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Structural characterization and magnetic behavior of uranium compound U$$_2$$Pt$$_6$$Al$$_{15}$$

芳賀 芳範; 菅井 孝志*; 松本 裕司*; 山本 悦嗣

JPS Conference Proceedings (Internet), 29, p.013003_1 - 013003_5, 2020/02

Crystal structure and magnetic property of U$$_2$$Pt$$_6$$Al$$_{15}$$ is investigated. A single crystal X-ray diffraction experiment identified the hexagonal unit cell with a disordered structure in the uranium containing layer. A series of superstructure reflections were found. They are successfully indexed as ($$h$$/3 $$k$$/3 0), however, with a streak along the $$l$$ direction. A layered structure model containing honeycomb arrangement of uranium atoms is proposed. Preliminary magnetization measurements on a polycrystalline sample are also presented.


Weak-coupling mean-field theory of magnetic properties of NiGa$$_{2}$$S$$_{4}$$

野村 拓司*; 山本 裕史*; 吉井 賢資

Journal of the Physical Society of Japan, 89(2), p.024704_1 - 024704_10, 2020/02

 被引用回数:0 パーセンタイル:100(Physics, Multidisciplinary)

三角格子上のスピン系の磁性は物性物理の分野で古くから取り扱われている。スピン間に反強磁性的相互作用が存在する場合は、フラストレーションにより複雑な磁気状態が発生すること等から、様々な系の性質が調べられている。本系では、このような系の一つであるNiGa$$_{2}$$S$$_{4}$$の性質を平均場近似により調べた。バンド計算で求まった電子状態を基にしたHatree-Fock法により、中性子回折で観測されているインコメンシュレートなスピン秩序状態を再現することができた。Ni 3d電子間のクーロン相互作用は2eV程度と小さく、Niスピンの値もS=1.1ボーア磁子程度と小さいことから、弱相関系でありNi-Sの共有結合が強いことも判明した。スピン間の相関関数を求めたところ、中性子非弾性散乱の結果と矛盾しない結果も得られた。



佐々木 宏和*; 西久保 英郎*; 西田 真輔*; 山崎 悟志*; 中崎 竜介*; 磯松 岳己*; 湊 龍一郎*; 衣川 耕平*; 今村 明博*; 大友 晋哉*; et al.

古河電工時報, (138), p.2 - 10, 2019/02



Manifestation of electron correlation effect in 5$$f$$ states of uranium compounds revealed by 4$$d$$-5$$f$$ resonant photoelectron spectroscopy

藤森 伸一; 小畠 雅明; 竹田 幸治; 岡根 哲夫; 斎藤 祐児; 藤森 淳; 山上 浩志; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦*

Physical Review B, 99(3), p.035109_1 - 035109_5, 2019/01

 被引用回数:2 パーセンタイル:54.16(Materials Science, Multidisciplinary)

In the present study, we have elucidated the nature of the electron correlation effect in uranium compounds by imaging the partial $$mathrm{U}~5f$$ density of states (pDOS) of typical itinerant, localized, and heavy fermion uranium compounds by using the $$mathrm{U}$$ 4$$d$$-5$$f$$ resonant photoemission spectroscopy. Obtained $$mathrm{U}~5$$ pDOS exhibit a systematic trend depending on the physical properties of compounds: Although the coherent peak at the Fermi level can be explained by the band-structure calculation, an incoherent peak emerges on the higher binding energy side ($$lesssim 1~mathrm{eV}$$) in the cases of localized and heavy fermion compounds. The intensity and energy position of the incoherent peak is increased and shifted to a higher binding energy as the localization of the $$mathrm{U}~5$$ state increases. These behaviors are consistent with the prediction of the Mott metal-insulator transition, suggesting that the Hubbard-$$U$$ type mechanism takes an essential role in the $$5f$$ electronic structure of actinide materials.


