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Electronic structure of UTe$$_2$$ studied by photoelectron spectroscopy

藤森 伸一; 川崎 郁斗; 竹田 幸治; 山上 浩志; 仲村 愛*; 本間 佳哉*; 青木 大*

Journal of the Physical Society of Japan, 88(10), p.103701_1 - 103701_5, 2019/10

The electronic structure of the unconventional superconductor $$mathrm{UTe_2}$$ was studied by resonant photoelectron spectroscopy (RPES) and angle-resolved photoelectron spectroscopy (ARPES) with soft X-ray synchrotron radiation. The partial $$mathrm{U}~5f$$ density of states of $$mathrm{UTe_2}$$ were imaged by the $$mathrm{U}~4d$$ - $$5f$$ RPES and it was found that the $$mathrm{U}~5f$$ state has an itinerant character, but there exists an incoherent peak due to the strong electron correlation effects. Furthermore, an anomalous admixture of the $$mathrm{U}~5f$$ states into the $$mathrm{Te}~5p$$ bands was observed at a higher binding energy, which cannot be explained by band structure calculations. On the other hand, the band structure of $$mathrm{UTe_2}$$ was obtained by ARPES and its overall band structure were mostly explained by band structure calculations. These results suggest that the $$mathrm{U}~5f$$ states of $$mathrm{UTe_2}$$ have itinerant but strongly-correlated nature with enhanced hybridization with the $$mathrm{Te}~5p$$ states.


$$^{125}$$Te-NMR study on a single crystal of heavy fermion superconductor UTe$$_2$$

徳永 陽; 酒井 宏典; 神戸 振作; 服部 泰佑; 比嘉 野乃花; 仲嶺 元輝*; 北川 俊作*; 石田 憲二*; 仲村 愛*; 清水 悠晴*; et al.

Journal of the Physical Society of Japan, 88(7), p.073701_1 - 073701_4, 2019/07

最近新たに発見された重い電子系超伝導体UTe$$_2$$$$^{125}$$Te-NMRによる研究について報告する。単結晶試料を用い$$^{125}$$Te-NMRのKnight shift $$K$$およびスピン-格子緩和率$$1/T_1$$の測定を行なった。その結果、20K以上の常磁性相において静的および動的帯磁率のどちらもが弱いIsing型の異方性を持つことを確認した。一方、20K以下の低温ではa軸方向に磁場をかけた場合にスピン-スピン緩和率$$1/T_2$$の強い発散が見られることがわかった。このことは低温でa軸方向に強い縦型のスピン揺らぎが発達していることを示唆している。


Magnetic and electrical properties of the ternary compound U$$_2$$Ir$$_3$$Si$$_5$$ with one-dimensional uranium zigzag chains

Li, D. X.*; 本多 史憲*; 三宅 厚志*; 本間 佳哉*; 芳賀 芳範; 仲村 愛*; 清水 悠晴*; Maurya, A.*; 佐藤 芳樹*; 徳永 将史*; et al.

Physical Review B, 99(5), p.054408_1 - 054408_9, 2019/02

Physical properties of the single-crystalline U$$_2$$Ir$$_3$$Si$$_5$$, a new ternary uranium compound with U$$_2$$Co$$_3$$Si$$_5$$-type orthorhombic structure, are investigated by means of magnetic susceptibility, specific heat and electrical resistivity. This compound undergoes an antiferromagnetic transition followed by a first-order phase transition at lower temperature. A possible mechanism of the first-order transition is the occurrence of a magnetic magnetic quadrupolar order, resulting from the quasi-one-dimensional uranium zigzag chain.


Effects of magnetic field and pressure on the valence-fluctuating antiferromagnetic compound EuPt$$_2$$Si$$_2$$

竹内 徹也*; 屋良 朝之*; 安次富 洋介*; 伊覇 航*; 垣花 将司*; 中島 美帆*; 天児 寧*; 本多 史憲*; 本間 佳哉*; 青木 大*; et al.

