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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

 被引用回数:1 パーセンタイル:100(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

 被引用回数:1 パーセンタイル:100(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

 被引用回数:0 パーセンタイル:100(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

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

 被引用回数:4 パーセンタイル:30.92(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

 被引用回数:4 パーセンタイル:54.16(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

 被引用回数:2 パーセンタイル:49.74(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

Unique helical magnetic order and field-induced phase in trillium lattice antiferromagnet EuPtSi

金子 耕士; Frontzek, M. D.*; 松田 雅昌*; 中尾 朗子*; 宗像 孝司*; 大原 高志; 垣花 将司*; 芳賀 芳範; 辺土 正人*; 仲間 隆男*; et al.

Journal of the Physical Society of Japan, 88, p.013702_1 - 013702_5, 2019/01

 被引用回数:14 パーセンタイル:4.99(Physics, Multidisciplinary)

Magnetic transitions in chiral antiferromagnet EuPtSi were investigated by means of single crystal neutron diffraction. In the ground state, magnetic peaks emerge at positions represented by $$q_{1}$$=$$(0.2, 0.3, 0)$$. Upon heating, an additional magnetic peak splitting around 2.5 K was uncovered, indicating a presence of a first-order transition with $$q^*_{1}$$=$$(0.2, 0.3, {delta})$$. An half-polarized neutron scattering for polarization parallel to Q reveled that polarization antiparallel to Q has stronger intensity in both magnetic phases. This feature clarifies single chiral character of helical structure with moments normal to the ordering vector in both ordered states. Under vertical magnetic field along [1,1,1] in the $$A$$ phase, magnetic peaks form hexagonal patterns in the equatorial scattering plane around nuclear. An ordering vector $$q_{A}$$ of the $$A$$-phase has the similar size in the periodicity to $$q_{1}$$, and could be a hallmark of a formation of skyrmion lattice in EuPtSi.

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:6 パーセンタイル:34.54(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

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:11 パーセンタイル:20.58(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 $$x$$.

論文

Magnetic structure of divalent europium compound EuGa$$_{4}$$ studied by single-crystal time-of-flight neutron diffraction

川崎 卓郎; 金子 耕士; 仲村 愛*; 阿曽 尚文*; 辺土 正人*; 仲間 隆男*; 大原 高志; 鬼柳 亮嗣; 及川 健一; 田村 格良; et al.

Journal of the Physical Society of Japan, 85(11), p.114711_1 - 114711_5, 2016/11

 被引用回数:3 パーセンタイル:61.66(Physics, Multidisciplinary)

The magnetic structure of the intermetallic compound EuGa$$_{4}$$ was investigated using single-crystal neutron diffraction with TOF Laue technique on the new diffractometer SENJU at MLF of J-PARC. Despite of the high neutron absorption of Eu, a vast number of diffraction spots were observed without isotope enrichment. The magnetic reflections appeared at $$h + k + l$$ $$neq$$ 2$$n$$ below 16 K, indicating that the ordering vector is $$q$$ = (0, 0, 0). The continuous evolution of the magnetic reflection intensity below T$$_{N}$$ follows a squared Brillouin function for $$S$$ = 7/2. By adopting a wavelength-dependent absorption collection, the magnetic structure of EuGa$$_{4}$$ revealed that a nearly full magnetic moment of 6.4 $$mu$$B of Eu lies within the basal plane of the lattice.

論文

Electronic structure of EuAl$$_4$$ studied by photoelectron spectroscopy

小畠 雅明; 藤森 伸一; 竹田 幸治; 岡根 哲夫; 斎藤 祐児; 小林 啓介*; 山上 浩志; 仲村 愛*; 辺土 正人*; 仲間 隆男*; et al.

Journal of the Physical Society of Japan, 85(9), p.094703_1 - 094703_6, 2016/09

 被引用回数:5 パーセンタイル:53.75(Physics, Multidisciplinary)

The electronic structure of a divalent $$mathrm{Eu}$$ compound EuAl$$_4$$, which shows the charge density wave transition at $$T_{mathrm{CDW}} = 140~mathrm{K}$$, was studied by the hard X-ray angle-integrated photoelectron spectroscopy (HAXPES) and the soft X-ray angle resolved photoelectron spectroscopy (ARPES). The valence band and core-level spectra obtained by the HAXPES are consistent with the divalent nature of Eu atoms in EuAl$$_4$$. Furthermore, the Fermi surface as well as the band structure in the vicinity of the Fermi Energy ($$E_{rm F}$$) of EuAl$$_4$$ are very similar to those of its isostructural divalent $$mathrm{Sr}$$ compound SrAl$$_4$$, which does not have $$4f$$ electrons. These suggest that Eu atoms are divalent in EuAl$$_4$$, and $$4f$$ electrons are completely localized with $$mathrm{Eu}~4f^7$$ electronic configuration in the ground state. The ARPES spectra measured along the $$Gamma$$-$$(Sigma)$$-Z high-symmetry line did not show significant temperature dependences above and below $$T_{mathrm{CDW}}$$ within the energy resolution of $$80-90~mathrm{meV}$$. Moreover, the Fermi surface mapping along the $$k_z$$ direction showed that both of EuAl$$_4$$ and SrAl$$_4$$ have highly three-dimensional electronic structures, suggesting that the nesting of Fermi surface is not straightforward. The Fermi surface and band structure of SrAl$$_4$$ were well explained by the band-structure calculation based on the local density approximation.

論文

Superconducting and Fermi surface properties of single crystal Zr$$_2$$Co

照屋 淳志*; 垣花 将司*; 竹内 徹也*; 青木 大*; 本多 史憲*; 仲村 愛*; 芳賀 芳範; 松林 和幸*; 上床 美也*; 播磨 尚朝*; et al.

