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論文

Robustness of ferromagnetism in van der Waals magnet FeGeTe to hydrostatic pressure

Wang, Y.*; Zeng, X.-T.*; Li, B.*; Su, C.*; 服部高典; Sheng, X.-L.*; Jin, W.*

Chinese Physics B, 34(4), p.046203_1 - 046203_6, 2025/03

https://doi.org/10.1088/1674-1056/adb26f

被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

二次元ファンデルワールス強磁性体FeGeTe(FGT)は、その高いキュリー温度、容易な調整性、空気中での優れた構造安定性から、スピントロニクスデバイスへの応用に大きな可能性を秘めている。理論的研究により、外部パラメータとしての圧力が強磁性特性に大きく影響することが示されている。本研究では、5GPaまでの高圧中性子粉末回折(NPD)実験を行い、FGTの静水圧による構造及び磁気特性の変化を調べた。NPDデータは、静水圧による見かけ上の抑制にもかかわらず、FGTにおける強磁性の頑健性を明らかにした。圧力が0から5GPaまで増加すると、キュリー温度は225(5)Kから175(5)Kまで単調減少し、Feの秩序モーメントが劇的に抑制されることがわかった。圧力による構造相転移は5GPaまで観測されなかったが、結合長と結合角の変化を定量的に解析した結果、交換相互作用が大きく変化していることがわかった。

論文

Electronic phase diagram of itinerant electron metamagnet UCoAl

前田瑞穂*; 松田達磨*; 芳賀芳範; 白崎謙次*; 木村憲彰*

Journal of the Physical Society of Japan, 94(2), p.024707_1 - 024707_6, 2025/01

https://doi.org/10.7566/JPSJ.94.024707

被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

We investigate the pressure dependence of the magnetoresistivity and Hall resistivity for an itinerant-electron metamagnet UCoAl. The first-order metamagnetic transition point varies as a function of hydrostatic pressure and terminates at the critical pressure 2.0 GPa. The electronic system, however, does not show criticality at this pressure but extends to higher pressures, unlike the usual quantum critical behavior.

論文

Antiferromagnetism and phase stability of CrMnFeCoNi high-entropy alloy

Zhu, L.*; He, H.*; Naeem, M.*; Sun, X.*; Qi, J.*; Liu, P.*; Harjo, S.; 中島健次; Li, B.*; Wang, X.-L.*

Physical Review Letters, 133(12), p.126701_1 - 126701_6, 2024/09

https://doi.org/10.1103/PhysRevLett.133.126701

被引用回数：4 パーセンタイル：70.50(Physics, Multidisciplinary)

It has long been suspected that magnetism could play a vital role in the phase stability of multi- component high-entropy alloys. However, the nature of the magnetic order, if any, has remained elusive. Here, by using elastic and inelastic neutron scattering, we demonstrate evidence of antiferromagnetic order below 80 K and strong spin fluctuations persisting to room temperature in a single-phase face-centered cubic (fcc) CrMnFeCoNi high-entropy alloy. Despite the chemical complexity, the magnetic structure in CrMnFeCoNi can be described as -Mn-like, with the magnetic moments confined in alternating (001) planes and pointing toward the 111 direction. Combined with first-principles calculation results, it is shown that the antiferromagnetic order and spin fluctuations help stabilized the fcc phase in CrMnFeCoNi high-entropy alloy.

論文

Dramatic elastic response at the critical end point in UTe

Valika, M.*; Haidamak, T.*; Cabala, A.*; Pospil, J.*; Bastien, G.*; Sechovsk, V.*; Prokleka, J.*; 柳澤達也*; Opletal, P.; 酒井宏典; et al.

Physical Review Materials (Internet), 8(9), p.094415_1 - 094415_9, 2024/09

https://doi.org/10.1103/PhysRevMaterials.8.094415

被引用回数：2 パーセンタイル：30.91(Materials Science, Multidisciplinary)

Elastic responses at the metamagnetic transition in UTe are studied at high field. The elastic anomaly becomes the strongest at the critical-end-point. Similar behavior was also observed in another metamagnet UCoAl, suggesting a universal elastic response triggered by critical magnetic fluctuations.

論文

Field-induced insulator-metal transition in EuTe

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

https://doi.org/10.7566/JPSJ.93.044708

被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

Electrical and magnetic properties of divalent europium antiferromagnet EuTe 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

Quantum critical behavior of the hyperkagome magnet MnCoSi

山内宏樹; Sari, D. P.*; 安井幸夫*; 坂倉輝俊*; 木村宏之*; 中尾朗子*; 大原高志; 本田孝志*; 樹神克明; 井川直樹; et al.

Physical Review Research (Internet), 6(1), p.013144_1 - 013144_9, 2024/02

https://doi.org/10.1103/PhysRevResearch.6.013144

-Mn-type family alloys Mn have three-dimensional antiferromagnetic (AFM) corner-shared triangular network. The antiferromagnet MnRhSi shows magnetic short-range order (SRO) over a wide temperature range of approximately 500 K above the Nel temperature $T_{rm N}$ = 190 K. MnCoSi has the smallest lattice parameter and the lowest $T_{rm N}$ in the family compounds. The quantum critical point (QCP) from AFM to the quantum paramagnetic state is expected near a cubic lattice parameter of 6.15 of MnCoSi is only 140 K, quantum critical behavior is observed in MnCoSi as the enhancement of the electronic specific heat coefficient . We study how the magnetic SRO appears in MnCoSi by using neutron scattering, SR, and physical property measurements. The experimental results show that the neutron scattering intensity of the magnetic SRO does not change much regardless of the suppressed magnetic moment in the long-range magnetic ordered state compared to those of MnRhSi. The initial asymmetry drop ratio of SR above $T_{rm N}$ becomes small, and the magnetic SRO temperature $T_{SRO}$ is suppressed to 240 K. The results suggest that the MnCoSi is close to the QCP in the Mn system.