Journal of the Physical Society of Japan, 87(7), p.074709_1 - 074709_14, 2018/07

 被引用回数:2 パーセンタイル:29.91(Physics, Multidisciplinary)

Effects of magnetic field and pressure on the Kondo-like behavior in the valence-fluctuating antiferromagnetic compound EuPt$$_2$$Si$$_2$$ were studied using single-crystalline samples. Anomalous features in EuPt$$_2$$Si$$_2$$ are due to valence fluctuation and/or valence change of the Eu ions at low temperatures.


Easy-plane XY spin fluctuations in the cycloidal magnet UPtGe studied via field orientation-dependent $$^{195}$$Pt NMR

徳永 陽; 仲村 愛*; 青木 大*; 清水 悠晴*; 本間 佳哉*; 本多 史憲*; 酒井 宏典; 服部 泰佑; 神戸 振作

Physical Review B, 98(1), p.014425_1 - 014425_5, 2018/07

 被引用回数:1 パーセンタイル:59.26(Materials Science, Multidisciplinary)



Anisotropic magnetic fluctuations in ferromagnetic superconductor UGe$$_2$$; $$^{73}$$Ge-NQR study at ambient pressure

野間 雄一郎*; 小手川 恒*; 久保 徹郎*; 藤 秀樹*; 播磨 尚朝*; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦*; 伊藤 公平*; Haller, E. E.*; et al.

Journal of the Physical Society of Japan, 87(3), p.033704_1 - 033704_5, 2018/03

 被引用回数:1 パーセンタイル:49.95(Physics, Multidisciplinary)

$$^{73}$$Ge nuclear quadrupole resonance study of ferromagnetic superconductor UGe$$_2$$ is reported. Detailed analyses successfully assigned crystallographic sites of Ge atoms. The measurement of the nuclear spin-lattice relaxation rate revealed highly anisotropic magnetic fluctuations.


Effect of pressure on magnetism of UIrGe

Pospisil, J.; 郷地 順*; 芳賀 芳範; 本多 史憲*; 上床 美也*; 立岩 尚之; 神戸 振作; 長崎 尚子*; 本間 佳哉*; 山本 悦嗣

Journal of the Physical Society of Japan, 86(4), p.044709_1 - 044709_6, 2017/04

 被引用回数:5 パーセンタイル:26.6(Physics, Multidisciplinary)

The effect of hydrostatic pressure on the electronic state of the antiferromagnet UIrGe is reported. A series of resistivity measurements up to 15 GPa demonstrated the Neel temperature decreases with increasing pressure and vanishes around 12 GPa. The transition from antiferromagnetic to paramagnetic phase appears to be of first order. A moderate increase in the effective mass was detected in the vicinity of the critical pressure.


Switching of magnetic ground states across the UIr$$_{1-x}$$Rh$$_x$$Ge alloy system

Pospisil, J.; 芳賀 芳範; 神戸 振作; 徳永 陽; 立岩 尚之; 青木 大*; 本多 史憲*; 仲村 愛*; 本間 佳哉*; 山本 悦嗣; et al.

Physical Review B, 95(15), p.155138_1 - 155138_15, 2017/04

 被引用回数:6 パーセンタイル:30.1(Materials Science, Multidisciplinary)

We investigated the evolution of magnetism in UIr$$_{1-x}$$Rh$$_x$$Ge system by systematic study on high-quality single crystals. We find a field-induced first order transition in the vicinity of the critical magnetic field along the $$b$$ axis in the entire UIr$$_{1-x}$$Rh$$_x$$Ge system, including the ferromagnetic region.


Large reversible magnetocaloric effect in ferromagnetic semiconductor EuS

Li, D. X.*; 山村 朝雄*; 二森 茂樹*; 本間 佳哉*; 本多 史憲*; 芳賀 芳範; 青木 大*

Solid State Communications, 193, p.6 - 10, 2014/09

 被引用回数:10 パーセンタイル:42.74(Physics, Condensed Matter)

We present the large reversible magneto caloric effect of the ferromagnetic semiconductor EuS which shows a maximum magnetic entropy change of 37 J/K kg at 10.4 K, an adiabatic temperature change of 10.4 K and a relative cooling power of 782 J/kg at 18.5 K for a magnetic field change of 5 T. The present results indicate that EuS has excellent refrigeration performance at the temperatures near 20 K, and thus can be considered as the potential magnetic refrigerant material for liquefaction of hydrogen.


