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論文

Revisiting $$^{9}$$Be nuclear magnetic resonance in UBe$$_{13}$$; Itinerant-localized duality and possible Fermi surface reconstruction at high magnetic field

松木 麟太朗*; 南 晶子*; 小手川 恒*; 播磨 尚朝*; 芳賀 芳範; 山本 悦嗣; 大貫 惇睦*; 藤 秀樹*

Journal of the Physical Society of Japan, 94(12), p.124702_1 - 124702_8, 2025/11

https://doi.org/10.7566/JPSJ.94.124702
 被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

We report on new results of $$^{9}$$Be nuclear magnetic resonance measurements conducted on a single crystal of the heavy fermion superconductor UBe$$_{13}$$. A comparison between the knight shift and the classical dipolar shift provides microscopic evidence for the nature of an itinerant-localized duality in UBe$$_{13}$$. Furthermore, a reconstruction of part of the multiple Fermi surfaces in the high-magnetic-field region is suggested.

論文

Influence of magnetic ordering on quasiparticle spectral functions; Comparison of electronic states of CeCu$$_6$$ and CeRu$$_2$$Ge$$_2$$

川崎 郁斗; 藤森 伸一; 山上 浩志; 松田 達磨*; 大貫 惇睦*

Journal of the Physical Society of Japan, 94(8), p.084702_1 - 084702_9, 2025/07

https://doi.org/10.7566/JPSJ.94.084702
 被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

The electronic state of CeCu$$_6$$, an archetypical heavy compound without long-range magnetic order, has been investigated by angle-resolved photoemission spectroscopy (ARPES) experiments using soft X rays. The Ce 3$$d$$-4$$f$$ resonant ARPES experiments have revealed the 4$$f$$ partial density of states consists of a quasiparticle band near the Fermi level ($$f^1$$ component) and an $$f^0$$ component, the latter of which is physically equivalent to the lower Hubbard band in the Hubbard model. The observed strong intensity of the $$f^0$$ component indicates that the quasiparticle band near the Fermi level is strongly renormalized by the electron correlation effect, consistent with the significantly enhanced electronic specific-heat coefficient of CeCu$$_6$$. We compare the present 3$$d$$-4$$f$$ resonant ARPES spectra of CeCu$$_6$$ with those for CeRu$$_2$$Ge$$_2$$, which has a low Kondo temperature similar to CeCu$$_6$$ but shows a ferromagnetic order. The results of this comparison suggest that the ferromagnetic correlation in CeRu$$_2$$Ge$$_2$$ seems to strongly suppress the degree of renormalization for the quasiparticle band. We also showed that the intensities of both the $$f^1$$ and $$f^0$$ components for CeCu$$_6$$ hardly depend on temperature.

論文

Giant Hall effect in a highly conductive frustrated magnet GdCu$$_{2}$$

軽部 皓介*; 大貫 惇睦*; 中島 多朗*; Chen, H.-Y.*; 石塚 大晃*; 木俣 基*; 大原 高志; 宗像 孝司*; 野本 拓也*; 有田 亮太郎*; et al.

npj Quantum Materials (Internet), 10, p.55_1 - 55_9, 2025/06

https://doi.org/10.1038/s41535-025-00774-3
 被引用回数：6 パーセンタイル：87.77(Materials Science, Multidisciplinary)

The Hall effect is one of the most fundamental but elusive phenomena in condensed matter physics due to the rich variety of underlying mechanisms. Here we report an exceptionally large Hall effect in a frustrated magnet, GdCu$$_{2}$$, with high conductivity. The Hall conductivity at the base temperature shows abrupt sign changes under magnetic fields. Our systematic measurements indicate that the unusual Hall effect can be understood in terms of spin-splitting-induced emergence/disappearance of Fermi pockets as well as skew scattering from spin-chiral cluster fluctuations in a field-polarized state. The present study demonstrates a complex interplay among magnetization, spin-dependent electronic structure, and spin fluctuations in producing the giant Hall effect in highly conductive frustrated magnets with a distorted triangular lattice.

論文

Two-dimensional Dresselhaus-type spin texture and nonreciprocal magnetoresistance in magnetic semiconductor EuIr$$_4$$In$$_2$$Ge$$_4$$

横山 旭*; 仲地 立*; 本間 佳哉*; 仲村 愛*; 清水 悠晴*; Li, D.*; 三宅 厚志*; 本多 史憲*; 青木 大*; 大貫 惇睦*; et al.