Electronic structure of URu$$_2$$Si$$_2$$ studied by photoelectron spectroscopy (INVITED)

藤森 伸一; 竹田 幸治; 岡根 哲夫; 斎藤 祐児; 藤森 淳; 山上 浩志; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦*

Progress in Nuclear Science and Technology (Internet), 5, p.82 - 85, 2018/11

One of the most remarkable properties of actinide compounds is the coexistence of superconductivity and magnetic ordering which has been realized in several strongly-correlated uranium based compounds. In these compounds, both superconductivity and magnetic ordering originate from U 5f states. To understand the origin of the coexistence as well as the mechanism of the superconductivity, it is essential to reveal their U 5f electronic structures. In this presentation, the U 5f electronic structures of heavy Fermion superconductors UPd$$_2$$Al$$_3$$ and URu$$_2$$Si$$_2$$ studied by photoelectron spectroscopy using soft X-rays from SPring-8 BL23SU are presented. For UPd$$_2$$Al$$_3$$, U 4d-5f resonant photoemission experiment was performed, and its partial U 5f spectrum was revealed experimentally. Furthermore, we have applied the three-dimentional ARPES to the hidden order compound URu$$_2$$Si$$_2$$, and revealed its complete 3D electronic structure in the paramagnetic phase. Their electronic structures are discussed based on these results.


Soft X-ray magnetic circular dichroism study on UGe$$_{2}$$

竹田 幸治; 岡根 哲夫; 斎藤 祐児; 山上 浩志; 山本 悦嗣; 芳賀 芳範

Progress in Nuclear Science and Technology (Internet), 5, p.171 - 174, 2018/11

In order to investigate the electronic and magnetic states of UGe$$_{2}$$ element-specifically, we have performed soft X-ray magnetic circular dichroism experiments at the U N$$_{4,5}$$ and Ge L$$_{2,3}$$ absorption edges. We have detected the XMCD signals at both the U and Ge sites and observed clear hysteresis loops in the ferromagnetic (FM) state at T = 5.5 K. From the branching ratio B, it is found that the occupation number of 5f electrons (n$$^{5f}$$) in UGe$$_{2}$$ is close to 3. In addition, applying the magneto-optical sum rules analysis to the XMCD spectrum at the U N$$_{4,5}$$ edges, the ratio of orbital magnetic moment to the spin magnetic moment (-M$$_{L}$$/M$$_{S}$$) is estimated to be 2.17. These values of B and -M$$_{L}$$/M$$_{S}$$ are comparable compared with the results of other FM superconductors: URhGe and UCoGe


誘導結合プラズマ発光分光分析法による硝酸プルトニウム溶液中の不純物金属元素分析のための固相抽出樹脂を用いたPu, Am, Npの分離除去法の開発

田口 茂郎; 山本 昌彦; 古瀬 貴広*; 真崎 祐次*; 久野 剛彦

JAEA-Technology 2018-005, 14 Pages, 2018/06


使用済核燃料から分離回収した硝酸Pu溶液中の不純物金属(Fe, Cr, Ni, Mn, Al, Cd, V, Cu, Si, Zn, Mo, Sn, Ca, Mg, Na, Ag, Pb, B)を誘導結合プラズマ発光分光分析法(ICP-OES)により定量するにあたり、アクチニドに対して高い吸着性を有する固相抽出樹脂を用いて、硝酸Pu溶液中のPu, Am及びNpを吸着除去し、不純物金属成分と分離する手法を開発した。本手法では、TRU樹脂を充填したカラムを2段として、1段目のカラムで主にPuとAmを吸着除去し、次にNpの原子価をNp(IV)に調整した後、2段目のTRUカラムに通液し、1段目のカラムから溶出したAm(III)とNp(IV)を吸着除去した。本分離法により、東海再処理施設において分離回収された硝酸Pu溶液(22g/L)2mLを処理した結果、回収液(100mL定容後)中の全$$alpha$$放射能濃度を$$<$$5.8Bq/mLまで低減することができた。分離後の試料をICP-OESで測定した結果、測定対象の不純物金属元素を全量回収でき、本法が、硝酸Pu溶液中のICP-OESによる不純物金属分析に先立つPu, Am, Np除去のための分離前処理法として有効であることを確認した。


