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論文

Field-induced insulator-metal transition in EuTe$$_2$$

竹内 徹也*; 本多 史憲*; 青木 大*; 芳賀 芳範; 木田 孝則*; 鳴海 康雄*; 萩原 政幸*; 金道 浩一*; 軽部 皓介*; 播磨 尚朝*; et al.

Journal of the Physical Society of Japan, 93(4), p.044708_1 - 044708_10, 2024/04

Electrical and magnetic properties of divalent europium antiferromagnet EuTe$$_2$$ are studied on single crystals grown from Te-flux method. Antiferromagnetism occurs at 11 K with an insulating ground state. Application of magnetic field induces a sudden resistance drop leading to a phase transition to metallic state. Energy band calculations reveal the appearance of a Fermi surface pocket with Te-5p character induced by the polarized Eu moments.

論文

Ferromagnetic crossover within the ferromagnetic order of U$$_{7}$$Te$$_{12}$$

Opletal, P.; 酒井 宏典; 芳賀 芳範; 常盤 欣文; 山本 悦嗣; 神戸 振作; 徳永 陽

Journal of the Physical Society of Japan, 92(3), p.034704_1 - 034704_5, 2023/03

 被引用回数:1 パーセンタイル:0(Physics, Multidisciplinary)

U$$_{7}$$Te$$_{12}$$の単結晶の物理的性質を調べた。U$$_{7}$$Te$$_{12}$$が3つの非等価な結晶ウランサイトを持つ六方晶構造を持つことを確認した。常磁性モーメントは、すべてのサイトで一様なモーメントを仮定すると、ウランサイトあたり約1$$mu_{B}$$と推定される。強磁性相転移は$$T_{rm C}$$=48Kで発生し、面内磁化は急激に増加するが、面外成分はあまり増加しない。磁場冷却条件下で温度がさらに$$T_{rm C}$$以下に低下すると、面外成分はT$$^{star}$$=26K付近で急激に増加する。対照的に、T$$^{star}$$付近で面内成分はほとんど変化しない。比熱測定では、T$$^{star}$$付近に$$lambda$$型の異常がないことが示されているため、これらの振る舞いは、秩序した磁気モーメントの再配向、もしくは複数のウランサイトの連続した逐次磁気転移を示唆している。

論文

Characteristic Fermi surface properties in $$f$$-electron systems

大貫 惇睦*; 摂待 力生*; 芳賀 芳範; 竹内 徹也*; 辺土 正人*; 仲間 隆男*

Quantum Science; The Frontier of Physics and Chemistry, p.21 - 63, 2022/10

Fermi surfaces of $$f$$-electron systems and the novel physical properties related with crystal symmetry, electronic correlations and magnetic interactions are reviewed. The key materials are CeRhIn$$_5$$, CeIr$$_3$$, EuCu$$_2$$Ge$$_2$$ and EuPtSi.

論文

Single crystal growth and magnetic properties of noncentrosymmetric antiferromagnet Mn$$_3$$IrSi

大貫 惇睦*; 金子 良夫*; 青木 大*; 仲村 愛*; 松田 達磨*; 中島 美帆*; 芳賀 芳範; 竹内 徹也*

Journal of the Physical Society of Japan, 91(6), p.065002_1 - 065002_2, 2022/06

 被引用回数:2 パーセンタイル:28(Physics, Multidisciplinary)

Single crystals of Mn$$_3$$IrSi were grown using Bridgman method. Mn$$_3$$IrSi shows a remarkable increase of the electrical resistivity below antiferromagnetic transition temperature accompanied by a large jump of specific heat.

論文

Abrupt change in electronic states under pressure in new compound EuPt$$_3$$Al$$_5$$

小泉 尭嗣*; 本多 史憲*; 佐藤 芳樹*; Li, D.*; 青木 大*; 芳賀 芳範; 郷地 順*; 長崎 尚子*; 上床 美也*; 金子 良夫*; et al.

Journal of the Physical Society of Japan, 91(4), p.043704_1 - 043704_5, 2022/04

 被引用回数:2 パーセンタイル:46.35(Physics, Multidisciplinary)

A new ternary europium compound EuPt$$_3$$Al$$_5$$ is reported. It orders antiferromagnetically at 12.4 K. Application of hydrostatic pressure varies the transition temperature and the compound becomes non-magnetic above the critical pressure 9 GPa. The pressure-temperature phase diagram is indicative of a possible valence crossover at the critical pressure.