Journal of the Physical Society of Japan, 94(2), p.023701_1 - 023701_4, 2025/02

https://doi.org/10.7566/JPSJ.94.023701
 被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)

We present the nonreciprocal magnetoresistance (NRMR) and spin texture of the noncentrosymmetric magnetic semiconductor EuIr$$_4$$In$$_2$$Ge$$_4$$. Anisotropy measurements of NRMR for different crystalline axes under rotational magnetic fields revealed a two-dimensional Dresselhaus-type spin texture of this material, where the spin polarization is confined to the tetragonal (001) plane. Strong coupling between NRMR and magnetism was suggested by the low-temperature field dependence of NRMR; however, the magnitude of NRMR was more rapidly suppressed by increasing the temperature than that of magnetic susceptibility. This distinct behavior implies extra mechanisms to reduce the NRMR in addition to the reduction of magnetic moment due to the temperature increase.

論文

Single helicity of the triple-$$q$$ triangular skyrmion lattice state in the cubic chiral helimagnet EuPtSi

松村 武*; 田端 千紘; 金子 耕士; 中尾 裕則*; 垣花 将司*; 辺土 正人*; 仲間 隆男*; 大貫 惇睦*

Physical Review B, 109(17), p.174437_1 - 174437_8, 2024/05

https://doi.org/10.1103/PhysRevB.109.174437
 被引用回数：10 パーセンタイル：77.83(Materials Science, Multidisciplinary)

We investigated the magnetic helicity of the triple-$$q$$ magnetic structure of the triangular skyrmion lattice in the A-phase of EuPtSi for a magnetic field along the [111] axis by resonant X-ray diffraction using a circularly polarized beam. We show that all three Fourier components of the triple-$$q$$ structure are perpendicular to the respective $$q$$ vectors and have the same helicity. They are connected by the rotation operations about the [111] axis. The helicity is the same as that of the single-$$q$$ helimagnetic phase at low fields, suggesting that the antisymmetric exchange interaction inherent in the chiral structure supports the formation of the triangular skyrmion lattice. We also observe that the helical plane in the helimagnetic phase is tilted to the magnetic field to form a conical structure before the first-order transition to the skyrmion lattice phase.

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

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$$_2$$ 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

Magnetic and fermi surface properties of semimetals EuAs$$_3$$ and Eu(As$$_{1-x}$$P$$_x$$)$$_3$$

大貫 惇睦*; 軽部 皓介*; 青木 大*; 仲村 愛*; 本間 佳哉*; 松田 達磨*; 芳賀 芳範; 竹内 徹也*

Journal of the Physical Society of Japan, 92(11), p.114703_1 - 114703_12, 2023/11

https://doi.org/10.7566/JPSJ.92.114703
 被引用回数：1 パーセンタイル：15.68(Physics, Multidisciplinary)

Single crystal samples of a series of semimetallic magnet Eu(As$$_{1-x}$$P$$_x$$)$$_3$$ have successfully grown. By measuring magnetization, Hall resistivity and de Haas-van Alphen oscillations, large anomalous Hall resistivity arising from peculiar magnetic phase diagram was identified.

論文

Incommensurate nature of the antiferromagnetic order in GdCu$$_2$$

金子 耕士; 田端 千紘; 萩原 雅人; 山内 宏樹; 久保田 正人; 長壁 豊隆; 大貫 惇睦*

Journal of the Physical Society of Japan, 92(8), p.085001_1 - 085001_2, 2023/08

https://doi.org/10.7566/JPSJ.92.085001
 被引用回数：1 パーセンタイル：15.68(Physics, Multidisciplinary)

A magnetic order in orthorhombic GdCu$$_2$$ was investigated by a single crystal neutron diffraction with thermal neutron. Magnetic peaks were observed at incommensurate positions described by the ordering vector $$q$$=($${delta}$$~1~0) with $${delta}$$=0.678 at 4~K. This ordering vector is close to the commensurate one with $$q_c$$=(2/3~1~0) reported earlier, but clearly deviates. The incommensurate nature of the magnetic order in GdCu$$_2$$ is further corroborated by the peak shift with temperature below $$T_{rm N}$$.

論文

Quasiparticle state in 4$$f$$ localized ferromagnet CeRu$$_2$$Ge$$_2$$ studied by soft X-ray photoemission spectroscopy

川崎 郁斗; 藤森 伸一; 竹田 幸治; 山上 浩志; 大貫 惇睦*

Journal of the Physical Society of Japan, 92(6), p.064709_1 - 064709_8, 2023/06

https://doi.org/10.7566/JPSJ.92.064709
 被引用回数：1 パーセンタイル：15.68(Physics, Multidisciplinary)

