for MCNP input data are generated. In generating cell data, additional surfaces are automatically created in the program, and undefined space and duplicate cells are removed. We applied this system to the ITER benchmark model. We successfully created void region data, and MCNP input data. We calculated neutron flux and nuclear heating. The calculation results agreed well with those with MCNP inputs generated from the same CAD data with other methods.

Journal Articles

Preliminary spectrum shifter design for intermediate energy nuclear data benchmark experiments with DT neutrons

Ota, Masayuki*; Kondo, Keitaro; Matsunaka, Masayuki*; Miyamaru, Hiroyuki*; Murata, Isao*; Iida, Toshiyuki*; Ochiai, Kentaro; Konno, Chikara

Fusion Engineering and Design, 84(7-11), p.1446 - 1449, 2009/06

 Times Cited Count:3 Percentile:24.54(Nuclear Science & Technology)

In order to validate evaluated nuclear data libraries for fusion reactor designs, various integral benchmark experiments with DT neutrons have been carried out so far on structural and advanced blanket materials at the FNS facility of JAEA. In this study, a neutron spectrum shifter, which will be placed between a sample and the DT neutron source to moderate DT neutrons incident to the sample, was adopted in order to carry out the nuclear data benchmarking induced with several MeV neutrons effectively. In order to estimate effects of the spectrum shifter, the ratio of contribution of initial 14 MeV neutrons in leakage neutron and $$gamma$$-ray spectra was calculated for the experimental configuration at FNS with a modified MCNP-4C code. The calculations were carried out for a Li$$_{2}$$TiO$$_{3}$$ sample with a Be, LiD, or D$$_{2}$$O spectrum shifter. It was found that the Be shifter was superior to others and the contribution of initial 14 MeV neutrons varied depending on material and size of the sample and shifter. The present analysis also suggested that the Be shifter was effective for secondary $$gamma$$-ray experiments.

Journal Articles

Nano-particle materials prepared from a synthetic antigenic sequence of ${it plasmodium falciparum}$ enolase

Oku, Hiroyuki*; Yamada, Keiichi*; Kobayashi, Kyoko*; Katakai, Ryoichi*; Ashfaq, M.*; Hanaoka, Hirofumi*; Iida, Yasuhiko*; Endo, Keigo*; Hasegawa, Shin; Maekawa, Yasunari; et al.

Peptide Science 2008, p.439 - 442, 2009/03

Malaria is the major cause of mortality and morbidity in the tropical and subtropical regions in the world. Our previous studies have shown that a series of partial peptides of a Plasmodium falciparum enolase have antigenic reactivity against patients' sera. In this paper, we wish to report nano-encapsulation of a synthetic antigen into bioabsorbable polymer particles and their releasing studies in vitro and in vivo.

Journal Articles

Nuclear liquid drop model revisited

Oyamatsu, Kazuhiro*; Iida, Kei*; Koura, Hiroyuki

Aichi Shukutoku Daigaku Gendai Shakai Kenkyuka Kenkyu Hokoku, (3), p.1 - 10, 2008/06

Liquid drop model is a representative model to describe binding energy and size of nuclei. This model is conventional and well reproduces bulk properties of nuclei even in current studies on nuclei. Nowadays structure of neutron-rich nuclei is paid attention to not only in nuclear physics but also in astrophysics because these nuclei play a quite important role to solve a problem of origin of elements in universe. In this paper, we investigate nuclear symmetry energy and nuclear surface energy by using the nuclear liquid drop model with some higher-order terms. The coefficients of these term are determined so as to reproduce measured nuclear masses of approximately 2200 nuclides. From this analysis, we find an indication that the fourth-order term of the symmetry energy is required and the curvature term of it is negligible. Regarding a mass-number dependency on nuclear radius, we also find that the dependency of lighter nuclei (typically with mass number, A, less than 50) is larger than that of heavier nuclei.

Journal Articles

Measurements of the depth profile of the refractive indices in oxide films on SiC by spectroscopic ellipsometry

Iida, Takeshi*; Tomioka, Yuichi*; Yoshimoto, Kimihiro*; Midorikawa, Masahiko*; Tsukada, Hiroyuki*; Orihara, Misao*; Hijikata, Yasuto*; Yaguchi, Hiroyuki*; Yoshikawa, Masahito; Ito, Hisayoshi; et al.

