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論文

Single crystal growth and physical properties of ternary uranium compounds U$${M_2}$$Al$$_{10}$$ ($$M$$=Fe, Ru and Os)

菅井 孝志; 芳賀 芳範; 松田 達磨; 山本 悦嗣; 立岩 尚之; 本多 史憲*; 摂待 力生*; 大貫 惇睦

Journal of Physics; Conference Series, 273, p.012122_1 - 012122_4, 2011/02

 被引用回数:0 パーセンタイル:0.03

We investigated the ternary uranium compounds U$${M_2}$$Al$$_{10}$$ ($$M$$ = Fe, Ru and Os) with the orthorhombic YbFe$$_2$$Al$$_{10}$$-type crystal structure. URu$$_2$$Al$$_{10}$$ and UOs$$_2$$Al$$_{10}$$ are new compounds grown for the first time. These compounds show no ordering despite the Curie-Weiss behavior at high temperatures. The temperature dependence of the electrical resistivity, the specific heat and the magnetic susceptibility indicate that U$${M_2}$$Al$$_{10}$$ ($$M$$ = Fe, Ru and Os) has non-magnetic ground states.

論文

Relation between metamagnetic transition and quantum critical point in heavy fermion compound YbIr$$_2$$Zn$$_{20}$$

大貫 惇睦; 安井 慎一*; 吉内 伸吾*; 大家 政洋*; 松下 昌輝*; 広瀬 雄介*; 竹内 徹也*; 本多 史憲*; 摂待 力生*; 杉山 清寛*; et al.

Journal of Physics; Conference Series, 273, p.012013_1 - 012013_4, 2011/02

 被引用回数:0 パーセンタイル:0.03

Metamagnetic behavior of the heavy fermion compound YbIr$$_2$$Zn$$_{20}$$ has been studied experimentally. The metamagnetic transition was clearly seen in the bulk magnetization curve. Near the metamagnetic critical field H$$_m$$ $$sim$$ 100 kOe, the effective mass of conduction electrons exhibits a significant enhancements. It is suggested that the present metamagnetism is related to the magnetic instability around the quantum critical point.

論文

Magnetization in the superconducting mixed state of the heavy-fermion compound UBe$$_{13}$$

清水 悠晴*; 池田 陽一*; 若林 琢巳*; 天谷 健一*; 芳賀 芳範; 日高 宏之*; 柳澤 達也*; 網塚 浩*

Journal of Physics; Conference Series, 273, p.012084_1 - 012084_4, 2011/02

 被引用回数:3 パーセンタイル:66.37

Static dc magnetization measurements in the superconducting mixed state of a single crystal UBe$$_{13}$$ were performed by means of a capacitance Faraday-force method down to 0.24 K. Below the upper critical field $$B_{c2}$$, not only a peak effect but also an additional broad anomaly have been observed in magnetization curves. We report superconducting phase diagram of UBe$$_{13}$$ obtained by our magnetization measurements, including these anomalies.

論文

Electronic structure of U(Ru$$_{1-x}$$Rh$$_{x}$$)$$_2$$Si$$_2$$ studied by laser angle-resolved photoemission spectroscopy

吉田 力矢*; 中村 祥明*; 福井 仁紀*; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦; 大川 万里生*; Shin, S.*; 平井 正明*; 村岡 祐治*; et al.

Journal of Physics; Conference Series, 273, p.012021_1 - 012021_4, 2011/02

 被引用回数:0 パーセンタイル:0.03

Electronic structures of U(Ru$$_{1-x}$$Rh$$_x$$)$$_2$$Si$$_2$$ is studied employing ultrahigh-resolution laser angle-resolved photoemission spectroscopy. A hole-like dispersive feature, which presumably has Rh $$d$$-band character, was observed.However, although a heavy quasiparticle band appears in the hidden-order state of URu$$_2$$Si$$_2$$ ($$x$$ = 0), it was not observed for $$x$$ = 0.03 over the temperature range studied.

