Ferrimagnetic structure in the high-pressure phase of -Mn

Araki, Shingo*; Iwamoto, Kaisei*; Akiba, Kazuto*; Kobayashi, Tatsuo*; Munakata, Koji*; Kaneko, Koji; Osakabe, Toyotaka

Physical Review B, 110(9), p.094420_1 - 094420_7, 2024/09

https://doi.org/10.1103/PhysRevB.110.094420

The -Mn phase exhibits a large anomalous Hall effect (AHE) in its pressure-induced weak ferromagnetic (WFM) state, despite its relatively small spontaneous magnetization of 0.02 /Mn. To understand the underlying mechanism behind this AHE, we performed single crystal neutron diffraction measurements at 2.0 GPa to determine the magnetic structure of the WFM phase. Our investigation reveals a ferrimagnetic structure characterized by nearly collinear magnetic moments aligned along the [001] direction at sites I, II, III-1, and IV-1. In contrast, the small moments at sites III-2 and IV-2 lie within the (001) plane. The calculated net magnetization of this magnetic structure, (-0.0200.005)/Mn atom, is in excellent agreement with the experimentally determined spontaneous magnetization. The observation of a magnetic reflection at = (0, 0, 0) satisfies a key condition for the emergence of the AHE.

Activity report of the task group of radiation protection about wastes containing natural radioactive nuclides

Saito, Tatsuo; Kobayashi, Shinichi*; Zaitsu, Tomohisa*; Shimo, Michikuni*; Fumoto, Hiromichi*

Hoken Butsuri (Internet), 55(2), p.86 - 91, 2020/06

https://doi.org/10.5453/jhps.55.86

Safety cases for disposal of uranium bearing waste and NORM with uranium has not yet been fully developed in Japan, because of safety assessment of extraordinary long timespan and uncertainty in unexpected incidents with uncompleted radon impact evaluation measures arising from uranium waste disposal facility in far future. Our task group of radiation protection for wastes with natural radioactive nuclides studied some safety cases with disposal of uranium bearing waste and NORM in terms of nuclides, U-235, U-238 and their progenies, and comprehensively discussed the current state of their disposal in comparison to the ideas of international organizations such as ICRP and IAEA. We developed our ideas for long term uncertainty and radon with the knowledge of experts in each related area of direction, repeating discussions, focusing out the orientation of each directions, and outlined the recommendations with our suggestions of solving important issues in the future to be addressed.

Pressure-temperature-field phase diagram in the ferromagnet UP

Araki, Shingo*; Hayashida, Minami*; Nishiumi, Naoto*; Manabe, Hiroki*; Ikeda, Yoichi*; Kobayashi, Tatsuo*; Murata, Keizo*; Inada, Yoshihiko*; Winiewski, P.*; Aoki, Dai*; et al.

Journal of the Physical Society of Japan, 84(2), p.024705_1 - 024705_8, 2015/02

https://doi.org/10.7566/JPSJ.84.024705

Metamagnetic transition of itinerant ferromagnet UP under high pressure

Araki, Shingo*; Hayashida, Minami*; Nishiumi, Naoto*; Manabe, Hiroki*; Ikeda, Yoichi*; Kobayashi, Tatsuo*; Murata, Keizo*; Inada, Yoshihiko*; Winiewski, P.*; Aoki, Dai*; et al.

JPS Conference Proceedings (Internet), 3, p.011081_1 - 011081_6, 2014/06

https://doi.org/10.7566/JPSCP.3.011081

Demonstration of 500 keV beam acceleration on JT-60 negative-ion-based neutral beam injector

Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

http://www-naweb.iaea.org/napc/physics/FEC/FEC2010/html/node294.htm#62473

Hydrogen negative ion beams of 490keV, 3A and 510 keV, 1A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 2 m for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60 SA and ITER.

Application study on low alkaline cementitious materials for deep geological repository of high level radioactive wastes, 1; Requirements for use of cementitious materials in deep geological repository system (Joint research)

Kobayashi, Yasushi; Yamada, Tsutomu; Naito, Morimasa; Yui, Mikazu; Nakayama, Masashi; Sato, Haruo; Nishida, Takahiro*; Hironaga, Michihiko*; Yamamoto, Takeshi*; Sugiyama, Daisuke*; et al.

