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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：1 パーセンタイル：0(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

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：0 パーセンタイル：0(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

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：0 パーセンタイル：0(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

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：0 パーセンタイル：0(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：14 パーセンタイル：99.37(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：0 パーセンタイル：0(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：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

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：0 パーセンタイル：0(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.

論文

Charge-density-wave order and multiple magnetic transitions in divalent europium compound EuAl$$_4$$

金子 耕士; 川崎 卓郎; 仲村 愛*; 宗像 孝司*; 中尾 朗子*; 花島 隆泰*; 鬼柳 亮嗣; 大原 高志; 辺土 正人*; 仲間 隆男*; et al.

Journal of the Physical Society of Japan, 90(6), p.064704_1 - 064704_6, 2021/06

https://doi.org/10.7566/JPSJ.90.064704
 被引用回数：18 パーセンタイル：95.83(Physics, Multidisciplinary)

Multiple transition phenomena in divalent Eu compound EuAl$$_4$$ with the tetragonal structure were investigated via single crystal time-of-flight neutron Laue technique. At 30 K below a charge-density-wave (CDW) transition, superlattice peaks emerge near nuclear Bragg peaks described by an ordering vector $$q_{rm CDW}$$ = (0 0 $${delta}_c$$). In contrast, magnetic peaks appear at $$q_2 = ({delta}_2 {delta}_2 0)$$ with $${delta}_2$$ = 0.09 below $$T_{N1}$$ = 15.4 K, and moves to $$q_1 = ({delta}_1 0 0)$$ with $${delta}_1$$ = 0.19 below $$T_{N3}$$ =12.2 K, whereas no distinct change in the magnetic Bragg peak was detected at $$T_{N2}$$ and $$T_{N4}$$. The structural modification with $$q_{rm CDW}$$ is characterized by an absence of the superlattice peak in (0 0 $$l$$). Considering an absence of splitting in magnetic peaks along $$l$$, the structural transition is mainly ascribed to a displacement of Al ions within the tetragonal $$ab$$-plane. Complex incommensurate magnetic transitions are in stark contrast to a simple collinear commensurate structure in isovalent EuGa$$_4$$. This could stem from incompatible electronic structures with the CDW transition between two compounds.

論文

$$P$$2$$_1$$3の空間群に属する化合物および関連する化合物の結晶構造について

垣花 将司*; 竹内 徹也*; 芳賀 芳範; 播磨 尚朝*; 辺土 正人*; 仲間 隆男*; 大貫 惇睦*

固体物理, 55(10), p.505 - 514, 2020/10

立方晶キラル構造に属する磁性体が示す特異な磁気相が注目されている。代表的な物質MnSi(空間群$$P$$2$$_1$$3)および関連物質の構造の特徴を分類するとともに、一見複雑に見える結晶構造を安定化させる要因について考察する。

論文

4f電子系化合物EuPtSiで実現する磁気スキルミオン格子

金子 耕士; 垣花 将司*; 辺土 正人*; 仲間 隆男*; 大貫 惇睦*

波紋, 30(3), p.160 - 165, 2020/08

MnSiと同じ空間群に属する4$$f$$電子系化合物EuPtSiについて、磁気特性を調べた。単結晶中性子回折実験の結果、MnSiとEuPtSiの磁気構造に多くの共通点を見出した。この結果は、EuPtSiが4$$f$$電子系で初めて磁気スキルミオン格子を示す物質であることを示している。

論文

Electronic structure of trivalent compound EuPd$$_3$$ studied by soft X-ray angle-resolved photoemission spectroscopy

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

Journal of the Physical Society of Japan, 89(4), p.044704_1 - 044704_6, 2020/04

https://doi.org/10.7566/JPSJ.89.044704
 被引用回数：3 パーセンタイル：42.37(Physics, Multidisciplinary)

EuPd$$_3$$ is a rare Eu-based compound, whose Eu ions are in a trivalent state. The electronic structure of EuPd$$_3$$ was investigated by angle-resolved photoemission spectroscopy (ARPES) using soft X rays. Eu$$^{3+}$$ components arising from the 4f$$^5$$ final state multiplet were clearly observed in the valence spectra, and no Eu$$^{2+}$$ components were observed within an experimental accuracy, confirming a robust Eu$$^{3+}$$ state. The band structure and Fermi surfaces revealed by ARPES measurements were compared to the band structure calculations based on the density-functional theory for LaPd$$_3$$ andYPd$$_3$$. We found that the calculation for LaPd$$_3$$ provides a better description for our ARPES results. The effective electron masses estimated from the ARPES spectra near the Fermi level are in good agreement with the corresponding cyclotron effective masses in previous de Haas-van Alphen experiments.

