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Journal Articles

Superconducting spin reorientation in spin-triplet multiple superconducting phases of UTe$$_2$$

Kinjo, Katsuki*; Fujibayashi, Hiroki*; Matsumura, Hiroki*; Hori, Fumiya*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; et al.

Science Advances (Internet), 9(30), p.2736_1 - 2736_6, 2023/07

Journal Articles

Low-temperature magnetic fluctuations investigated by $$^{125}$$Te-NMR on the uranium-based superconductor UTe$$_2$$

Fujibayashi, Hiroki*; Kinjo, Katsuki*; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; et al.

Journal of the Physical Society of Japan, 92(5), p.053702_1 - 053702_5, 2023/05

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

Journal Articles

Large reduction in the $$a$$-axis knight shift on UTe$$_2$$ with $$T_c$$ = 2.1 K

Matsumura, Hiroki*; Fujibayashi, Hiroki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; et al.

Journal of the Physical Society of Japan, 92(6), p.063701_1 - 063701_5, 2023/05

Journal Articles

High-sensitive XANES analysis at Ce L$$_{2}$$-edge for Ce in bauxites using transition-edge sensors; Implications for Ti-rich geological samples

Li, W.*; Yamada, Shinya*; Hashimoto, Tadashi; Okumura, Takuma*; Hayakawa, Ryota*; Nitta, Kiyofumi*; Sekizawa, Oki*; Suga, Hiroki*; Uruga, Tomoya*; Ichinohe, Yuto*; et al.

Analytica Chimica Acta, 1240, p.340755_1 - 340755_9, 2023/02

 Times Cited Count:1 Percentile:34.31(Chemistry, Analytical)

no abstracts in English

Journal Articles

New measurement system based on small-angle neutron scattering for structural analysis of light-responsive materials

Iwase, Hiroki*; Akamatsu, Masaaki*; Inamura, Yasuhiro; Sakaguchi, Yoshifumi*; Morikawa, Toshiaki*; Kasai, Satoshi*; Ouchi, Keiichi*; Kobayashi, Kazuki*; Sakai, Hideki*

Journal of Applied Crystallography, 56(1), p.110 - 115, 2023/02

With the increasing importance of light-responsive materials, it is vital to analyze the relationship between function and structural changes induced by light irradiation. Small-angle scattering (SAS) is effective for such structural analysis. However, quantitatively capturing local molecular structure formation and molecular reactions at a scale of less than 1 nm via SAS is difficult. In this study, to analyze the structure of non-equilibrium phenomena in light-responsive materials, a new sample environment has been developed for a time-of-flight small- and wide-angle neutron scattering instrument (TAIKAN), comprising a UV-Vis irradiation system, UV-Vis absorption measurement equipment and photodetector. Simultaneous measurement of small-angle neutron scattering and UV-Vis absorption was achieved. This system was used to demonstrate the in situ observation of UV-Vis irradiation-induced structural change of micelles formed by a light-responsive surfactant sample in an aqueous solution.

Journal Articles

Change of superconducting character in UTe$$_{2}$$ induced by magnetic field

Kinjo, Katsuki*; Fujibayashi, Hiroki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; Homma, Yoshiya*; et al.

Physical Review B, 107(6), p.L060502_1 - L060502_5, 2023/02

 Times Cited Count:2 Percentile:92.2(Materials Science, Multidisciplinary)

Journal Articles

Drastic change in magnetic anisotropy of UTe$$_2$$ under pressure revealed by $$^{125}$$Te-NMR

Kinjo, Katsuki*; Fujibayashi, Hiroki*; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Nakamura, Ai*; Shimizu, Yusei*; et al.

Physical Review B, 105(14), p.L140502_1 - L140502_5, 2022/04

 Times Cited Count:3 Percentile:69.66(Materials Science, Multidisciplinary)

Journal Articles

Slow electronic dynamics in the paramagnetic state of UTe$$_2$$

Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Haga, Yoshinori; Tokiwa, Yoshifumi; Opletal, P.; Fujibayashi, Hiroki*; Kinjo, Katsuki*; Kitagawa, Shunsaku*; Ishida, Kenji*; et al.

