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Journal Articles

Chiral Dirac fermion in a collinear antiferromagnet

Zhang, A.*; Deng, K.*; Sheng, J.*; Liu, P.*; Kumar, S.*; Shimada, Kenya*; Jiang, Z.*; Liu, Z.*; Shen, D.*; Li, J.*; et al.

Chinese Physics Letters, 40(12), p.126101_1 - 126101_8, 2023/12

Journal Articles

Incommensurate helimagnetic structure of Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ determined by single-crystal neutron diffraction

Tanaka, Seiya*; Kiyanagi, Ryoji; Ishikawa, Yoshihisa*; Amako, Yasushi*; Iiyama, Taku*; Futamura, Ryusuke*; Maruyama, Kenichi*; Utsumi, Shigenori*

Physical Review Materials (Internet), 7(1), p.014403_1 - 014403_11, 2023/01

Journal Articles

Magnetic phase diagram of helimagnetic Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ (0 $$leq$$ x $$leq$$ 0.2) hexagonal ferrite

Maruyama, Kenichi*; Tanaka, Seiya*; Kiyanagi, Ryoji; Nakao, Akiko*; Moriyama, Kentaro*; Ishikawa, Yoshihisa*; Amako, Yasushi*; Iiyama, Taku*; Futamura, Ryusuke*; Utsumi, Shigenori*; et al.

Journal of Alloys and Compounds, 892, p.162125_1 - 162125_8, 2022/02

 Times Cited Count:2 Percentile:17.65(Chemistry, Physical)

Journal Articles

Stabilization of size-controlled BaTiO$$_3$$ nanocubes via precise solvothermal crystal growth and their anomalous surface compositional reconstruction

Nakashima, Koichi*; Onagi, Kaito*; Kobayashi, Yoshio*; Ishigaki, Toru*; Ishikawa, Yoshihisa*; Yoneda, Yasuhiro; Yin, S.*; Kakihana, Masato*; Sekino, Toru*

ACS Omega (Internet), 6(14), p.9410 - 9425, 2021/04

 Times Cited Count:7 Percentile:61.28(Chemistry, Multidisciplinary)

We succeeded in synthesizing barium titanate nanocubes by hydrothermal synthesis. When the nanocubes were examined in detail using a scanning electron microscope, pulsed neutrons, and large synchrotron radiation, it was found that a reconstituted layer of titanium oxide was formed on the surface.

Journal Articles

Origin of magnetovolume effect in a cobaltite

Miao, P.*; Tan, Z.*; Lee, S. H.*; Ishikawa, Yoshihisa*; Torii, Shuki*; Yonemura, Masao*; Koda, Akihiro*; Komatsu, Kazuki*; Machida, Shinichi*; Sano, Asami; et al.

Physical Review B, 103(9), p.094302_1 - 094302_18, 2021/03

 Times Cited Count:1 Percentile:18.63(Materials Science, Multidisciplinary)

The layered perovskite PrBaCo$$_{2}$$O$$_{5.5}$$ demonstrates a strong negative thermal expansion (NTE) which holds potential for being fabricated into composites with zero thermal expansion. The NTE was found to be intimately associated with the spontaneous magnetic ordering, known as magneto-volume effect (MVE). Here we report with compelling evidences that the continuous-like MVE in PrBaCo$$_{2}$$O$$_{5.5}$$ is intrinsically of discontinuous character, originating from an magnetoelectric transition from an antiferromagnetic insulating large-volume (AFILV) phase to a ferromagnetic less-insulating small-volume (FLISV) phase. Furthermore, the magnetoelectric effect (ME) shows high sensitivity to multiple external stimuli such as temperature, carrier doping, hydrostatic pressure, magnetic field etc. In contrast to the well-known ME such as colossal magnetoresistance and multi-ferroic effect which involve symmetry breaking of crystal structure, the ME in the cobaltite is purely isostructural. Our discovery provides a new path way to realizing the ME as well as the NTE, which may find applications in new techniques.

