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論文

Incommensurate helimagnetic structure of Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ determined by single-crystal neutron diffraction

田中誠也*; 鬼柳亮嗣; 石川喜久*; 天児寧*; 飯山拓*; 二村竜祐*; 丸山建一*; 内海重宣*

Physical Review Materials (Internet), 7(1), p.014403_1 - 014403_11, 2023/01

https://doi.org/10.1103/PhysRevMaterials.7.014403

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

Sc-substituted hexagonal ferrite Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ has an incommensurate helimagnetic structure. However, the incommensurate helimagnetic structure has not been sufficiently determined, and the mechanism via which the helimagnetism develops has not been studied. Time-of-flight single-crystal neutron diffraction measurements were performed on single-crystal samples of Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ with Sc concentrations of x = 0, 0.128, 0.153, and 0.193. The magnetic structure analyses revealed that the helimagnetic structure of Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ is a cone type whose base is in the ab plane and height is in the c-axis direction. The magnetic moments of Fe2(4), Fe4(4 $f_{2}$ ), and Fe5(12) are aligned with distinct angles, leading to the helimagnetic structure of Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ , and can be explained by assuming that there is an antiferromagnetic superexchange interaction $J_{5}$ between Fe2(4) and Fe5(12) that is negligible in the x = 0 crystal. The shorter bond distance of Fe2-O1 in Sc-rich crystals revealed by the crystal structure analyses enhances the superexchange interaction $J_{5}$ . The relatively strong $J_{5}$ leads to competition among the three superexchange interactions, $J_{3}$ , $J_{4}$ , and $J_{5}$ , resulting in the development of the helimagnetic structure. These findings facilitate the understanding of the essentials of the basic magnetic material BaFe $_{12}$ O $_{19}$ .

論文

Magnetic phase diagram of helimagnetic Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ (0 x 0.2) hexagonal ferrite

丸山建一*; 田中誠也*; 鬼柳亮嗣; 中尾朗子*; 森山健太郎*; 石川喜久*; 天児寧*; 飯山拓*; 二村竜祐*; 内海重宣*; et al.

Journal of Alloys and Compounds, 892, p.162125_1 - 162125_8, 2022/02

https://doi.org/10.1016/j.jallcom.2021.162125

被引用回数：2 パーセンタイル：16.86(Chemistry, Physical)

Hexagonal ferrite Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ is an important magnetic oxide material in both science and engineering because it exhibits helimagnetism around room temperature (300 K). In this study, the magnetic phase diagram of Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ consisting of ferri-, heli-, antiferro-, and paramagnetic phases has been completed through magnetization and neutron diffraction measurements. The magnetic phase transition temperature to paramagnetism decreases with the increase in x, and the temperature at which the magnetization reaches a maximum, which corresponds to the magnetic phase transition from heli- to ferrimagnetism, is determined for low x crystals. The temperatures at which helimagnetism appears are precisely determined by observing the magnetic satellite reflection peaks in neutron diffraction at various temperatures, which characterize helimagnetism. Based on these results, the magnetic phase diagram of the Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ system is constructed in the T-x plane. Helimagnetism appears at x 0.06, and magnetism with antiferromagnetic components appears as the extension phase of helimagnetism at x 0.19 through the coexistence region. The turn angle $phi_{0}$ of the helix for each x crystal is calculated from the relationship, $phi_{0} = 2pidelta$ , where is the incommensurability. The turn angle $phi_{0}$ decreases with the increase in temperature for the same x crystal, and increases with the increase in x at the same temperature. Furthermore, it is found that there are clear thresholds at which $phi_{0}$ cannot take values between 0 $^{circ}$ < $phi_{0}$ < 90 $^{circ}$ and 170 $^{circ}$ < $phi_{0}$ < 180 $^{circ}$ .

論文

Flux growth and magnetic properties of helimagnetic hexagonal ferrite Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ single crystals

内海重宣*; 田中誠也*; 丸山建一*; 天児寧*; 鬼柳亮嗣; 中尾朗子*; 森山健太郎*; 石川喜久*; 他9名*

ACS Omega (Internet), 5(38), p.24890 - 24897, 2020/09

https://doi.org/10.1021/acsomega.0c03671

被引用回数：4 パーセンタイル：21.18(Chemistry, Multidisciplinary)

六方晶フェライトBa(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ の磁気構造を解明し、さらなる応用開発を進めるためには、大型の高品質な単結晶を育成することが重要な第一歩である。本研究では、Na $_{2}$ O-Fe $_{2}$ O $_{3}$ フラックスを使用した自発結晶化法によって、さまざまなSc濃度のBa(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ 単結晶の育成に成功した。得られた結晶は、高品質の単相Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ であることがX線回折と元素分析により確認され、 = 0.128結晶の77Kの磁化測定では、ヘリマグネティックな挙動を示すことがわかった。=0.128結晶の中性子回折測定の結果、211K以下で磁気衛星反射が確認され、Ba(Fe $_{1-x}$ Sc $_{x}$ ) $_{12}$ O $_{19}$ がヘリ磁性物質であることが確認された。

論文

Quasi-one-dimensional magnetic interactions and conduction electrons in EuCu and EuAu 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：19.68(Materials Science, Multidisciplinary)

Single crystal samples of EuCu and EuAu have been successfully prepared. Using those samples, magnetic and electronic anisotropy has been clarified. Magnetic moment in the ferromagnetic state points to the hexagonal -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 EuCuSi 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 EuCuSi 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

Magnetic fluctuation and first-order transition in trillium lattice of EuPtSi observed by $^{151}$ Eu Mssbauer spectroscopy

本間佳哉*; 垣花将司*; 徳永陽; 與儀護*; 中島美帆*; 仲村愛*; 清水悠晴*; Li, D.*; Maurya, A.*; 佐藤芳樹*; et al.

Journal of the Physical Society of Japan, 88(9), p.094702_1 - 094702_8, 2019/08

https://doi.org/10.7566/JPSJ.88.094702

被引用回数：9 パーセンタイル：59.53(Physics, Multidisciplinary)

We report the results of $^{151}$ Eu Mssbauer spectroscopy on EuPtSi with a chiral structure belonging to the P2 $_{1}$ 3 space group at zero magnetic field. The paramagnetic single absorption forms a magnetic splitting profile directly below 4.0 K and the spectrum at 3.9 K consists of the sum of the paramagnetic single absorption and the magnetic splitting absorption, which indicates a first-order transition at 4.0 K. The temperature dependence of the effective hyperfine fields at the Eu nucleus follows a power law indicates a full moment of Eu $^{2+}$ ions.

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：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

Effects of magnetic field and pressure on the valence-fluctuating antiferromagnetic compound EuPtSi

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

https://doi.org/10.7566/JPSJ.87.074709

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 EuPtSi were studied using single-crystalline samples. Anomalous features in EuPtSi are due to valence fluctuation and/or valence change of the Eu ions at low temperatures.

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