論文

Half-integer Shapiro steps in strong ferromagnetic Josephson junctions

Yao, Y.*; Cai, R.*; Yang, S.-H.*; Xing, W.*; Ma, Y.*; 森 道康; Ji, Y.*; 前川 禎通; Xie, X.-C.*; Han, W.*

Physical Review B, 104(10), p.104414_1 - 104414_6, 2021/09

 被引用回数:2 パーセンタイル:7.92(Materials Science, Multidisciplinary)

We report the experimental observation of half-integer Shapiro steps in the strong ferromagnetic Josephson junction (Nb-NiFe-Nb) by investigating the current-phase relation under radio-frequency microwave excitation. The half-integer Shapiro steps are robust in a wide temperature range from T = 4 to 7 K. The half-integer Shapiro steps could be attributed to co-existence of 0- and $$pi$$-states in the strong ferromagnetic NiFe Josephson junctions with the spatial variation of the NiFe thickness. This scenario is also supported by the high-resolution transmission electron microscopy characterization of the Nb/NiFe/Nb junction.

論文

Anisotropic physical properties of layered antiferromagnet U$$_2$$Pt$$_6$$Ga$$_{15}$$

松本 裕司*; 芳賀 芳範; 山本 悦嗣; 竹内 徹也*; 三宅 厚志*; 徳永 将史*

Journal of the Physical Society of Japan, 90(7), p.074707_1 - 074707_6, 2021/07

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

A uranium intermetallic compound U$$_2$$Pt$$_6$$Ga$$_{15}$$ was successfully synthesized. This compound crystallizes in the hexagonal Sc$$_{0.6}$$Fe$$_2$$Si$$_{4.9}$$-type structure. Antiferromagnetic transition with highly magnetic anisotropy was established by the physical property measurements.

論文

Observation of longitudinal magnetic fluctuations at a first-order ferromagnetic quantum phase transition in UGe$$_2$$

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*; 仲村 愛*; et al.

Journal of the Physical Society of Japan, 90(7), p.073707_1 - 073707_5, 2021/07

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

Ferromagnetic fluctuation relevant to the pressure-induced superconductivity in UGe$$_2$$ is investigated by means of NMR spectroscopy. Longitudinal magnetic fluctuations were observed in the spin-echo decay rate near the ferromagnetic critical point where superconductivity takes place. This result strongly suggests that superconductivity in ferromagnets is universally mediated by anisotropic magnetic fluctuations.

論文

Nonmagnetic-magnetic transition and magnetically ordered structure in SmS

吉田 章吾*; 小山 岳秀*; 山田 陽彦*; 中井 祐介*; 上田 光一*; 水戸 毅*; 北川 健太郎*; 芳賀 芳範

Physical Review B, 103(15), p.155153_1 - 155153_5, 2021/04

 被引用回数:1 パーセンタイル:0(Materials Science, Multidisciplinary)

SmS, a protopypical intermediate valence compound, has been studied by performing high-pressure nuclear magnetic resonance measurements. The observation of an additional signal at high pressure gives evidence of a magnetic phase transition. The cancellation of the hyperfined fields at the S site suggests a type-II antiferromagnetic structure.

論文

Intriguing behavior of UCo$$_{1-x}$$Rh$$_x$$Ge ferromagnets in magnetic field along the $$b$$ axis

Posp$'i$$v{s}$il, J.*; 芳賀 芳範; 三宅 厚志*; 神戸 振作; 徳永 陽; 徳永 将史*; 山本 悦嗣; Proschek, P.*; Voln$'y$, J.*; Sechovsk$'y$, V.*

Physical Review B, 102(2), p.024442_1 - 024442_13, 2020/07

 被引用回数:6 パーセンタイル:38.95(Materials Science, Multidisciplinary)

Alloying study of ferromagnetic superconductors URhGe and UCoGe is reported. The Curie temperature shows a maximum at Rh concentration $$x$$ = 0.4 in UCo$$_{1-x}$$Rh$$_x$$Ge. Magnetic characteristices in low- and high-$$x$$ regions are significantly different each other. The relationship between magnetism and superconductivity are discussed.

論文

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.

論文

Heavy fermion state of YbNi$$_2$$Si$$_3$$ without local inversion symmetry

中村 翔太*; 兵頭 一志*; 松本 裕司*; 芳賀 芳範; 佐藤 仁*; 上田 茂典*; 三村 功次郎*; 斉木 克祥*; 磯 孝斉*; 山下 穣*; et al.

Journal of the Physical Society of Japan, 89(2), p.024705_1 - 024705_5, 2020/02

 被引用回数:2 パーセンタイル:22.16(Physics, Multidisciplinary)

We have succeeded in growing a new heavy fermion compound YbNi$$_2$$Si$$_3$$ by the flux method. From electrical resistivity, magnetization, specific heat, magnetic torque and X-ray photoemission measurements concluded that this compound is a heavy fermion compound exhibiting an antiferromagnetic order at 0.35 K.

論文

Anomalous ferromagnetic ordering in EuCuP

伊覇 航*; 垣花 将司*; 松田 進弥*; 本多 史憲*; 芳賀 芳範; 竹内 徹也*; 中島 美帆*; 天児 寧*; 郷地 順*; 上床 美也*; et al.