Journal of the Physical Society of Japan, 91(2), p.023707_1 - 023707_5, 2022/02

 Times Cited Count:11 Percentile:92.14(Physics, Multidisciplinary)

$$^{125}$$Te NMR experiments in field ($$H$$) applied along the easy magnetization axis (the $$a$$-axis) revealed slow electronic dynamics developing in the paramagnetic state of UTe$$_2$$. The observed slow fluctuations are concerned with a successive growth of long-range electronic correlations below 30$$-$$40 K, where the spin susceptibility along the hard magnetization axis (the $$b$$-axis) shows a broad maximum. The experiments also imply that tiny amounts of disorder or defects locally disturb the long-range electronic correlations and develop an inhomogeneous electronic state at low temperatures, leading to a low temperature upturn observed in the bulk-susceptibility in $$H|a$$. We suggest that UTe$$_2$$ would be located on the paramagnetic side near an electronic phase boundary, where either the magnetic or Fermi-surface instability would be the origin of the characteristic fluctuations.

Journal Articles

Star-polymer-DNA gels showing highly predictable and tunable mechanical responses

Ohira, Masashi*; Katashima, Takuya*; Naito, Mitsuru*; Aoki, Daisuke*; Yoshikawa, Yusuke*; Iwase, Hiroki*; Takata, Shinichi; Miyata, Kanjiro*; Chung, U.-I.*; Sakai, Takamasa*; et al.

Advanced Materials, 34(13), p.2108818_1 - 2108818_9, 2022/01

JAEA Reports

Annual report on the effluent control of low level liquid waste in Nuclear Fuel Cycle Engineering Laboratories FY2017

Nakano, Masanao; Fujita, Hiroki; Mizutani, Tomoko; Nagaoka, Mika; Inoue, Kazumi; Koike, Yuko; Yamada, Ryohei; Yoshii, Hideki*; Hiyama, Yoshinori*; Otani, Kazunori*; et al.

JAEA-Review 2018-028, 120 Pages, 2019/02

JAEA-Review-2018-028.pdf:2.69MB

Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and by law of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2017. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.

JAEA Reports

Annual report on the effluent control of low level liquid waste in Nuclear Fuel Cycle Engineering Laboratories FY2016

Nakano, Masanao; Fujita, Hiroki; Nagaoka, Mika; Inoue, Kazumi; Koike, Yuko; Yoshii, Hideki*; Hiyama, Yoshinori*; Otani, Kazunori*; Kikuchi, Masaaki*; Sakauchi, Nobuyuki*; et al.

JAEA-Review 2017-037, 119 Pages, 2018/03

JAEA-Review-2017-037.pdf:2.58MB

Based on the regulations (the safety regulation of Tokai Reprocessing Plant, the safety regulation of nuclear fuel material usage facilities, the radiation safety rule, the regulation about prevention from radiation hazards due to radioisotopes, which are related with the nuclear regulatory acts, the local agreement concerning with safety and environment conservation around nuclear facilities, the water pollution control law, and bylaw of Ibaraki Prefecture), the effluent control of liquid waste discharged from the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency has been performed. This report describes the effluent control results of the liquid waste in the fiscal year 2016. In this period, the concentrations and the quantities of the radioactivity in liquid waste discharged from the reprocessing plant, the plutonium fuel fabrication facilities, and the other nuclear fuel material usage facilities were much lower than the limits authorized by the above regulations.

Journal Articles

Quantum spin liquid in the kagome-lattice antiferromagnet and related systems

Nakano, Hiroki*; Sakai, Toru

Journal of Physics; Conference Series, 868, p.012006_1 - 012006_10, 2017/07

 Times Cited Count:2 Percentile:68.64

The spin gap issue of the kagome lattice antiferromagnet is investigated by the finite size scaling analysis applied for the energy spectrum of the rhombic clusters calculated by the numerical exact diagonalization. The conclusion is that the kagome lattice antiferromagnet is gapless, as well as the triangular lattice one.

Journal Articles

Novel quantum phase transition in the frustrated spin nanotube

Sakai, Toru; Nakano, Hiroki*

Physics Procedia, 75, p.369 - 375, 2015/12

 Times Cited Count:1 Percentile:46.57

The S=1/2 three-leg quantum spin tube is investigated using the numerical diagonalization. The study indicated a new quantum phase transition between the 1/3 magnetization plateau phase and the plateauless one, with respect to the spin anisotropy. The phase diagram is also presented.

Journal Articles

Exotic field induced quantum phase transition of the kagome lattice antiferromagnet

Sakai, Toru; Nakano, Hiroki*

Physics Procedia, 75, p.821 - 828, 2015/12

 Times Cited Count:0 Percentile:0.04

The magnetization process of the S=1/2 kagome-lattice antiferromagnet is investigated using the numerical diagonalization up to 42-spin clusters. The critical exponent analysis confirms the unconventional magnetization behavior around the 1/3 magnetization plateau-like anomaly; the field derivative is infinite at the low-field side, while it is zero at the high-field side. We also confirm that a magnetization jump appears at 1/3 of the saturation magnetization in distorted kagome-lattice antiferromagnets.