論文

Soft X-ray angle-resolved photoemission study of YbCu$$_2$$Ge$$_2$$

保井 晃; 藤森 伸一; 川崎 郁斗; 岡根 哲夫; 竹田 幸治; 斎藤 祐児; 山上 浩志; 関山 明*; 摂待 力生*; 松田 達磨; et al.

Journal of Physics; Conference Series, 273, p.012067_1 - 012067_4, 2011/02

 被引用回数:3 パーセンタイル:66.37

これまでYb2価物質であると考えられてきたYbCu$$_2$$Ge$$_2$$について、Yb4$$f$$電子を含む固体内部の電子構造を調べるために軟X線光電子分光実験を行った。その結果、角度積分スペクトルの結合エネルギーの6$$sim$$12eVにわずかにYb$$^{3+}$$多重項ピークが観測された。これはYbCu$$_2$$Ge$$_2$$は価数揺動物質であることを示している。また、角度分解スペクトルにおいてYb4$$f$$バンドと伝導バンドが"anti-crossing"している様子が確認できた。これは、Ge4$$p$$とCu3$$d$$でできた伝導バンドとYb4$$f$$バンドが混成していることを示す。

論文

Anomalous low-field diamagnetic response in ultraclean URu$$_2$$Si$$_2$$ superconductor

岡崎 竜二*; 下澤 雅明*; 宍戸 寛明*; Konczykowski, M.*; 芳賀 芳範; 松田 達磨; 山本 悦嗣; 大貫 惇睦; 柳瀬 陽一*; 芝内 孝禎*; et al.

Journal of Physics; Conference Series, 273, p.012081_1 - 012081_4, 2011/02

 被引用回数:3 パーセンタイル:66.37

The low critical field $$H_{rm c1}$$ in ultraclean URu$$_2$$Si$$_2$$ single crystals with residual resistivity ration exceeding 700 is precisely determined. The whole $$H_{rm c1}$$ for $$H parallel a$$ can be explained by the two-gap with line and point nodes. In contrast, for $$H parallel c$$ a distinct kink in the slope of $$H_{rm c1}$$ was found at 1.2 K, which cannot be accounted for by the two-gap. This outstanding anomaly demonstrates a highly unusual superconducting state embedded in the hidden order state possibly related to the time reversal symmetry breaking.

論文

High-pressure electrical resistivity measurement on heavy fermion superconductor URu$$_2$$Si$$_2$$ using super clean crystal

立岩 尚之; 松田 達磨; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦

Journal of Physics; Conference Series, 273, p.012087_1 - 012087_5, 2011/02

 被引用回数:4 パーセンタイル:73.87

URu$$_2$$Si$$_2$$の高圧下電気抵抗測定を高純度単結晶試料を用いて行った。圧力相図を再検討した。圧力を加えると、隠れた秩序相への相転移温度は増大し、超伝導転移温度は単調に減少してゆく。基底状態が隠れた秩序相である臨界圧力$$P_x$$未満では、電気抵抗の温度のべきは2より小さくなることが明らかにされた。これは通常のフェルミ流体理論と異なる結果であり、隠れた秩序相の特性であることが明らかにされた。

口頭

Unconventional magnetism and superconductivity in the ternary actinide compounds AnPd$$_5$$Al$$_2$$

芳賀 芳範

no journal, , 

AnPd$$_5$$Al$$_2$$ compounds (An = rare earths and actinides) crystallize in the tetragonal ZrNi$$_2$$Al$$_5$$-type structure. Among them, NpPd$$_5$$Al$$_2$$ is the first Np compound that shows heavy fermion superconductivity. The strongly Pauli-limited upper critical fields (Hc$$_2$$) reflecting the magnetic anisotropy and the first-order phase transition at Hc$$_2$$ are very similar characteristics as observed in other heavy fermions. Detailed magnetic and superconducting study for these compounds including new experimental developments particularly for the transuranium compounds will be discussed.

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