Element-specific observation of the ferromagnetic ordering process in UCoAl via soft X-ray magnetic circular dichroism

竹田 幸治; 斎藤 祐児; 岡根 哲夫; 山上 浩志; 松田 達磨*; 山本 悦嗣; 芳賀 芳範; 大貫 惇睦*

Physical Review B, 97(18), p.184414_1 - 184414_7, 2018/05


 被引用回数:1 パーセンタイル:100(Materials Science, Multidisciplinary)

We have performed soft X-ray magnetic circular dichroism (XMCD) experiments on the itinerant-electron metamagnet UCoAl at the U 4$$d$$-5$$f$$ ($$N_mathrm{4, 5}$$) and Co 2$$p$$-3$$d$$ ($$L_mathrm{2, 3}$$) absorption edges in order to investigate the magnetic properties of the U 5$$f$$ and Co 3$$d$$ electrons separately. From the line shape of the XMCD spectrum, it is deduced that the orbital magnetic moment of the Co 3$$d$$ electrons is unusually large. Through the systematic temperature ($$T$$)- and magnetic field ($$H$$)-dependent XMCD measurements, we have obtained two types of the magnetization curve as a function of $$H$$ and $$T$$ (M-H curve and M-T curve, respectively). The metamagnetic transition from a paramagnetic state to a field-induced ferromagnetic state was observed clearly under 15 K at $$H_mathrm{M}$$. The value of the $$H_mathrm{M}$$ and its $$T$$-dependence agree well between the U and Co sites, and the bulk magnetization. Whereas, we have discovered the remarkable differences in the M-H and M-T curves between the U and Co sites. The present findings show clearly that the role of the Co 3$$d$$ electrons should be considered more carefully in order to understand the origin of the magnetic ordering in UCoAl.


Crystallographic, magnetic, thermal, and electric transport properties in UPtIn single crystal

松本 裕司*; 芳賀 芳範; 立岩 尚之; 山本 悦嗣; Fisk, Z.*

Journal of the Physical Society of Japan, 87(2), p.024706_1 - 024706_4, 2018/02

 被引用回数:0 パーセンタイル:100(Physics, Multidisciplinary)

Single crystal samples of UPtIn with the hexagonal structure are grown from indium flux. Strong uniaxial magnetic anisotropy is revealed from magnetic property measurements. Specific heat measurement reveals a significant deviation from $$T$$-linear behavior, indicating the smaller electronic specific heat than the previous study.


Determination of fusion barrier distributions from quasielastic scattering cross sections towards superheavy nuclei synthesis

田中 泰貴*; 成清 義博*; 森田 浩介*; 藤田 訓裕*; 加治 大哉*; 森本 幸司*; 山木 さやか*; 若林 泰生*; 田中 謙伍*; 武山 美麗*; et al.

Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01

 被引用回数:7 パーセンタイル:29.57(Physics, Multidisciplinary)

ガス充填型反跳生成核分離装置GARISを用いて$$^{48}$$Ca + $$^{208}$$Pb, $$^{50}$$Ti + $$^{208}$$Pb, $$^{48}$$Ca + $$^{248}$$Cm反応系における準弾性散乱断面積の励起関数を測定した。これらのデータから融合障壁分布を導出し、チャンネル結合計算と比較した。$$^{48}$$Ca + $$^{208}$$Pb及び$$^{50}$$Ti + $$^{208}$$Pb反応の障壁分布のピークエネルギーはそれらの反応系における2中性子蒸発断面積のピークエネルギーと良く一致し、一方$$^{48}$$Ca + $$^{248}$$Cm反応の障壁分布のピークエネルギーは4中性子蒸発断面積のピークエネルギーより少し下に現れることが判った。この結果は超重核合成の際の最適ビームエネルギーの予測に役立つ情報を与える。


New precise measurement of muonium hyperfine structure interval at J-PARC

上野 恭裕*; 青木 正治*; 深尾 祥紀*; 東 芳隆*; 樋口 嵩*; 飯沼 裕美*; 池戸 豊*; 石田 啓一*; 伊藤 孝; 岩崎 雅彦*; et al.