The electronic state of 4$$f$$ localized ferromagnet CeRu$$_2$$Ge$$_2$$ has been investigated by angle-resolved photoemission spectroscopy (APRES) experiments using soft X rays. The band structure and Fermi surfaces consisting of non-4$$f$$ bands are almost consistent with a calculation based on the density-functional theory for LaRu$$_2$$Ge$$_2$$, thus confirming a localized character of the 4$$f$$ electrons. On the other hand, the Ce 3$$d$$-4$$f$$ resonant ARPES experiments demonstrated that the 4$$f$$ spectral function is dominated by $$f^{1}$$ components in the vicinity of the Fermi level and thus is different from that expected for a localized electron system. We also revealed that the intensities of the $$f^{1}$$ components have almost no temperature dependence up to at least 100 K, which is two orders of magnitude larger than the Kondo temperature of CeRu$$_2$$Ge$$_2$$.

論文

Magnetic properties of single crystalline Tb$$_5$$Sb$$_3$$

北折 暁*; 金澤 直也*; 木田 孝則*; 鳴海 康雄*; 萩原 政幸*; 金道 浩一*; 竹内 徹也*; 仲村 愛*; 青木 大*; 芳賀 芳範; et al.

Journal of the Physical Society of Japan, 92(2), p.024702_1 - 024702_6, 2023/02

https://doi.org/10.7566/JPSJ.92.024702
 被引用回数：2 パーセンタイル：29.01(Physics, Multidisciplinary)

Magnetic properties of Tb$$_5$$Sb$$_3$$ are reported. Unlike previous investigations on a polycrystal showing multiple phase transitions, the present single crystal sample shows a single transition 133 K. It is also shown that the magnetic hysteresis increases at low temperatures.

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

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

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

Cycloidal magnetic ordering in noncentrosymmetric EuIrGe$$_3$$

松村 武*; 塚越 舜*; 上田 祥央*; 比嘉 野乃花*; 中尾 朗子*; 金子 耕士; 垣花 将司*; 辺土 正人*; 仲間 隆男*; 大貫 惇睦*

Journal of the Physical Society of Japan, 91(7), p.073703_1 - 073703_5, 2022/07

https://doi.org/10.7566/JPSJ.91.073703
 被引用回数：9 パーセンタイル：64.25(Physics, Multidisciplinary)

Successive magnetic phase transitions in EuIrGe$$_3$$, an intermetallic compound with a body centered tetragonal lattice belonging to a polar space group I4mm, has been investigated by neutron diffraction and resonant X-ray diffraction. It is shown that EuIrGe$$_3$$ exhibits an incommensurate longitudinal sinusoidalorder with $$q{sim}$$ (0, 0, 0.792) and m$$_q{parallel}$$ c-axis in the high temperature phase, which changes to a cycloidal order with $$q$$ = ($${delta}'$$, 0, 0.8) ($${delta}'{sim}$$ 0.017) and m$$_q{parallel}$$ ac-plane in the intermediate phase. In the low temperature phase, the cycloidal plane rotates by 45$$^{circ}$$ to have $$q$$=($${delta}, {delta}$$, 0.8) ($${delta}{sim}$$0.012). It is also pointed out that the X-ray scattering amplitude from odd-parity magnetic quadrupole due to the polar environment interfere with that from normal even-parity magnetic dipole in the magnetic ordered phase.

論文

Split Fermi surface properties of noncentrosymmetric compounds Fe$$_2$$P, Ni$$_2$$P, and Pd$$_2$$Si

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

Journal of the Physical Society of Japan, 91(6), p.064712_1 - 064712_10, 2022/06

https://doi.org/10.7566/JPSJ.91.064712
 被引用回数：3 パーセンタイル：32.14(Physics, Multidisciplinary)

Fermi surface of noncentrocymmetric Fe$$_2$$P, Ni$$_2$$P and Pd$$_2$$Si was studied by means of de Haas-van Alphen experiments. The splitting energy of Fermi surfaces due to antisymmetric spin-orbit coupling is estimated.

論文

Single crystal growth and magnetic properties of $$alpha$$-Mn and $$beta$$-Mn

大貫 惇睦*; 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.065001_1 - 065001_2, 2022/06

https://doi.org/10.7566/JPSJ.91.065001
 被引用回数：2 パーセンタイル：23.15(Physics, Multidisciplinary)

Single crystals of $$alpha$$-Mn and $$beta$$-Mn are successfully grown. Non-Fermi-liquid relations of the low-temperature resistivity and specific heat are found in the spin-liquid state of $$beta$$-Mn. On the other hand, $$alpha$$-Mn exhibits antiferromagnetic transition.