Journal Articles

Flux growth and magnetic properties of helimagnetic hexagonal ferrite Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ single crystals

Utsumi, Shigenori*; Tanaka, Seiya*; Maruyama, Kenichi*; Amako, Yasushi*; Kiyanagi, Ryoji; Nakao, Akiko*; Moriyama, Kentaro*; Ishikawa, Yoshihisa*; 9 of others*

ACS Omega (Internet), 5(38), p.24890 - 24897, 2020/09

 Times Cited Count:4 Percentile:21.77(Chemistry, Multidisciplinary)

Fabricating large, high-crystalline-quality single-crystal samples of hexagonal ferrite Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ is the first important step to elucidating its helimagnetic structure and developing it for further applications. In this study, single crystals of Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ of various Sc concentrations $$x$$ were successfully grown by the spontaneous crystallization method using Na$$_{2}$$O-Fe$$_{2}$$O$$_{3}$$ flux. X-ray diffraction and elemental analysis revealed that the obtained crystals were composed of single-phase Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ of high crystalline quality. The temperature dependence of magnetization and the magnetization curves at 77 K of the $$x$$ = 0.128 crystal exhibited behavior characteristics of helimagnetism. Neutron diffraction measurements of the $$x$$ = 0.128 crystal exhibited magnetic satellite reflection peaks below 211K, proving evidence that Ba(Fe$$_{1-x}$$Sc$$_{x}$$)$$_{12}$$O$$_{19}$$ behaves as a helimagnetic material.

Journal Articles

Strong lattice anharmonicity exhibited by the high-energy optical phonons in thermoelectric material

Wu, P.*; Fan, F.-R.*; Hagihara, Masato*; Kofu, Maiko; Peng, K.*; Ishikawa, Yoshihisa*; Lee, S.*; Honda, Takashi*; Yonemura, Masao*; Ikeda, Kazutaka*; et al.

New Journal of Physics (Internet), 22(8), p.083083_1 - 083083_9, 2020/08

 Times Cited Count:6 Percentile:55.6(Physics, Multidisciplinary)

Thermoelectric material SnSe has aroused world-wide interests in the past years, and its inherent strong lattice anharmonicity is regarded as a crucial factor for its outstanding thermoelectric performance. However, the understanding of lattice anharmonicity in SnSe system remains inadequate, especially regarding how phonon dynamics are affected by this behavior. In this work, we present a comprehensive study of lattice dynamics on Na$$_{0.003}$$Sn$$_{0.997}$$Se$$_{0.9}$$S$$_{0.1}$$ by means of neutron total scattering, inelastic neutron scattering, Raman spectroscopy as well as frozen-phonon calculations. Lattice anharmonicity is evidenced by pair distribution function, inelastic neutron scattering and Raman measurements. By separating the effects of thermal expansion and multi-phonon scattering, we found that the latter is very significant in high-energy optical phonon modes. The strong temperature-dependence of these phonon modes indicate the anharmonicity in this system. Moreover, our data reveals that the linewidths of high-energy optical phonons become broadened with mild doping of sulfur. Our studies suggest that the thermoelectric performance of SnSe could be further enhanced by reducing the contributions of high-energy optical phonon modes to the lattice thermal conductivity via phonon engineering.

Journal Articles

Crystal structure and cation distribution of the X-type hexaferrite Sr$$_{2}$$Co$$_{2}$$Fe$$_{28}$$O$$_{46}$$

Komabuchi, Mai*; Urushihara, Daisuke*; Asaka, Toru*; Fukuda, Koichiro*; Ohara, Takashi; Munakata, Koji*; Ishikawa, Yoshihisa*

Journal of the Physical Society of Japan, 89(3), p.034601_1 - 034601_5, 2020/03

 Times Cited Count:0 Percentile:22.58(Physics, Multidisciplinary)

Journal Articles

Crystal structures of highly hole-doped layered perovskite nickelate Pr$$_{2-x}$$Sr$$_{x}$$NiO$$_{4}$$ studied by neutron diffraction