Self-radiation effects and glassy nature of magnetic transition in AmO$$_2$$ revealed by $$^{17}$$O-NMR

徳永 陽; 西 剛史; 中田 正美; 伊藤 昭憲*; 酒井 宏典; 神戸 振作; 本間 佳哉*; 本多 史憲*; 青木 大*; Walstedt, R. E.*

Physical Review B, 89(21), p.214416_1 - 214416_8, 2014/06

 被引用回数:6 パーセンタイル:58.6(Materials Science, Multidisciplinary)

AmO$$_2$$の低温の磁気相転移の起源を$$^{17}$$O NMR法により調べた。この相転移については帯磁率では8.5K付近で明確な異常が観測されるが、中性子やメスバウアー分光測定では磁気双極子の秩序は観測されていない。このためNpO$$_2$$と同じ高次多極子の秩序の可能性も指摘されていた。今回我々は新たに$$^{17}$$O核を置換したAmO$$_2$$試料を準備し、それをできる限り短時間でNMR実験サイトへと運び測定を行った。これにより自己照射効果がほぼ存在しない場合の電子状態を確認することができた。さらに同試料を極低温状態に一ヶ月保管することで、自己損傷効果が急激に進み、それによって短時間で試料内の電子状態に変化していく様子を観測することができた。さらにNMRスペクトルの温度依存性と核磁気緩和時間の測定から、AmO$$_2$$の磁気相転移がスピン-グラス的な特徴を持つことも明らかになった。


Competition between magnetic ordering and random spin freezing in Dy$$_2$$PtS$$_3$$

Li, D.*; 山村 朝雄*; 本間 佳哉*; 湯葢 邦夫*; 四竈 樹男*; 青木 大*; 二森 茂樹*; 芳賀 芳範

Journal of the Korean Physical Society, 62(12), p.2233 - 2238, 2013/06

 被引用回数:2 パーセンタイル:73.65(Physics, Multidisciplinary)

We report the results for ac and dc susceptibility, magnetization, magnetic relaxation, specific heat and electrical resistivity measurements on a well annealed ternary intermetallic compound Dy$$_2$$PtSi$$_3$$. An unusual magnetic phase transition with an apparent ferromagnetic nature was observed at $$T_{rm C}$$ = 5.6 K. The classification of Dy$$_2$$PtSi$$_3$$ as a large magnetic cluster (extended short-range ferromagnetic ordered) system with competition between magnetic ordering and random spin freezing seems appropriate.


Anisotropic spin fluctuations in the heavy fermion systems; Case studies of CePd$$_5$$Al$$_2$$ and NpPd$$_5$$Al$$_2$$

酒井 宏典; 中堂 博之; 徳永 陽; 神戸 振作; 芳賀 芳範; Ronning, F.*; Bauer, E. D.*; Thompson, J. D.*; 本間 佳哉*; 青木 大*; et al.

Journal of the Physical Society of Japan, 81(Suppl.B), p.SB003_1 - SB003_6, 2012/12

 被引用回数:3 パーセンタイル:66.83(Physics, Multidisciplinary)

Ce$$T$$In$$_5$$ ($$T$$=Co, Rh, Ir)及び$$An$$$$T$$Ga$$_5$$ ($$An$$=U, Np, Pu)という化学式を持つ一連の化合物(115系と称する)、核磁気共鳴(NMR)測定の結果得られるナイトシフトと緩和率の解析から、反強磁性スピン揺らぎのXY型異方性がd波超伝導発現に有利であるとわかってきた。この仮説を確かめるために、115系化合物と類似の結晶構造を有するCePd$$_5$$Al$$_2$$とNpPd$$_5$$Al$$_2$$においてスピン揺らぎの異方性がどうなっているかを検証した。CePd$$_5$$Al$$_2$$は、イジング異方性を持つ反強磁性体であり、スピン揺らぎも同じくイジング型の異方性を示した。d波超伝導体NpPd$$_5$$Al$$_2$$は、転移温度直上の通常状態においてXY型の反強磁性磁気揺らぎを有していることがわかった。


