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論文

Crossover phase diagram and electronic state in the heavy-fermion metamagnets UIr$$_2$$Zn$$_{20}$$ and UCo$$_2$$Zn$$_{20}$$

広瀬 雄介*; 竹内 徹也*; 本多 史憲*; 吉内 伸吾*; 萩原 政幸*; 山本 悦嗣; 芳賀 芳範; 摂待 力生*; 大貫 惇睦

Journal of the Physical Society of Japan, 84(7), p.074704_1 - 074704_10, 2015/07

 被引用回数:5 パーセンタイル:43.76(Physics, Multidisciplinary)

Magnetic phase diagram of two heavy fermion metamagnets UIr$$_2$$Zn$$_{20}$$ and UCo$$_2$$Zn$$_{20}$$ is investigated. UIr$$_2$$Zn$$_{20}$$ shows a reconstruction of the electronic states across the metamagnetic crossover. However, UCo$$_2$$Zn$$_{20}$$ shows a rather continuous evolution. The remarkable difference in both compounds can be accounted for by different degree of hybridization between 5$$f$$ and ligand electrons.

論文

Transport properties of UT$$_2$$Zn$$_{20}$$ (T: Co, Ir)

広瀬 雄介*; 竹内 徹也*; 吉内 伸吾*; 山本 悦嗣; 芳賀 芳範; 摂待 力生*; 大貫 惇睦

JPS Conference Proceedings (Internet), 3, p.011056_1 - 011056_6, 2014/06

Transport properties of UT$$_2$$Zn$$_{20}$$ (T: Co, Ir) have been investigated by measuring Hall effect. Overall behavior is explained by the skew scattering on the impurity model at high temperatures and the periodic Anderson model at low temperatures. Rather complicated behavior was observed in UIr$$_2$$Zn$$_{20}$$ with ferromagnetic instability, implying the electronic modification under magnetic field.

論文

Single crystal growth and various electronic states in Yb-based compounds

広瀬 雄介*; 吉内 伸吾*; 西村 尚人*; 阪口 準也*; 榎 健太郎*; 岩川 健*; 三浦 泰直*; 杉山 清寛*; 大貫 惇睦; 摂待 力生*; et al.

Journal of the Korean Physical Society, 62(12), p.1858 - 1861, 2013/06

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

We succeeded in growing single crystals of YbTIn$$_5$$ (T: Co, Rh, Ir), YbGa$$_4$$, YbT$$_2$$Zn$$_{20}$$ (T: Co, Rh, Ir), etc. The electronic and magnetic properties are clarified by measuring the electrical resistivity, magnetic susceptibility, magnetization, specific heat and de Haas-van Alphen effect.

論文

Electronic states in antiferromagnet UCd$$_{11}$$ and reference compound ThCd$$_{11}$$; Studied by the de Haas-van Alphen effect

広瀬 雄介*; 三浦 泰直*; 堤 泰樹*; 吉内 伸吾*; 大家 政洋*; 杉山 清寛*; 竹内 徹也*; 山上 浩志*; 山本 悦嗣; 芳賀 芳範; et al.

Physica Status Solidi (B), 250(3), p.642 - 645, 2013/03

 被引用回数:3 パーセンタイル:77.51(Physics, Condensed Matter)

Electronic states of an antiferromagnet UCd$$_{11}$$ and its reference compound ThCd$$_{11}$$ were investigated by means of de Haas-van Alphen (dHvA) effect. From the cyclotron effective mass determined from the dHvA oscillation, the electronic specific heat of UCd$$_{11}$$ was estimated as 100 mJ/K$$^2$$mol, much smaller than 840 in the previous report. The result suggests that magnetic excitation contributes significantly to the specific heat.

論文

Electrical and magnetic properties of quasicrystal approximants RCd$$_6$$ (R: rare earth)

森 晶宣*; 太田 尚志*; 吉内 伸吾*; 岩川 健*; 田賀 悠記*; 広瀬 雄介*; 竹内 徹也*; 山本 悦嗣; 芳賀 芳範; 本多 史憲*; et al.

