Neutron scattering study of antiferromagnet UPtAl

Ota, Kyugo*; Matsumoto, Yuji*; Watabe, Yuki*; Kaneko, Koji; Tabata, Chihiro; Haga, Yoshinori

New Physics; Sae Mulli, 73(12), p.1170 - 1173, 2023/12

https://doi.org/10.3938/NPSM.73.1170

We have performed the neutron scattering study of antiferromagnet UPtAl with the honeycomb lattice to determine the magnetic structure. UPtAl exhibits two phase transitions at = 9 K and = 26 K. In phase I at , the magnetic reflections described by a propagation vector = (1/3, 0, 0) were observed. In phase II at , magnetic reflections of = (1/3, 0, 0) and = (1/2, 0, 0) were observed and the magnetic reflection intensity of = (1/3, 0, 0) is weak but finite. The hysteresis in the temperature dependent intensities is observed across the phase transition at , suggesting that the transition at is of first order.

Crystallographic and/or magnetic properties of neutral and cationic uranium(IV) sandwiched phthalocyanine complexes

Tabata, Chihiro; Watanabe, Hirohito*; Shirasaki, Kenji*; Sunaga, Ayaki*; Fukuda, Takamitsu*; Li, D.*; Yamamura, Tomoo*

Journal of Molecular Structure, 1277, p.134870_1 - 134870_8, 2023/04

https://doi.org/10.1016/j.molstruc.2022.134870

Neutral and cationic U(IV) sandwiched phthalocyanine (Pc) complexes were prepared. The neutral species, UPc, was obtained by the reaction of UCl] and phthalonitrile, and the [UPc][BF] crystals were grown by electrolysis. The structures of the complexes were determined crystallographically. A U(IV) ion has two electrons, which carry a magnetic moment localized at the U sites, making the complex magnetically active. The magnetic susceptibility measurement of UPc revealed that the system was paramagnetic with local magnetic moments down to 2 K, but these magnetic moments were suppressed, possibly by a ligand field effect. The paramagnetism was also confirmed by the magnetization curve without hysteresis. The cationic complex, [UPc][BF]] crystalized in a tetragonal structure with the space group , in which the UPc molecules stacked along the tetragonal -axis. The structure was similar to that of [LnPc][BF]], but with distinct disorder in the stacking plane. The stabilities of the crystal and molecular structures and the electronic configurations of UPc and [UPc][BF]] were evaluated via the calculations that included the multiconfigurational nature of the actinide element.

Homogeneity of (U, )O ( = Th, Np) prepared by supercritical hydrothermal synthesis

Shirasaki, Kenji*; Tabata, Chihiro*; Sunaga, Ayaki*; Sakai, Hironori; Li, D.*; Konaka, Mariko*; Yamamura, Tomoo*

Journal of Nuclear Materials, 563, p.153608_1 - 153608_11, 2022/05

https://doi.org/10.1016/j.jnucmat.2022.153608

We focused on the direct synthesis of (U, )O solid solution (=Th, Np) by extending our recent progress in hydrothermal synthesis with additives. The homogeneity of the (U, )O ( = Th, Np) systems prepared by supercritical hydrothermal reactions was investigated through crystallographic analysis based on Vegard's law, and the Na nuclear magnetic resonance (NMR) measurement of (U, Np, Na)O solid solutions. Our experimental and analytical results revealed that (i) an optimal additive is ammonium carbonate and starting uranium valence is IV in the case of (U, Th)O, and (ii) an optimal additive is ethanol and starting uranium valence is VI in the case of (U, Np)O, for producing the homogeneous solid solutions by hydrothermal synthesis.

Magnetic field induced triple- magnetic order in trillium lattice antiferromagnet EuPtSi studied by resonant X-ray scattering

Tabata, Chihiro*; Matsumura, Takeshi*; Nakao, Hironori*; Michimura, Shinji*; Kakihana, Masashi*; Inami, Toshiya*; Kaneko, Koji; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Journal of the Physical Society of Japan, 88(9), p.093704_1 - 093704_5, 2019/09

https://doi.org/10.7566/JPSJ.88.093704

Thermal hydraulic analysis of the JMTR improved LEU-core

Tabata, Toshio; Nagao, Yoshiharu; Komukai, Bunsaku; Naka, Michihiro; Takeda, Takashi*; Fujiki, Kazuo

JAERI-Tech 2002-100, 108 Pages, 2003/01

JAERI-Tech-2002-100.pdf:4.44MB

After the investigation of the new core arrangement for the JMTR reactor in order to enhance the fuel burn-up and consequently extend the operation period, the "improved LEU core" that utilized 2 additional fuel elements instead of formerly installed reflector elements, was adopted. This report describes the results of the thermal-hydraulic analysis of the improved LEU core as a part of safety analysis for the licensing. The analysis covers steady state, abnormal operational transients and accidents, which were described in the annexes of the licensing documents as design bases events. Calculation conditions for the computer codes were conservatively determined based on the neutronic analysis results and others. The results of the analysis, that revealed the safety criteria were satisfied on the fuel temperature, DNBR and primary coolant temperature, were used in the licensing. The operation license of the JMTR with the improved LEU core was granted in March 2001, and the reactor operation with new core started in November 2001 as 142nd operation cycle.

Feasibility study for improvement of efficient irradiation with LEU core in JMTR

Naka, Michihiro; Nagao, Yoshiharu; Komukai, Bunsaku; Tabata, Toshio

Proceedings of 7th Meeting of the International Group on Research Reactors (IGORR-7) (CD-ROM), 7 Pages, 1999/10

no abstracts in English

Neutron scattering study on A phase and its anisotropy in EuPtSi

Kaneko, Koji; Tabata, Chihiro*; Oishi, Kazuki*; Ito, Takashi; Nakao, Hironori*; Frontzek, M. D.*; Matsuda, Masaaki*; Munakata, Koji*; Nakao, Akiko*; Ohara, Takashi; et al.

no journal, , 

no abstracts in English

Magnetic order in honeycomb layered UPtGa studied by resonant X-ray scattering

Tabata, Chihiro; Kon, Fusako*; Murata, Ryoya*; Amitsuka, Hiroshi*; Nakao, Hironori*; Matsumoto, Yuji*; Kaneko, Koji; Haga, Yoshinori

no journal, , 

Resonant X-ray scattering study of 5f-electron orderings in uranium intermetallics

Tabata, Chihiro

no journal, , 

Synchrotron X-ray and neutron diffraction studies on asymmetric quantum materials

Tabata, Chihiro

no journal, , 

no abstracts in English