Hyperfine Interactions, 238(1), p.14_1 - 14_6, 2017/11

 被引用回数:3 パーセンタイル:6.53

MuSEUM is an international collaboration aiming at a new precise measurement of the muonium hyperfine structure at J-PARC (Japan Proton Accelerator Research Complex). Utilizing its intense pulsed muon beam, we expect a ten-fold improvement for both measurements at high magnetic field and zero magnetic field. We have developed a sophisticated monitoring system, including a beam profile monitor to measure the 3D distribution of muonium atoms to suppress the systematic uncertainty.


Electronic structure of ThRu$$_2$$Si$$_2$$ studied by angle-resolved photoelectron spectroscopy; Elucidating the contribution of U 5$$f$$ states in URu$$_{2}$$Si$$_{2}$$

藤森 伸一; 小畠 雅明; 竹田 幸治; 岡根 哲夫; 斎藤 祐児; 藤森 淳; 山上 浩志; 松本 裕司*; 山本 悦嗣; 立岩 尚之; et al.

Physical Review B, 96(12), p.125117_1 - 125117_9, 2017/09

 被引用回数:5 パーセンタイル:55.89(Materials Science, Multidisciplinary)

The Fermi surface and band structure of $$mathrm{ThRu}_2mathrm{Si}_2$$ have been studied by angle resolved photoelectron spectroscopy (ARPES) with the incident photon energies of $$hnu$$ = 665-735 eV. Detailed band structure and the three-dimensional shape of the Fermi surface were derived experimentally, and they are quantitatively explained by the band-structure calculation based on the density functional approximation. Comparison of the experimental ARPES spectra of $$mathrm{ThRu}_2mathrm{Si}_2$$ with those of $$mathrm{URu}_2mathrm{Si}_2$$ shows that they have considerably different spectral profiles particularly in the energy range of $$E_mathrm{B} = E_mathrm{F}$$ - 1 eV. Some energy bands with their energy dispersions of about 1 eV observed in $$mathrm{URu}_2mathrm{Si}_2$$ are missing in the ARPES spectra of $$mathrm{ThRu}_2mathrm{Si}_2$$ measured along the same high symmetry line of Brillouin zone, suggesting that U 5$$f$$ states form these bands in $$mathrm{URu}_2mathrm{Si}_2$$. The relationship between the ARPES spectra of $$mathrm{URu}_2mathrm{Si}_2$$ and $$mathrm{ThRu}_2mathrm{Si}_2$$ is very different from the case between $$mathrm{CeRu}_2mathrm{Si}_2$$ and $$mathrm{LaRu}_2mathrm{Si}_2$$ where their intrinsic difference is limited only in the very vicinity of the Fermi energy. The present result argues that the U 5$$f$$ electrons in $$mathrm{URu}_2mathrm{Si}_2$$ have strong hybridization with ligand states, and essentially have an itinerant character.


Electronic structures of U$$X_3$$ ($$X$$=Al, Ga, and In) studied by photoelectron spectroscopy

藤森 伸一; 小畠 雅明; 竹田 幸治; 岡根 哲夫; 斎藤 祐児; 藤森 淳; 山上 浩志; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦*

Physical Review B, 96(11), p.115126_1 - 115126_10, 2017/09

 被引用回数:5 パーセンタイル:55.89(Materials Science, Multidisciplinary)