Journal of the Physical Society of Japan, 81(2), p.024720_1 - 024720_10, 2012/02

 被引用回数:15 パーセンタイル:27.79(Physics, Multidisciplinary)

Single crystals of quasicrystal approximants RCd$$_6$$ (R: rare earths) were prepared using the self-flux method and subsequent annealing. A structural transition was confirmed in some of these crystals. Antiferromagnetic ordering was observed for R = Nd, Sm, Tb and Dy. It was found that the structural order-disorder transition has a great influence on the magnetic ordering and transport properties.

論文

Characteristic heavy fermion properties in YbCu$$_2$$Si$$_2$$ and YbT$$_2$$Zn$$_{20}$$ (T: Co, Rh, Ir)

大貫 惇睦; 安井 慎一*; 松下 昌輝*; 吉内 伸吾*; 大家 政洋*; 広瀬 雄介*; Dung, N. D.*; 本多 史憲*; 竹内 徹也*; 摂待 力生*; et al.

Journal of the Physical Society of Japan, 80(Suppl.A), p.SA003_1 - SA003_6, 2011/12

We studied the Fermi surface properties of YbCu$$_2$$Si$$_2$$ and YbCu$$_2$$Ge$$_2$$ with the tetragonal structure by measuring the de Haas-van Alphen (dHvA) oscillations, together with the energy band calculations. It was clarified that 4f electrons contribute to the Fermi surface of a valence fluctuating compound YbCu$$_2$$Si$$_2$$, but not to that of a divalent compound YbCu$$_2$$Ge$$_2$$. We also studied the heavy fermion properties of YbT$$_2$$Zn$$_{20}$$ (T: Co, Rh, Ir) with the cubic caged structure. The metamagnetic behavior or an abrupt nonlinear increase of magnetization was observed. By measuring the electrical resistivity under pressure and magnetic field, we clarified that the electronic state close to the quantum critical point is realized in YbIr$$_2$$Zn$$_{20}$$ at 5.2 GPa and also YbCo$$_2$$Zn$$_{20}$$ at ambient pressure.

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

 パーセンタイル:100

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

Metamagnetic behavior in heavy-fermion compound YbIr$$_2$$Zn$$_{20}$$

竹内 徹也*; 安井 慎一*; 戸田 雅敏*; 松下 昌輝*; 吉内 伸吾*; 大家 政洋*; 片山 敬亮*; 広瀬 雄介*; 吉谷 尚久*; 本多 史憲*; et al.

Journal of the Physical Society of Japan, 79(6), p.064609_1 - 064609_15, 2010/06

 被引用回数:37 パーセンタイル:13.7(Physics, Multidisciplinary)

Metamagnetic behavior of the heavy-fermion compound YbIr$$_2$$Zn$$_{20}$$ was studied by magnetization, de Haas-van Alphen effect, magnetoresistance, specific heat, thermal expansion and magnetostriction. Metamagnetic behavior was observed for all the physical properties at low temperatures. It is remarkable that the Fermi surfaces observed in the dHvA effect unchanges across the metamagnetic transition.

論文

Low-temperature magnetic orderings and Fermi surface properties of LaCd$$_{11}$$, CeCd$$_{11}$$, and PrCd$$_{11}$$ with a caged crystal structure

吉内 伸吾*; 竹内 徹也*; 大家 政洋*; 片山 敬亮*; 松下 昌輝*; 吉谷 尚久*; 西村 尚人*; 太田 尚志*; 立岩 尚之; 山本 悦嗣; et al.