Journal Articles

Magnetization jump in the magnetization process of the spin-1/2 Heisenberg antiferromagnet on a distorted square-kagome lattice

Nakano, Hiroki*; Hasegawa, Yasumasa*; Sakai, Toru

Journal of the Physical Society of Japan, 84(11), p.114703_1 - 114703_6, 2015/11

 Times Cited Count:30 Percentile:82.62(Physics, Multidisciplinary)

The magnetization process of the spin-1/2 Heisenberg antiferromagnet on the distorted square-kagome lattice is investigated by the large-scale numerical diagonalization method. It is found that a novel magnetization jump appears at 1/3 of the saturation magnetization.

Journal Articles

Spin nanotubes with the ring exchange interactions

Sakai, Toru; Kasahara, Toshihiro*; Hijii, Keigo*; Ota, Hitoshi*; Nakano, Hiroki*

Synthetic Metals, 208, p.26 - 28, 2015/10

 Times Cited Count:1 Percentile:4.84(Materials Science, Multidisciplinary)

The S=1/2 three-leg spin nanotube with the ring exchange interaction at each plaquette is investigated using the numerical diagonalization of finite-size systems. The previous work suggested that the system without the ring exchange interaction has a spin excitation gap between the singlet ground state and the triplet excitation, because a spontaneous dimerization occurs in the ground state. The present study indicates that as the ring exchange increases, a quantum phase transition occurs at some critical value to another spin gap phase where the pattern of the dimerization is different from the initial one.

Journal Articles

Possible singlet-triplet transition of ESR in the kagome-lattice antiferromagnet

Sakai, Toru; Hijii, Keigo*; Okubo, Susumu*; Ota, Hitoshi*; Nakano, Hiroki*; Miyashita, Seiji*

Applied Magnetic Resonance, 46(9), p.997 - 1002, 2015/09

 Times Cited Count:1 Percentile:6.54(Physics, Atomic, Molecular & Chemical)

The S=1/2 kagome-lattice antiferromagnet is investigated by the numerical diagonalization of 18-spin finite-size cluster. The matrix elements proportional to the intensity of the singlet-triplet ESR transition are calculated in the presence of the Dzyaloshinsky-Moriya interaction. Some angle-dependent selection rules is also proposed.

Journal Articles

Magnetization process of the spin-S kagome-lattice Heisenberg antiferromagnet

Nakano, Hiroki*; Sakai, Toru

Journal of the Physical Society of Japan, 84(6), p.063705_1 - 063705_5, 2015/06

 Times Cited Count:27 Percentile:80.79(Physics, Multidisciplinary)

The magnetization process of the spin-S Heisenberg antiferromagnet on the kagome lattice is studied by the numerical-diagonalization method. Our numerical-diagonalization data for small finite-size clusters with S=1, 3/2, 2 and 5/2 suggest that a magnetization plateau appears at one-third of the height of the saturation in the magnetization process irrespective of S. We discuss the S dependences of the edge fields and the width of the plateau in comparison with recent results by real-space perturbation theory.

Journal Articles

Instability of a ferrimagnetic state of a frustrated $$S$$=1/2 Heisenberg antiferromagnet in two dimensions

Nakano, Hiroki*; Sakai, Toru

Japanese Journal of Applied Physics, 54(3), p.030305_1 - 030305_4, 2015/03

To clarify the instability of the ferrimagnetism which is the fundamental magnetism of ferrite, numerical diagonalization study for the two-dimensional $$S$$=1/2 Heisenberg antiferromagnet with frustration. We find that the ferrimagnetic ground state has the spontaneous magnetization in small frustration.

Journal Articles

Instability of a ferrimagnetic state of a frustrated S=1/2 Heisenberg antiferromagnet in two dimensions

Nakano, Hiroki*; Sakai, Toru

Japanese Journal of Applied Physics, 54(3), p.030305_1 - 030305_4, 2015/03

 Times Cited Count:10 Percentile:41.61(Physics, Applied)

To clarify the instability of the ferrimagnetism which is the fundamental magnetism of ferrite, numerical-diagonalization study is carried out for the two-dimensional S=1/2 Heisenberg antiferromagnet with frustration. We find that the ferrimagnetic ground state has the spontaneous magnetization in small frustration.

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