The electronic structures of U$$X_3$$ ($$X$$=Al, Ga, and In) were studied by photoelectron spectroscopy to understand the the relationship between their electronic structure and magnetic properties. The band structures and Fermi surfaces of UAl$$_3$$ and UGa$$_3$$ were revealed experimentally by angle-resolved photoelectron spectroscopy (ARPES), and they were compared with the result of band structure calculations. The topologies of the Fermi surfaces and the band structures of UAl$$_3$$ and UGa$$_3$$ were explained reasonably well by the calculation, although bands near the Fermi level ($$E_mathrm{F}$$) were renormalized owing to the finite electron correlation effect. The topologies of the Fermi surfaces of UAl$$_3$$ and UGa$$_3$$ are very similar to each other, except for some minor differences. Such minor differences in their Fermi surface or electron correlation effect might take an essential role in their magnetism.


Magnetoresistance and Hall effect of antiferromagnetic uranium compound URhIn$$_5$$

芳賀 芳範; 松本 裕司*; Pospisil, J.; 立岩 尚之; 山本 悦嗣; 山村 朝雄*; Fisk, Z.*

Journal of Physics; Conference Series, 807(1), p.012015_1 - 012015_4, 2017/04

 被引用回数:1 パーセンタイル:48.92

Transport characteristics of an antiferromagnetic uranium compound URhIn$$_5$$ are studied. The antiferromagnetic transition leads to a formation of a gap on the Fermi surface as demonstrated by a hump in the resistivity behavior as a function of temperature. Hall effect, magnetoresistance and de Haas-van Alphen study consistently demonstrate a small carrier concentration in the antiferromagnetic state suggesting that majority of the Fermi surface vanishes.


Metallurgical investigations on creep rupture mechanisms of dissimilar welded joints between Gr.91 and 304SS

山下 拓哉; 永江 勇二; 菊地 浩一*; 山本 賢二*

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 8 Pages, 2017/04

A dissimilar welded joint was adopted to achieve higher thermal efficiency and economy levels in nuclear and thermal power plants. 2 types of dissimilar welded joints which were different heat input during welding to the ferrite steels were manufactured. The dissimilar welded joints were made of following materials; the modified 9Cr-1Mo steel (Gr. 91) for the ferritic steels, the 304 stainless steel for the austenitic steels and the Inconel 600 for the filler metals, Welding methods for the modified 9Cr-1Mo steel were used Plasma Arc Welding and Gas Tungsten Arc Welding (GTAW), respectively. Creep tests were conducted. Specimens by GTAW failed in base metal part and interface between the modified 9Cr-1Mo steel and Inconel 600. Interface failure mechanisms were analyzed from a perspective of metallurgy which were precipitation and growth of type I carbide and formation of oxide layer.


New muonium HFS measurements at J-PARC/MUSE

Strasser, P.*; 青木 正治*; 深尾 祥紀*; 東 芳隆*; 樋口 嵩*; 飯沼 裕美*; 池戸 豊*; 石田 啓一*; 伊藤 孝; 岩崎 雅彦*; et al.

Hyperfine Interactions, 237(1), p.124_1 - 124_9, 2016/12

 被引用回数:5 パーセンタイル:6.99

At the Muon Science Facility (MUSE) of J-PARC (Japan Proton Accelerator Research Complex), the MuSEUM collaboration is planning new measurements of the ground state hyperfine structure (HFS) of muonium both at zero field and at high magnetic field. The previous measurements were performed both at LAMPF (Los Alamos Meson Physics Facility) with experimental uncertainties mostly dominated by statistical errors. The new high intensity muon beam that will soon be available at MUSE H-Line will provide an opportunity to improve the precision of these measurements by one order of magnitude. An overview of the different aspects of these new muonium HFS measurements, the current status of the preparation, and the results of a first commissioning test experiment at zero field are presented.