Journal of the Physical Society of Japan, 79(4), p.044601_1 - 044601_11, 2010/04

 被引用回数:11 パーセンタイル:36(Physics, Multidisciplinary)

We succeeded in growing single crystals of cage-structure compounds RCd$$_{11}$$ (R: La, Ce, and Pr) and precisely studied their low-temperature magnetic and electronic properties. We found antiferromagnetic ordering at 0.44 and 0.39 K in CeCd$$_{11}$$ and PrCd$$_{11}$$, respectively, and clarified the magnetic phase diagrams of the compounds. From the dHvA experiment, we detected small dHvA branches ranging from 7$$times$$10$$^5$$ to 2$$times$$10$$^7$$ Oe, which correspond to small Fermi surfaces. This is mainly due to a small Brillouin zone based on a large unit cell. Moreover, the dHvA frequencies and cyclotron masses are approximately the same among RCd$$_{11}$$, revealing a localized character of 4f electrons in CeCd$$_{11}$$ and PrCd$$_{11}$$.

論文

Heavy fermion state in YbIr$$_2$$Zn$$_{20}$$

吉内 伸吾*; 戸田 雅敏*; 松下 昌輝*; 安井 慎一*; 広瀬 雄介*; 大家 政洋*; 片山 敬亮*; 本多 史憲*; 杉山 清寛*; 萩原 政幸*; et al.

Journal of the Physical Society of Japan, 78(12), p.123711_1 - 123711_4, 2009/12

 被引用回数:37 パーセンタイル:13.97(Physics, Multidisciplinary)

High-field magnetization and de Haas-van Alphen effect were measured on a heavy fermion compound YbIr$$_2$$Zn$$_{20}$$. Large cyclotron masses ranging from 4 to 27 $$m_0$$ were detected in the dHvA experiment, and are found to be reduced at magnetic fields higher than 120 kOe. From the present experimental results together with the 4f-itinerant band calculations, the 4f electrons are considered to form heavy fermion state.

口頭

重い電子系化合物YbCo$$_2$$Zn$$_{20}$$の中性子非弾性散乱実験及び磁場効果

金子 耕士; 吉内 伸吾*; 竹内 徹也*; 本多 史憲*; 摂待 力生*; 大貫 惇睦

no journal, , 

Yb$$T_2$$Zn$$_{20}$$の中でも$$T$$=Coでは、電子比熱係数$${gamma}$$が8J/mol K$$^2$$近い極めて重い電子状態が実現し、かつ強い磁場依存性を示すことが報告されている。中性子非弾性散乱により、f電子状態を微視的視点から調べた。その結果、低温では重い電子状態に起因する強い準弾性散乱を観測するとともに、結晶場励起に対応する鋭いピークを0.6meVに観測した。このうち、準弾性散乱については、磁場とともに強くdumpすることを見いだした。これらの観測結果から、結晶場モデルや磁場応答について議論する。

口頭

Spin dynamics of heavy-fermion compound YbCo$$_2$$Zn$$_{20}$$

金子 耕士; 吉内 伸吾*; 竹内 徹也*; 本多 史憲*; 摂待 力生*; 大貫 惇睦

no journal, , 

YbT$$_2$$Zn$$_{20}$$ is known to exhibit heavy-fermion behavior. In particular, YbCo$$_2$$Zn$$_{20}$$ shows extremely large electronic specific coefficient at ambient pressure. In order to get detailed insights into f-electron state in YbCo$$_2$$Zn$$_{20}$$, neutron scattering experiments were carried out. In neutron inelastic spectra at 300 mK, strong quasielastic scattering together with an apparent peak at 0.6 meV was observed. With increasing temperature to 10 K, a broad peak comes up around 2.1 meV, whereas quasielastic response gets broader and the peak at 0.6 meV is buried in the quasielastic one. The observed quasielastic scattering can be ascribed as Kondo-type spin fluctuation with a characteristic energy scale $${Gamma}$$ of 0.3 meV. The observed peaks at 0.6 and 2.1 meV can be assigned as crystal-field excitations. Coexistence of both the quasielastic scattering and the sharp crystal-field excitations characterizes the f-electron state in YbCo$$_2$$Zn$$_{20}$$.

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