Japanese Journal of Applied Physics, Part 1, 41(2A), p.800 - 804, 2002/02

 Times Cited Count:15 Percentile:52.33(Physics, Applied)

no abstracts in English

Journal Articles

Characterization of the interfaces between SiC and oxide films by spectroscopic ellipsometry

Tomioka, Yuichi*; Iida, Takeshi*; Midorikawa, Masahiko*; Tsukada, Hiroyuki*; Yoshimoto, Kimihiro*; Hijikata, Yasuto*; Yaguchi, Hiroyuki*; Yoshikawa, Masahito; Ishida, Yuki*; Kosugi, Ryoji*; et al.

Materials Science Forum, 389-393, p.1029 - 1032, 2002/00

 Times Cited Count:4 Percentile:20.35(Materials Science, Multidisciplinary)

no abstracts in English

Oral presentation

Masses of unstable nuclei and the equation of state of asymmetric nuclear matter

Oyamatsu, Kazuhiro*; Iida, Kei*; Koura, Hiroyuki

no journal, , 

The symmetry energy density derivative coefficient $$L$$ in the symmetry energy of the equation of state of the nuclear matter must affect masses and radii of unstable nuclei. In the previous work we have investigated a sensitivity of $$L$$ to the nuclear radii and applied for the possibility of existence of the "pasta" nuclei in the neutron-star crust. In this work we examine a sensitivity of $$L$$ to the nuclear masses in the light nuclidic region up to nickel isotopes. We extract a macroscopic feature from the nuclear masses based on the Yamada-Matsumoto-type systematics, and try to give a value of $$L$$ determined by the experimental masses. We will discuss an ambiguity of $$L$$ in this presentation.

Oral presentation

Production of $$^{76}$$Br; labeling precursor as an PET imaging agent for a cancer diagnosis

Ishioka, Noriko; Watanabe, Shigeki; Suto, Hiroyuki*; Suzui, Nobuo; Matsuhashi, Shimpei; Iida, Yasuhiko*; Hanaoka, Hirofumi*; Yoshioka, Hiroki*; Endo, Keigo*

no journal, , 

no abstracts in English

Oral presentation

Masses of unstable nuclei and the equation of state of asymmetric nuclear matter, 2

Oyamatsu, Kazuhiro*; Iida, Kei*; Koura, Hiroyuki

no journal, , 

no abstracts in English

Oral presentation

Masses of unstable nuclei and the equation of state of asymmetric nuclear matter, 3

Oyamatsu, Kazuhiro*; Iida, Kei*; Koura, Hiroyuki

no journal, , 

no abstracts in English

Oral presentation

Nuclear liquid drop model revisited

Oyamatsu, Kazuhiro*; Iida, Kei*; Koura, Hiroyuki

no journal, , 

Liquid drop model is a representative model to describe binding energy and size of nuclei. This model is well reproduces bulk properties of nuclei even in current studies on nuclei. In this presentation, we investigate nuclear symmetry energy and nuclear surface energy by using the nuclear liquid drop model with some higher-order terms. The coefficients of these term are determined so as to reproduce measured nuclear masses of approximately 2200 nuclides. From this analysis we find an indication that the fourth-order terms of the symmetry energy is required and the curvature term of it is negligible. Regarding a mass-number dependency on nuclear radius, we also find that the dependency of lighter nuclei (typically with mass number, $$A< 50$$) is larger than that of heavier nuclei.

Oral presentation

Synthesis and evaluation of $$^{125}$$I labeled cyclic peptide, Sansalvamide A

Watanabe, Shigeki; Yamada, Keiichi*; Hanaoka, Hirofumi*; Ohshima, Yasuhiro; Tsukui, Narutaka*; Takano, Chikako*; Yamaguchi, Aiko*; Oku, Hiroyuki*; Iida, Yasuhiko*; Endo, Keigo*; et al.

no journal, , 

no abstracts in English

Oral presentation

Total reaction cross section and its effects of nuclear deformation for unstable nuclei in medium hight energy

Kohama, Akihisa*; Iida, Kei*; Oyamatsu, Kazuhiro*; Koura, Hiroyuki

no journal, , 

no abstracts in English

21 (Records 1-20 displayed on this page)