Kajimoto, Ryoichi; Nakajima, Kenji; Fujita, Masaki*; Ishikado, Motoyuki*; Torii, Shuki*; Ishikawa, Yoshihisa*; Miao, P.*; Kamiyama, Takashi*

Journal of the Physical Society of Japan, 88(11), p.114602_1 - 114602_6, 2019/11

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

Journal Articles

Quantum paramagnet near spin-state transition

Tomiyasu, Keisuke*; Ito, Naoko*; Okazaki, Ryuji*; Takahashi, Yuki*; Onodera, Mitsugi*; Iwasa, Kazuaki*; Nojima, Tsutomu*; Aoyama, Takuya*; Ogushi, Kenya*; Ishikawa, Yoshihisa*; et al.

Advanced Quantum Technologies (Internet), 1(3), p.1800057_1 - 1800057_7, 2018/12

Spin-state transition, also known as spin crossover, plays a key role in diverse systems. In theory, the boundary range between the low- and high-spin states is expected to enrich the transition and give rise to unusual physical states. However, no compound that realizes a nearly degenerate critical range as the ground state without requiring special external conditions has yet been experimentally identified. This study reports that the Sc substitution in LaCoO3 destabilizes its nonmagnetic low-spin state and generates an anomalous paramagnetic state accompanied by the enhancement of transport gap and magneto-lattice-expansion as well as the contraction of Co-O distance with the increase of electron site transfer. These phenomena are not well described by the mixture of conventional low- and high-spin states, but by their quantum superposition occurring on the verge of a spin-state transition.

Journal Articles

Investigation of the electronic structure and lattice dynamics of the thermoelectric material Na-doped SnSe

Wu, P.*; Zhang, B.*; Peng, K. L.*; Hagiwara, Masayuki*; Ishikawa, Yoshihisa*; Kofu, Maiko; Lee, S. H.*; Kumigashira, Hiroshi*; Hu, C. S.*; Qi, Z. M.*; et al.

Physical Review B, 98(9), p.094305_1 - 094305_7, 2018/09

 Times Cited Count:9 Percentile:46.45(Materials Science, Multidisciplinary)

Using angle-resolved photoemission spectroscopy and inelastic neutron scattering, we have studied how electronic structures and lattice dynamics evolve with temperature in Na-doped SnSe.

Journal Articles

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex, 2; Neutron scattering instruments

Nakajima, Kenji; Kawakita, Yukinobu; Ito, Shinichi*; Abe, Jun*; Aizawa, Kazuya; Aoki, Hiroyuki; Endo, Hitoshi*; Fujita, Masaki*; Funakoshi, Kenichi*; Gong, W.*; et al.

Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.

Journal Articles

Bipartite magnetic parent phases in the iron oxypnictide superconductor

Hiraishi, Masatoshi*; Iimura, Soshi*; Kojima, Kenji*; Yamaura, Junichi*; Hiraka, Haruhiro*; Ikeda, Kazutaka*; Miao, P.*; Ishikawa, Yoshihisa*; Torii, Shuki*; Miyazaki, Masanori*; et al.

Nature Physics, 10(4), p.300 - 303, 2014/04

 Times Cited Count:101 Percentile:95.53(Physics, Multidisciplinary)

Oral presentation

Neutron scattering study on regulated nano space compounds

Kaneko, Koji; Matsuda, Tatsuma; Ishikawa, Yoshihisa*; Kimura, Hiroyuki*; Noda, Yukio; Momma, Koichi*; Izumi, Fujio*

no journal, , 

no abstracts in English

Oral presentation

Proton conduction path in Rb$$_{3}$$H(SeO$$_{4}$$)$$_{2}$$ studied by high temperature neutron single crystal diffraction

Kiyanagi, Ryoji; Ishikawa, Yoshihisa*; Noda, Yukio*

no journal, , 

Rb$$_{3}$$H(SeO$$_{4}$$)$$_{2}$$ is known to exhibit a super protonic conductivity at rather low temperature and has attracted much attention. The protonic conductivity emerges upon a structural phase transition, thus the protonic conductivity is believed to have close relation with the crystal structure. In order to clarify the relation between the internal structure and the realization of the super protonic conductivity as well as the conduction mechanism, single crystal neutron diffraction was carried out. The results showed that the hydrogen-bond length monotonically increases as the temperature increases and no peculiar behavior in the internal structure has been recognized. The structure analysis in the proton-conducting phase revealed that the hydrogen atoms (protons) migrate over the equivalent sites via intermediate sites.