Journal of the Physical Society of Japan, 85(3), p.034706_1 - 034706_10, 2016/03

 被引用回数:0 パーセンタイル:100(Physics, Multidisciplinary)

Superconducting characteristics and Fermi surfaces of Zr$$_2$$Co are experimentally studied on a single crystal sample grown by Bridgman technique. Thermodynamic quantities in the superconducting state such as specific heat and magnetization show deviation from a single-gap the BCS model and can be attributed on the band structure with the dominant contribution of Zr-4$$d$$ and Co-3$$d$$ components.

論文

Split Fermi surface properties in Ulmannite NiSbS and PdBiSe with the cubic chiral crystal structure

垣花 将司*; 照屋 淳志*; 西村 憲吾*; 仲村 愛*; 竹内 徹也*; 芳賀 芳範; 播磨 尚朝*; 辺土 正人*; 仲間 隆男*; 大貫 惇睦

Journal of the Physical Society of Japan, 84(9), p.094711_1 - 094711_8, 2015/09

 被引用回数:13 パーセンタイル:28.16(Physics, Multidisciplinary)

Fermi surface properties of illuminate NiSbS and PbBiSe have been clarified by de Haas-van Alphen effect, resistivity and specific heat measurements. Fermi surfaces were found to split into two, reflecting the non-centrosymmetric crystal structure. The splitting energies have been estimated experimentally. Those are originated from spin-orbit interactions.

論文

Characteristic fermi surface properties of V$$_2$$Ga$$_5$$, CoGa$$_3$$, TiGa$$_3$$, ZrGa$$_3$$, and ZrAl$$_3$$ with different tetragonal structures

照屋 淳志*; 竹田 政貴*; 仲村 愛*; 播磨 尚朝*; 芳賀 芳範; 内間 清春*; 辺土 正人*; 仲間 隆男*; 大貫 惇睦*

Journal of the Physical Society of Japan, 84(5), p.054703_1 - 054703_15, 2015/05

 被引用回数:3 パーセンタイル:64.03(Physics, Multidisciplinary)

A series of metallic compounds with the tetragonal symmetry are investigated to reveal the relationship between the structural dimensionality and the electronic structure. By combining the de Haas-van Alphen experiments and band structure calculations, a flat one-dimensional Fermi surface is revealed in V$$_2$$Ga$$_5$$ which is characterized by a chain like arrangement of atoms. On the other hand, Co$$_3$$Ga with the nearly cubic symmetry has pyramidal Fermi surfaces with flat {111} planes, similar to Ni$$_3$$Ga with the ideal cubic structure.

論文

Unique Fermi surface and emergence of charge density wave in EuGa$$_4$$ and EuAl$$_4$$

仲村 愛*; 平仲 裕一*; 辺土 正人*; 仲間 隆男*; 三浦 泰直*; 堤 泰樹*; 森 晶宣*; 石田 一裕*; 三田村 勝哉*; 広瀬 雄介*; et al.

JPS Conference Proceedings (Internet), 3, p.011012_1 - 011012_6, 2014/06

Two europium compounds with the same structure EuGa$$_4$$ and EuAl$$_4$$ have been investigated. The Fermi surfaces revealed experimentally show a peculiar feature: flat Fermi surface sheets appear parallel to the tetragonal [110] planes. Reflecting this, a charge density wave transition due to the nesting of Fermi surface sheets has been observed in EuAl$$_4$$.

論文

Single crystal neutron diffraction study of high neutron absorbing compound EuGa$$_{4}$$

川崎 卓郎; 金子 耕士; 阿曽 尚文*; 仲村 愛*; 辺土 正人*; 仲間 隆男*; 大貫 惇睦*; 大原 高志; 鬼柳 亮嗣; 及川 健一; et al.

JPS Conference Proceedings (Internet), 1, p.014009_1 - 014009_4, 2014/03

Single crystal neutron diffraction measurement of EuGa$$_{4}$$ has been carried out using time-of-flight single crystal neutron diffractometer SENJU at BL18 in MLF/J-PARC. In spite of extremely high neutron absorption of natural Eu, significant numbers of Bragg reflection were observed. Lattice parameters and Bravais lattice at above $$T_mathrm{N}$$ (=15 K) obtained from the positions and systematic extinction of the reflections were well agreed with the result of single crystal X-ray diffraction. Further, magnetic reflections were clearly observed at below $$T_mathrm{N}$$ at the positions of forbidden reflections of body-centered lattice of EuGa$$_{4}$$. An antiferromagnetic structure with the propagation vector $$q$$ = 0 was clarified.

論文

Fermi surface and magnetic properties of antiferromagnet EuBi$$_3$$

仲村 愛*; 平仲 裕一*; 辺土 正人*; 仲間 隆男*; 立津 慶幸*; 眞榮平 孝裕*; 三浦 泰直*; 森 晶宣*; 堤 泰樹*; 広瀬 雄介*; et al.

Journal of the Physical Society of Japan, 82(12), p.124708_1 - 124708_6, 2013/12

 被引用回数:17 パーセンタイル:27.4(Physics, Multidisciplinary)

Fermi surfaces and magnetic properties of an antiferromagnet EuBi$$_3$$ were investigated on a flux-grown single crystal. A critical magnetic field of 225 kOe where the magnetic moments are forced to align ferromagnetically was well explained by the magnetic exchange interaction based on a two-sublattice model. The Fermi surface characteristics are in agreement with the theoretical prediction indicating a fully magnetic divalent state in Eu atoms.

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