Journal of Alloys and Compounds, 788, p.361 - 366, 2019/06

 被引用回数:6 パーセンタイル:33.98(Chemistry, Physical)

Ferromagnetic ordering of EuCuP is investigated on a single crystal sample grown from tin flux. Application of hydrostatic pressure up to 8 GPa stabilizes ferromagnetic ordering, suggesting divalent Eu is stable. The Hall effect and resistivity measurements show that EuCuP is a low-carrier ferromagnetic metal with a characteristic resistivity cusp appearing at the ferromagnetic transition temperature.

論文

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

 被引用回数:5 パーセンタイル:27.67(Materials Science, Multidisciplinary)

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.

論文

Magnetization study on the Ising ferromagnet URhGe with high-precision angle-resolved magnetic field near the hard axis

中村 翔太*; 榊原 俊郎*; 清水 悠晴*; 橘高 俊一郎*; 河野 洋平*; 芳賀 芳範; Pospisil, J.; 山本 悦嗣

Progress in Nuclear Science and Technology (Internet), 5, p.123 - 127, 2018/11

Dc magnetization measurements have been performed on the orthorhombic Ising ferromagnet Urge. We observed a clear first-order reorientation transition with a small hysteresis and estimated the tricritical point to be around 4 K. The magnetization and the thermal expansion data indicate the presence of a characteristic temperature of about 1 K.

論文

Anomalous Hall effect in a triangular-lattice antiferromagnet UNi$$_4$$B

小山田 明*; 猪原 崇生*; 山本 悦嗣; 芳賀 芳範

Progress in Nuclear Science and Technology (Internet), 5, p.128 - 131, 2018/11

We report the Hall effect measurements on a triangular-lattice antiferromagnet UNi$$_4$$B in the context of the proposed relevance of the ferroic order. Our measurements show that the Hall voltage is proportional to the square of the electric current and its coefficient increases significantly below the transition temperature, which supports the theoretical prediction.

論文

Crystal structure and magnetic properties of new ternary uranium compound U$$_3$$TiBi$$_9$$

本山 岳*; 芳賀 芳範; 山口 明*; 川崎 郁斗*; 住山 昭彦*; 山村 朝雄*

Progress in Nuclear Science and Technology (Internet), 5, p.157 - 160, 2018/11

The crystal structure of the newly discovered compound U$$_3$$TiBi$$_9$$ was determined from single-crystal X-ray diffraction data. This compound shows an antiferromagnetic ordering at 31.5 K. A clear anomaly was observed at the transition temperature on the temperature dependence of magnetic susceptibility and electrical resistivity.

論文

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:12 パーセンタイル:64.96(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.

論文

Magnetic field induced phenomena in UIrGe in fields applied along the $$b$$ axis

Posp$'i$$v{s}$il, J.*; 芳賀 芳範; 小濱 芳允*; 三宅 厚志*; 神戸 振作; 立岩 尚之; Vali$v{s}$ka, M.*; Proschek, P.*; Prokle$v{s}$ka, J.*; Sechovsk$'y$, V.*; et al.

Physical Review B, 98(1), p.014430_1 - 014430_7, 2018/07

 被引用回数:16 パーセンタイル:61.77(Materials Science, Multidisciplinary)

The metamagnetic transition between the antiferromagnetic and paramagnetic state in UIrGe has been studied at various temperatures by magnetization, heat capacity, and magnetocaloric effect measurements on a single crystal in static and pulsed magnetic fields applied along the orthorhombic $$b$$ axis. The first-order transition is accompanied by a dramatic increase of the Sommerfeld coefficient. A tentative scenario explaining these anomalies by antiferromagnetic correlations or short-range order in the paramagnetic state is discussed.

論文

Electronic states in EuCu$$_2$$(Ge$$_{1-x}$$Si$$_x$$)$$_2$$ based on the doniach phase diagram

伊覇 航*; 屋良 朝之*; 安次富 洋介*; 垣花 将司*; 竹内 徹也*; 本多 史憲*; 仲村 愛*; 青木 大*; 郷地 順*; 上床 美也*; et al.

Journal of the Physical Society of Japan, 87(6), p.064706_1 - 064706_14, 2018/06

 被引用回数:19 パーセンタイル:75.67(Physics, Multidisciplinary)

We succeeded in growing single crystals of the series of EuCu$$_2$$(Ge$$_{1-x}$$Si$$_x$$)$$_2$$ compounds.Physical property measurements demonstrate a maximum of the antiferromagnetic transition temperature appears at $$x = 0.5$$. Antiferromagnetism then disappears around $$x = 0.7$$ followed by a heavy-fermion formation at higher concentrations. These observations follow the Doniach phase diagram as a function of $$x$$.

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