論文

Fully gapped pairing state in spin-triplet superconductor UTe

末次祥大*; 酒井宏典; Opletal, P.; 常盤欣文; 芳賀芳範; 他12名*

Science Advances (Internet), 10(6), p.eadk3772_1 - eadk3772_6, 2024/02

https://doi.org/10.1126/sciadv.adk3772

被引用回数：22 パーセンタイル：97.38(Multidisciplinary Sciences)

The superconducting gap structure of UTe was determined by the thermal conductivity measurement on ultra-clean UTe single crystals. The result demonstrates the absence of nodes around the -axis, contrary to the previous study. The finding reveals that UTe is likely to be a long-sought three-dimensional strong topological superconductor.

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

https://doi.org/10.7566/JPSJ.92.034704

被引用回数：3 パーセンタイル：44.05(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 -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

https://doi.org/10.1007/978-981-19-4421-5_2

Fermi surfaces of -electron systems and the novel physical properties related with crystal symmetry, electronic correlations and magnetic interactions are reviewed. The key materials are CeRhIn, CeIr, EuCuGe and EuPtSi.

論文

Magnetic Bragg peak enhancement under ultrasound injection

社本真一*; 赤津光洋*; 松浦直人*; 河村聖子; 針井一哉*; 小野正雄*; Chang, L.-J.*; 伊藤孝; 根本祐一*; 家田淳一

Physical Review Research (Internet), 4(1), p.013245_1 - 013245_7, 2022/03

https://doi.org/10.1103/PhysRevResearch.4.013245

イットリウム鉄ガーネットの磁気ブラッグピークに対する超音波注入効果を、準弾性中性子散乱によって研究した。磁気ブラッグピークは、温度の低下とともに大幅に強化さる。エネルギー幅は、超音波注入によって引き起こされる試料温度上昇の平方根に比例して増加した。磁気ブラッグピークは格子振動によって増強されることから、この増強はスピン-格子結合と密接に関連していると予想される。縦波モードで100Kを超えると観測された急激な散乱信号の低下は、スピン-格子結合の劣化を示唆している。これは、温度が100Kを超えるとスピンゼーベック効果が低下することと一致しており、スピン-格子結合による劣化メカニズムに証明を与えている。

論文

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

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

https://doi.org/10.7566/JPSJ.90.073707

被引用回数：1 パーセンタイル：20.13(Physics, Multidisciplinary)

Ferromagnetic fluctuation relevant to the pressure-induced superconductivity in UGe 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

https://doi.org/10.1103/PhysRevB.103.155153

被引用回数：1 パーセンタイル：4.12(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 $_{1-x}$ RhGe ferromagnets in magnetic field along the axis

Pospil, 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, J.*; Sechovsk, V.*

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

https://doi.org/10.1103/PhysRevB.102.024442

被引用回数：7 パーセンタイル：32.39(Materials Science, Multidisciplinary)

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

論文

Structural characterization and magnetic behavior of uranium compound UPtAl $_{15}$

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

https://doi.org/10.7566/JPSCP.29.013003

Crystal structure and magnetic property of UPtAl $_{15}$ 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 (/3 /3 0), however, with a streak along the 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

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

https://doi.org/10.15669/pnst.5.123

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

Crystal structure and magnetic properties of new ternary uranium compound UTiBi

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

https://doi.org/10.15669/pnst.5.157

The crystal structure of the newly discovered compound UTiBi 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

Electronic states in EuCu(Ge $_{1-x}$ Si) 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

https://doi.org/10.7566/JPSJ.87.064706

被引用回数：20 パーセンタイル：71.93(Physics, Multidisciplinary)

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

論文

Anisotropic magnetic fluctuations in ferromagnetic superconductor UGe; $^{73}$ 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

https://doi.org/10.7566/JPSJ.87.033704

被引用回数：4 パーセンタイル：31.87(Physics, Multidisciplinary)

$^{73}$ Ge nuclear quadrupole resonance study of ferromagnetic superconductor UGe 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.

論文

Experimental observation of temperature and magnetic-field evolution of the 4 states in CeFe $_{2}$ revealed by soft X-ray magnetic circular dichroism

斎藤祐児; 保井晃*; 渕本寛人*; 中谷泰博*; 藤原秀紀*; 今田真*; 鳴海康雄*; 金道浩一*; 高橋稔*; 海老原孝雄*; et al.

Physical Review B, 96(3), p.035151_1 - 035151_5, 2017/07

AA2017-0611.pdf:0.36MB

https://doi.org/10.1103/PhysRevB.96.035151

被引用回数：4 パーセンタイル：19.29(Materials Science, Multidisciplinary)

単結晶CeFeを用い、X線吸収(XAS)磁気円2色性(XMCD)の高精度実験により、その強磁性的秩序相におけるCe4状態を調べた。Ce $M_{4,5}$ XMCDスペクトルは、温度及び磁場に依存した形状変化を示す一方、Ce $M_{4,5}$ XAS、Fe $L_{2,3}$ XAS及びXMCDスペクトルでは変化が観測されないという通常の強磁性体とは異なる現象が観測された。このような振る舞いは、Ce 4配置の基底状態と状態が混ざり合ったことに由来すると解釈できる。外部摂動に対し非常に敏感なCe 4状態は、本物質での強磁性相と反強磁相が隣接する磁気不安定性と関連付けることができる。我々の実験データは、混成の強い強磁性Ce化合物の物性に対して、貴重な情報を与える。

論文

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

https://doi.org/10.7566/JPSJ.86.044709

被引用回数：9 パーセンタイル：52.69(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.