Oral presentation

Proton conduction mechanism and phase transition of (Rb,K)$$_{3}$$H(SeO$$_{4}$$)$$_{2}$$

Kiyanagi, Ryoji; Matsuo, Yasumitsu*; Ishikawa, Yoshihisa*; Noda, Yukio*; Ohara, Takashi; Kawasaki, Takuro; Oikawa, Kenichi; Kaneko, Koji; Tamura, Itaru; Hanashima, Takayasu*; et al.

no journal, , 

The materials represented as M$$_{3}$$H(XO$$_{4}$$)$$_{2}$$ (M=alkali metals, X=Se, S) are known to exhibit high protonic conductivities at relatively low temperature. Although the high protonic conductivity is considered to be due to the disorder of the hydrogen bonds in the materials, details have not been well understood. In addition, clarification of the phase transition to the high proton conducting phase is important in order to understand the realization of the high protonic conductivity. In this study, a high temperature neutron structural study was carried out on Rb$$_{3}$$H(SeO$$_{4}$$)$$_{2}$$, and the solid solution of Rb$$_{3-x}$$K$$_{x}$$H(SeO$$_{4}$$)$$_{2}$$ were also investigated by means of conductivity measurements and neutron structural studies. The high temperature neutron structure analyses revealed that the protons in the high proton conducting phase were two dimensionally distributed, which is considered to be the direct observation of the conducting protons. The solid solution exhibited non-linear decreases of the phase transition temperatures as the K concentration increased. The K ions were found to prefer to occupy one of two possible sites, of which occupancies apparently have close relationship with the phase transition temperature.

Oral presentation

The Latest status of a TOF single crystal neutron diffractometer SENJU at J-PARC

Ohara, Takashi; Kiyanagi, Ryoji; Nakao, Akiko*; Munakata, Koji*; Ishikawa, Yoshihisa*; Moriyama, Kentaro*; Tamura, Itaru; Kaneko, Koji

no journal, , 

Oral presentation

Quantitative analysis of heavy neutron absorbing material at SENJU

Kiyanagi, Ryoji; Ishikawa, Yoshihisa*; Ohara, Takashi; Moriyama, Kentaro*; Munakata, Koji*; Nakao, Akiko*; Sakakura, Terutoshi*; Kimura, Hiroyuki*

no journal, , 

SENJU is a single crystal neutron diffractometer at Material and Life science experimental Facility (MLF) in J-PARC. In this study, a heavy neutron absorbing material has been measured in order to evaluate the feasibility of qualitative structure analyses on such material. The result showed that with some tricks in the measurement and treatment on the measured data, quantitative structure analyses has been demonstrated to be feasible.

Oral presentation

The Latest status of a TOF single crystal neutron diffractometer SENJU at J-PARC

Ohara, Takashi; Kiyanagi, Ryoji; Nakao, Akiko*; Munakata, Koji*; Ishikawa, Yoshihisa*; Moriyama, Kentaro*; Tamura, Itaru; Kaneko, Koji

no journal, , 

Oral presentation

Crystal structures of highly hole-doped Pr$$_{2-x}$$Sr$$_{x}$$NiO$$_{4}$$ studied by high-resolution neutron diffraction

Kajimoto, Ryoichi; Nakajima, Kenji; Fujita, Masaki*; Ishikado, Motoyuki*; Torii, Shuki*; Ishikawa, Yoshihisa*; Miao, P.*; Kamiyama, Takashi*

no journal, , 

no abstracts in English

33 (Records 1-20 displayed on this page)