論文

Quasi-one-dimensional magnetic interactions and conduction electrons in EuCu$$_5$$ and EuAu$$_5$$ with the characteristic hexagonal structure

松田 進弥*; 太田 譲二*; 仲井間 憲李*; 伊覇 航*; 郷地 順*; 上床 美也*; 中島 美帆*; 天児 寧*; 本多 史憲*; 青木 大*; et al.

Philosophical Magazine, 100(10), p.1244 - 1257, 2020/04

https://doi.org/10.1080/14786435.2019.1708498
 被引用回数：3 パーセンタイル：31.67(Materials Science, Multidisciplinary)

Single crystal samples of EuCu$$_5$$ and EuAu$$_5$$ have been successfully prepared. Using those samples, magnetic and electronic anisotropy has been clarified. Magnetic moment in the ferromagnetic state points to the hexagonal $$c$$-axis for both compounds. Electronic anisotropy was found in both electrical resistivity and Fermi surface topology. These anisotropic characteristics are accounted for by the unique hexagonal structure.

論文

Spin glass behavior in EuCu$$_2$$Si$$_2$$ single crystal grown by the flux method

竹内 徹也*; 芳賀 芳範; 谷口 年史*; 伊覇 航*; 安次富 洋介*; 屋良 朝之*; 木田 孝則*; 田原 大夢*; 萩原 政幸*; 中島 美帆*; et al.

Journal of the Physical Society of Japan, 89(3), p.034705_1 - 034705_15, 2020/03

https://doi.org/10.7566/JPSJ.89.034705
 被引用回数：0 パーセンタイル：0(Physics, Multidisciplinary)

Single crystals of EuCu$$_2$$Si$$_2$$ have been grown by the flux method and Bridgman method. The Eu ions of the Bridgman-grown crystal are nearly trivalent and fluctuate depending on the temperature. On the other hand, the Eu ions of flux-grown sample are divalent and thermally stable and show spin-glass behavior at low temperatures. Crystallographic analyses identified random replacement of Cu sites by Si only for the flux-grown samples. Such structural randomness leads to spin-glass features.

論文

Single crystal growth and unique electronic states of cubic chiral EuPtSi and related compounds

大貫 惇睦*; 垣花 将司*; 伊覇 航*; 仲井間 憲李*; 青木 大*; 仲村 愛*; 本多 史憲*; 中島 美帆*; 天児 寧*; 郷地 順*; et al.

JPS Conference Proceedings (Internet), 29, p.012001_1 - 012001_9, 2020/02

https://doi.org/10.7566/JPSCP.29.012001

EuPtSi with the cubic chiral structure exhibits a skyrmion phase under magnetic field. We succeeded in growing high-quality single crystals by the Bridgman method. Fermi surface splitting reflecting the noncentrosymmetric structure was successfully observed experimentally.

論文

4$$f$$電子系化合物EuPtSiにおける磁気スキルミオン

金子 耕士; 垣花 将司*; 辺土 正人*; 仲間 隆男*; 大貫 惇睦*

固体物理, 54(12), p.757 - 766, 2019/12

MnSiと同じ空間群に属する4$$f$$電子系化合物EuPtSiについて、磁気特性を調べた。単結晶中性子回折実験の結果、MnSiとEuPtSiの磁気構造に多くの共通点を見出した。この結果は、EuPtSiが4$$f$$電子系で初めて磁気スキルミオン格子を示す物質であることを示している。

論文

Magnetic field induced triple-$$q$$ magnetic order in trillium lattice antiferromagnet EuPtSi studied by resonant X-ray scattering