JAEA-Research 2008-112, 43 Pages, 2009/03

JAEA-Research-2008-112.pdf:4.58MB

In deep geological repository, use of cementitious material for rock support, lining, and grouting is essential for construction and operation and possibly raises in groundwater pH due to leachate from the cements. Since this hyperalkaline condition may lead to degradation of barriers, there is concern that it gives significant impact on long-term safety performance of the repository system. Because of these backgrounds, developments of low alkaline cement have been conducted both at home and abroad. JAEA is now planning to conduct an in-situ test for shotcreting using low alkaline cement at the Horonobe URL. On the other hand, CRIEPI has studied and developed cementitious materials for disposal of radioactive wastes. This joint research report summarizes requirements and expected performance of cementitious materials in repository taking account of surrounding conditions in each stage of the repository program so as to reflect them to further development of the low alkaline cement.

High-quality single crystal growth and physical properties in a ferromagnet UIr

Yamamoto, Etsuji; Haga, Yoshinori; Ikeda, Shugo; Matsuda, Tatsuma; Akazawa, Teruhiko*; Kotegawa, Hisashi*; Kobayashi, Tatsuo*; Onuki, Yoshichika*

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.e123 - e125, 2007/03

no abstracts in English

Change of the Fermi surface across the critical pressure in CeIn; The de Haas-van Alphen study under pressure

Settai, Rikio*; Kubo, Tetsuo*; Shiromoto, Tomoyuki*; Honda, Daisuke*; Shishido, Hiroaki*; Sugiyama, Kiyohiro*; Haga, Yoshinori; Matsuda, Tatsuma; Betsuyaku, Kiyoshi*; Harima, Hisatomo*; et al.

Journal of the Physical Society of Japan, 74(11), p.3016 - 3026, 2005/11

https://doi.org/10.1143/JPSJ.74.3016

We have studied a change of the Fermi surface in an antiferromagnet CeIn via the de Haas-van Alphen experiment under pressure up to 3 GPa. With increasing pressure P, the Neel temperature =10 K decreases and becomes zero at a critical pressure Pc 2.6 GPa. In the pressure region , we have observed a large main Fermi surface named a, which indicates that the electronic state of 4 f electron in CeIn changes from localized to itinerant at Pc, as observed in the similar antiferromagnets CeRhSi and CeRhIn. The cyclotron effective mass of this main Fermi surface is extremely enhanced around Pc: 60 at 2.7 GPa for the magnetic field along the 100 direction.

Magnetism of uranium dioxide UO under high pressure

Sakai, Hironori; Kato, Harukazu; Tokunaga, Yo; Kambe, Shinsaku; Walstedt, R. E.; Nakamura, Akio; Tateiwa, Naoyuki*; Kobayashi, Tatsuo*

Journal of Magnetism and Magnetic Materials, 272-276(Suppl.), p.e413 - e414, 2004/05

https://doi.org/10.1016/j.jmmm.2003.11.307

The d.c. magnetization of insulating UO under high pressure up to about 1 GPa has been measured using a piston-cylinder cell. Pressure-induced weak ferromagnetism was found to appear at low pressure (about 0.2 GPa). Both the remanent magnetization and the coercive force increase as pressure increases. This weak ferromagnetism may come from spin canting or from uncompensated moments around grain boundaries.

Power distributions in the High Temperature Engineering Test Reactor (HTTR) by measuring gross gamma ray from the fuel assemblies

Nojiri, Naoki; Shimakawa, Satoshi; Takamatsu, Kuniyoshi; Ishii, Yoshiki; Kawano, Shuichi; Kobayashi, Shoichi; Kawamoto, Taiki; Iyoku, Tatsuo

JAERI-Tech 2003-086, 136 Pages, 2003/11

JAERI-Tech-2003-086.pdf:8.67MB

To provide a basis for determination of the actual core power distribution, The power distribution experiments by measuring gross gamma ray emitted from fission products in the fuel assemblies were performed. The fuel assemblies were not spent condition but in-service condition. The averaged burn up was about 4,400 MWD/t. The gamma ray of a fuel assembly was measured with a GM counter under a temporary fuel withdrawing situation from the core during shutdown state. Uncertainties of the determination were from 3 to 6 percent in axial distribution per one fuel compact and within about 4 percent in radial and axial distribution of the core per one fuel assembly. It was concluded that the power distribution of the HTTR is almost equivalent to the expected power-profile shaping. Calculation of gamma ray distribution was performed by ORIGEN-2 code based the power distribution obtained by the Monte Carlo MVP code. The calculation results show good agreement with the experimental ones. The method, procedure, analysis, correction, determination and comparison are described in this report.