Single crystal growth and magnetic anisotropy of hexagonal PuGa$$_{3}$$

芳賀 芳範; 本間 佳哉*; 青木 大*; 中島 邦久; 荒井 康夫; 松田 達磨; 池田 修悟*; 酒井 宏典; 山本 悦嗣; 中村 彰夫; et al.

Journal of the Physical Society of Japan, 81(Suppl.B), p.SB007_1 - SB007_4, 2012/12

 パーセンタイル:100(Physics, Multidisciplinary)

We report recent progresses in single crystal preparation as well as physical properties of actinide intermetallic compounds. Flux techniques have successfully been applied for obtain- ing new compounds, including the heavy fermion superconductor NpPd$$_5$$Al$$_2$$ and related compounds. For plutonium compounds, where the radiation damage due to the $$alpha$$-decay of $$^{239}$$Pu is significant, a synthesis technique using the less-radioactive $$^{242}$$Pu isotope has been developed.


Uniaxial-pressure control of magnetic phase transitions in a frustrated magnet CuFe$$_{1-x}$$Ga$$_{x}$$O$$_{2}$$ (x =0, 0.018)

中島 多朗*; 満田 節生*; 高橋 慶一郎*; 吉冨 啓祐*; 増田 一也*; 金子 周史*; 本間 勇紀*; 小林 悟*; 北澤 英明*; 小坂 昌史*; et al.

Journal of the Physical Society of Japan, 81(9), p.094710_1 - 094710_8, 2012/09

We have investigated effects of applied uniaxial pressure ($$p$$) on magnetic phase transitions in a triangular lattice antiferromagnet CuFeO$$_{2}$$ (CFO) and a slightly Ga-substituted compound CuFe$$_{1-x}$$Ga$$_{x}$$O$$_{2}$$ (CFGO) with $$x$$ = 0.018. We have performed neutron diffraction, spherical neutron polarimetry, magnetic susceptibility and pyroelectric measurements under $$p$$ up to 100 MPa applied on the [1$$bar1$$0] surfaces of the single crystal samples.


Uniaxial-pressure control of magnetic phase transitions in a frustrated magnet CuFe$$_{1-x}$$Ga$$_{x}$$O$$_{2}$$ ($$x$$ = 0, 0.018)

中島 多朗*; 満田 節生*; 高橋 慶一郎*; 吉冨 啓祐*; 増田 一也*; 金子 周史*; 本間 勇紀*; 小林 悟*; 北澤 英明*; 小坂 昌史*; et al.

Journal of the Physical Society of Japan, 81(9), p.094710_1 - 094710_8, 2012/09

 被引用回数:9 パーセンタイル:39.11(Physics, Multidisciplinary)

We have investigated effects of applied uniaxial pressure ($$p$$) on magnetic phase transitions in a triangular lattice antiferromagnet CuFeO$$_{2}$$ (CFO) and a slightly Ga-substituted compound CuFe$$_{1-x}$$Ga$$_{x}$$O$$_{2}$$ (CFGO) with $$x$$ = 0.018 by spherical neutron polarimetry. In both of CFO and CFGO ($$x$$ = 0.018), the application of $$p$$ significantly increases the transition temperature from the paramagnetic phase to a collinear incommensurate antiferromagnetic phase. This suggests that the application of $$p$$ breaks equilateral symmetry of the triangular lattice and partially relieves geometrical spin frustration, which generally suppresses long-range magnetic orderings. Thus we demonstrated that uniaxial pressure can be an effective tool to control magnetic phase transitions in frustrated magnets.