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

Journal of the Physical Society of Japan, 88(9), p.093704_1 - 093704_5, 2019/09

https://doi.org/10.7566/JPSJ.88.093704
 被引用回数：27 パーセンタイル：89.51(Physics, Multidisciplinary)

The magnetic order in the magnetic-fild-induced so-called A phase of cubic chiral antiferromagnet EuPtSi was investigated by resonant X-ray scattering (RXS) near the Eu $$L_{2}$$ edge. The high flux RXS signal under the magnetic field applied along [111] revealed the first and second order satellite magnetic reflections, indicating that the A phase is a triple-$$q$$ magnetic ordered state that is described by three propagation vectors lying in the plane normal to the magnetic field direction; $$q_1$$, $$q_2$$, and $$q_3$$. With the high resolution in the reciprocal space achieved in the RXS measurement, it is suggested that the triple-$$q$$ order strongly couples with the underlying crystal lattice. The triple-$$q$$ magnetic order is discussed in the context of a magnetic skyrmion lattice on which the geometrical frustration may play a crucial role.

論文

Electronic states of EuCu$$_2$$Ge$$_2$$ and EuCu$$_2$$Si$$_2$$ studied by soft X-ray photoemission spectroscopy

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

Physical Review B, 100(3), p.035111_1 - 035111_8, 2019/07

https://doi.org/10.1103/PhysRevB.100.035111
 被引用回数：7 パーセンタイル：48.15(Materials Science, Multidisciplinary)

We have carried out angle-integrated photoemission spectroscopy (AIPES) and angle-resolved photoemission spectroscopy (ARPES) experiments using soft X-rays on single crystals of EuCu$$_2$$Ge$$_2$$ and EuCu$$_2$$Si$$_2$$ grown by the Bridgman method to investigate their electronic structures. The AIPES results showed that the Eu ions in EuCu$$_2$$Ge$$_2$$ and EuCu$$_2$$Si$$_2$$ are in a divalent state and a nearly trivalent state, respectively, in accord with the previously reported magnetic properties. The three-dimensional band structures and shapes of the Fermi surfaces of EuCu$$_2$$Ge$$_2$$ and EuCu$$_2$$Si$$_2$$ were studied by ARPES measurements. We found that the band structures near the Fermi level and Fermi surfaces of EuCu$$_2$$Ge$$_2$$ and EuCu$$_2$$Si$$_2$$ are very different from each other and are well reproduced by the band structure calculations based on density-functional theory for SrCu$$_2$$Ge$$_2$$ and YCu$$_2$$Si$$_2$$. This suggests that a charge transfer from the localized 4$$f$$ states into the valence bands is responsible for the difference in the electronic states between EuCu$$_2$$Ge$$_2$$ and EuCu$$_2$$Si$$_2$$.

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

https://doi.org/10.1016/j.jallcom.2019.02.213
 被引用回数：2 パーセンタイル：16.98(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

Evidence for weak spin-orbit interaction experienced by Cooper pairs in the spin-triplet superconductor UPt$$_3$$; $$^{195}$$Pt-NMR study

青山 泰介*; 小手川 恒*; 木村 憲彰*; 山本 悦嗣; 芳賀 芳範; 大貫 惇睦*; 藤 秀樹*

Journal of the Physical Society of Japan, 88(6), p.064706_1 - 064706_7, 2019/06

https://doi.org/10.7566/JPSJ.88.064706
 被引用回数：0 パーセンタイル：0(Physics, Multidisciplinary)

$$^{195}$$Pt-NMR measurements under magnetic field ($$H$$) parallel to the $$c$$-axis in the vicinity of the upper critical field $$H_{rm c2}$$ have been carried out on the heavy-fermion superconductor UPt$$_3$$. The quasiparticle spin susceptibility was obtained from the measurements. The field dependence of the susceptibility suggests that the $$d$$-vector freely rotates in magnetic field. It is therefore concluded that spin-orbit interaction, which confines the direction of the $$d$$-vector with respect to the crystal axis, is weak in UPt$$_3$$.

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