Fermi surface of ThRu$$_{2}$$Si$$_{2}$$ as a reference to the strongly correlated isostructural metals investigated by quantum oscillations

松本 裕司*; 芳賀 芳範; 立岩 尚之; 青木 晴善*; 木村 憲彰*; 山村 朝雄*; 山本 悦嗣; 松田 達磨*; Fisk, Z.*; 山上 浩志*

Journal of the Physical Society of Japan, 85(10), p.104709_1 - 104709_7, 2016/10

 被引用回数:2 パーセンタイル:71.46(Physics, Multidisciplinary)

dHvA oscillations were detected on an actinide compound ThRu$$_2$$Si$$_2$$ which is regarded as a reference to strongly correlated electron systems URu$$_2$$Si$$_2$$ and CeRu$$_2$$Si$$_2$$. Observed Fermi surfaces well coincides with the band structure calculations, as well as experimentally obtained ones for a heavy fermion compound CeRu$$_2$$Si$$_2$$. On the other hand, Fermi surfaces of URu$$_2$$Si$$_2$$ have significantly different characteristics, suggesting an itinerant ground state of 5f electrons.


Electronic structures of uranium compounds studied by soft X-ray photoelectron spectroscopy

藤森 伸一; 竹田 幸治; 岡根 哲夫; 斎藤 祐児; 藤森 淳; 山上 浩志; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦

Journal of the Physical Society of Japan, 85(6), p.062001_1 - 062001_33, 2016/06

 被引用回数:21 パーセンタイル:15.37(Physics, Multidisciplinary)

The electronic structures of uranium-based compounds are studied by photoelectron spectroscopies with soft X-ray synchrotron radiation. Angle-resolved photoelectron spectroscopy with soft X-rays made it possible to directly observe their bulk band structures and Fermi surfaces. It is shown that the band structure and Fermi surface of itinerant compounds are quantitatively explained by the band-structure calculation treating all U 5$$f$$ electrons as being itinerant. Furthermore, the overall electronic structures of heavy Fermion compounds are also explained by the band-structure calculation although there exist some disagreements which might be originated from the electron correlation effect. This suggests that the itinerant description of U $$5f$$ states is an appropriate starting point for their description. The local electronic structures of uranium site are probed by the core-level photoelectron spectroscopy with soft X-rays. The comparisons of core-level spectra of these compounds with typical itinerant and localized compounds suggest that the local electronic structures of most of itinerant and heavy Fermion compounds are close to U 5$$f^3$$ configuration.


Recent progress of soft X-ray photoelectron spectroscopy studies of uranium compounds

藤森 伸一; 竹田 幸治; 岡根 哲夫; 斎藤 祐児; 藤森 淳; 山上 浩志; 山本 悦嗣; 芳賀 芳範; 大貫 惇睦

Journal of Electron Spectroscopy and Related Phenomena, 208, p.105 - 110, 2016/04

 被引用回数:1 パーセンタイル:86.59(Spectroscopy)



Strength of 316FR joints welded by Type 316FR/16-8-2 filler metals

山下 拓哉; 永江 勇二; 佐藤 健一郎*; 山本 賢二*

Journal of Pressure Vessel Technology, 138(2), p.024501_1 - 024501_7, 2016/04

 被引用回数:0 パーセンタイル:100(Engineering, Mechanical)

316FR stainless steel is a candidate structural material of JSFR. Two types of weld metals are candidates for 316FR welded joints; 316FR weld metal and 16-8-2 weld metal. This study evaluated the need to consider the welded joint strength reduction factors in 316FR welded joints. To this end, the tensile and creep strengths of Type 316FR and Type 16-8-2 weld metals were measured, and the effect of delta-ferrite in weld metals was evaluated in creep-strength tests of 316FR welded joints. In tensile and creep strengths of 316FR joints welded by both metal types, the welded joint strength reduction factors were immaterial. The creep strength of 316FR welded joints was negligibly affected by delta-ferrite levels from 4.1 FN to 7.0 FN. Furthermore, the tensile and creep strengths of 316FR joints welded by two methods (Tungsten Inert Gas Welding and Shielded Metal Arc Welding) were the same.

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