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

https://doi.org/10.7566/JPSJ.91.065002
 被引用回数：3 パーセンタイル：32.14(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

https://doi.org/10.7566/JPSJ.91.043704
 被引用回数：7 パーセンタイル：56.79(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

Square and rhombic lattices of magnetic skyrmions in a centrosymmetric binary compound

高木 里奈*; 松山 直文*; Ukleev, V.*; Yu, L.*; White, J. S.*; Francoual, S.*; Mardegan, J. R. L.*; 速水 賢*; 齋藤 開*; 金子 耕士; et al.

Nature Communications (Internet), 13, p.1472_1 - 1472_7, 2022/03

https://doi.org/10.1038/s41467-022-29131-9
 被引用回数：143 パーセンタイル：99.55(Multidisciplinary Sciences)

Magnetic skyrmions are topologically stable swirling spin textures with particle-like character, and have been intensively studied as a candidate of high-density information bit. While magnetic skyrmions were originally discovered in noncentrosymmetric systems, recently a nanometric skyrmion lattice has also been reported for centrosymmetric rare-earth compounds. For the latter systems, a novel skyrmion formation mechanism mediated by itinerant electrons has been proposed, and the search of a simpler model system allowing for a better understanding of their intricate magnetic phase diagram is highly demanded. Here, we report the discovery of square and rhombic lattices of nanometric skyrmions in a centrosymmetric binary compound EuAl$$_4$$, by performing small-angle neutron and resonant elastic X-ray scattering experiments. Unlike previously reported centrosymmetric skyrmion-hosting materials, EuAl$$_4$$ shows multiple-step reorientation of the fundamental magnetic modulation vector as a function of magnetic field, probably reflecting a delicate balance of associated itinerant-electron-mediated interactions. The present results demonstrate that a variety of distinctive skyrmion orders can be derived even in a simple centrosymmetric binary compound, which highlights rare-earth intermetallic systems as a promising platform to realize/control the competition of multiple topological magnetic phases in a single material.

論文

Electronic structure of the intermediate-valence compound EuNi$$_2$$P$$_2$$ studied by soft X-ray photoemission spectroscopy

川崎 郁斗; 小畠 雅明; 藤森 伸一; 竹田 幸治; 山上 浩志; 辺土 正人*; 仲間 隆男*; 大貫 惇睦*

Physical Review B, 104(16), p.165124_1 - 165124_8, 2021/10

https://doi.org/10.1103/PhysRevB.104.165124
 被引用回数：1 パーセンタイル：3.77(Materials Science, Multidisciplinary)

We carried out angle-resolved photoemission (ARPES) experiments using soft X rays to investigate the electronic structure of the intermediate valence compound EuNi$$_2$$P$$_2$$. Both the Eu$$^{2+}$$ and Eu$$^{3+}$$ components arising from the 4$$f^6$$ and 4$$f^5$$ final states were observed in the valence spectra, directly confirming an intermediate character of Eu ions. The three-dimensional band structure was studied by ARPES measurements, and we found that the ARPES spectra up to just below the Fermi level can well be explained by a calculation based on the density-functional theory for the non-4$$f$$ reference compound SrNi$$_2$$P$$_2$$. The heavy-fermion bands in EuNi$$_2$$P$$_2$$ are thus considered to be formed through the hybridization between the dispersive valence bands, which resemble those for SrNi$$_2$$P$$_2$$, and the Eu$$^{2+}$$ components located at the very vicinity of the Fermi level.

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

https://doi.org/10.7566/JPSJ.90.073707
 被引用回数：2 パーセンタイル：19.01(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

Critical slowing-down and field-dependent paramagnetic fluctuations in the skyrmion host EuPtSi; $$mu$$SR and NMR studies

比嘉 野乃花*; 伊藤 孝; 與儀 護*; 服部 泰佑; 酒井 宏典; 神戸 振作; Guguchia, Z.*; 髭本 亘; 中島 美帆*; 本間 佳哉*; et al.

Physical Review B, 104(4), p.045145_1 - 045145_7, 2021/07

https://doi.org/10.1103/PhysRevB.104.045145
 被引用回数：6 パーセンタイル：30.30(Materials Science, Multidisciplinary)

We report the results of $$mu$$SR and $$^{29}$$Si NMR measurements carried out on the cubic chiral magnet EuPtSi. Our zero-field $$mu$$SR experiments revealed the development of critical slowing down of Eu spin fluctuations over a relatively wide critical region above $$T_N$$. We also found from $$^{29}$$Si NMR that the spin fluctuations are strongly suppressed by magnetic field in the paramagnetic state above 20K. These characteristic spin dynamics observed over a wide region of temperature and magnetic field suggest the presence of magnetic frustration in the spin system. Such frustration would underlie the mechanism stabilizing the short-period skyrmion lattice observed in this compound.

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