Solid-state NMR study of actinide dioxides

徳永 陽; 酒井 宏典; 神戸 振作; 中堂 博之; 逢坂 正彦; 三輪 周平; 西 剛史; 中田 正美; 伊藤 昭憲; 本間 佳哉*

Materials Research Society Symposium Proceedings, Vol.1444, p.149 - 158, 2012/00




Actinide-handling experience for training and education of future expert under J-ACTINET

逢坂 正彦; 小無 健司*; 林 博和; Li, D.*; 本間 佳哉*; 山村 朝雄*; 佐藤 勇; 三輪 周平; 関本 俊*; 窪田 卓見*; et al.

Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 5 Pages, 2011/12



$$^{237}$$Np nuclear relaxation rate in heavy fermion superconductor NpPd$$_5$$ Al$$_2$$

中堂 博之; 徳永 陽; 神戸 振作; 酒井 宏典; 芳賀 芳範; 松田 達磨; 大貫 惇睦; 安岡 弘志; 青木 大*; 本間 佳哉*; et al.

Physical Review B, 84(9), p.094402_1 - 094402_5, 2011/09

 被引用回数:5 パーセンタイル:68.26(Materials Science, Multidisciplinary)

$$^{27}$$Al nuclear spin-lattice relaxation rate 1/$$^{27}$$$$T$$$$_1$$ has been measured in heavy fermion superconductor NpPd$$_5$$Al$$_2$$ for a wide range of external fields between 0.7 and 11 T. We found that 1/$$^{27}$$$$T$$$$_1$$ exhibits a strong, field-dependent behavior at low fields below $$H$$ $$sim$$ 3 T, which is attributed to unlike-spin cross relaxation between $$^{237}$$Np and $$^{27}$$Al. An analysis based on the cross relaxation process allows us to make the first quantitative estimates of the Np nuclear relaxation rate 1/$$^{237}$$$$tau$$ in an itinerant 5$$f$$ electron system. The estimated values of 1/$$^{237}$$$$tau$$ $$sim$$ 6 $$times$$ 10$$^7$$ s$$^{-1}$$, with a weak temperature variation, are below the resolution of NMR relaxation times, indicating that a direct observation of the $$^{237}$$Np NMR signal would be very difficult, at least in the paramagnetic state. It is proposed that a direct observation of $$^{237}$$Np NMR might be possible in the superconducting state at $$T$$ $$sim$$ 1K.


NMR study on AmO$$_{2}$$; Comparison with UO$$_{2}$$ and NpO$$_{2}$$

徳永 陽; 西 剛史; 神戸 振作; 中田 正美; 本間 佳哉*; 酒井 宏典; 中堂 博之

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA110_1 - SA110_3, 2011/07

 被引用回数:2 パーセンタイル:75.59(Physics, Multidisciplinary)



Crystal structure and physical properties of trigonal NpGa$$_3$$ and Np$$_{3}$$Ga$$_{11}$$

芳賀 芳範; 青木 大*; 本間 佳哉*; 松田 達磨; 池田 修悟*; 酒井 宏典; 山本 悦嗣; 中村 彰夫; 塩川 佳伸*; 大貫 惇睦

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA109_1 - SA109_3, 2011/07

 パーセンタイル:100(Physics, Multidisciplinary)

We report reinvestigation the Np-Ga binary system. We successfully obtained NpGa$$_3$$ single crystals. Detailed investigation of the crystal structure using the single-crystal X-ray diffraction has shown that the flux-grown NpGa$$_3$$ crystallizes not in cubic but in the trigonal R$$overline{3}$$m structure. It orders ferromagnetically at 70 K with the saturation moment of 1.5 $$mu_{rm B}$$/Np. It is interesting to note that the cubic NpGa$$_3$$ orders antimagnetically at similar temperature 62 and become ferromagnetic under magnetic field with the similar saturation moment 1.6 $$mu_{rm B}$$/Np. These characteristics are understood from the structural point of view.

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