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232 results on '"Ōnuki, Yoshichika"'

1. Distorted triangular skyrmion lattice in a noncentrosymmetric tetragonal magnet

Author

Matsumura, Takeshi, Kurauchi, Kenshin, Tsukagoshi, Mitsuru, Higa, Nonoka, Nakao, Hironori, Kakihana, Masashi, Hedo, Masato, Nakama, Takao, and Ōnuki, Yoshichika

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

Magnetic skyrmions are particle-like spin-swirling objects ubiquitously realized in magnets. They are topologically stable chiral kinks composed of multiple modulation waves of spiral spin structures, where the helicity of each spiral is usually selected by antisymmetric exchange interactions in noncentrosymmetric crystals. We report an experimental observation of a distorted triangular lattice of skyrmions in the polar tetragonal magnet EuNiGe$_3$, reflecting a strong coupling with the lattice. Moreover, through resonant x-ray diffraction, we find that the magnetic helicity of the original spiral at zero field is reversed when the skyrmion lattice is formed in a magnetic field. This means that the energy gain provided by the skyrmion lattice formation is larger than the antisymmetric exchange interaction. Our findings will lead us to a further understanding of emergent magnetic states., Comment: 9 pages, 3 figures, supplemental material (6 pages, 12 figures)

Published
2023
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2. Non-coplanar helimagnetism in the layered van-der-Waals metal DyTe$_3$

Author

Akatsuka, Shun, Esser, Sebastian, Okumura, Shun, Yambe, Ryota, Yamada, Rinsuke, Hirschmann, Moritz M., Aji, Seno, White, Jonathan S., Gao, Shang, Onuki, Yoshichika, Arima, Taka-hisa, Nakajima, Taro, and Hirschberger, Max

Subjects
Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons
Abstract

Magnetic materials with highly anisotropic chemical bonding can be exfoliated to realize ultrathin sheets or interfaces with highly controllable optical or spintronics responses, while also promising novel cross-correlation phenomena between electric polarization and the magnetic texture. The vast majority of these van-der-Waals magnets are collinear ferro-, ferri-, or antiferromagnets, with a particular scarcity of lattice-incommensurate helimagnets of defined left- or right-handed rotation sense, or helicity. Here we use polarized neutron scattering to reveal cycloidal, or conical, magnetic structures in DyTe$_3$, with coupled commensurate and incommensurate order parameters, where covalently bonded double-slabs of dysprosium square nets are separated by highly metallic tellurium layers. Based on this ground state and its evolution in a magnetic field as probed by small-angle neutron scattering (SANS), we establish a one-dimensional spin model with off-diagonal on-site terms, spatially modulated by the unconventional charge order in DyTe$_3$. The CDW-driven term couples to antiferromagnetism, or to the net magnetization in applied magnetic field, and creates a complex magnetic phase diagram indicative of competing interactions in an easily cleavable helimagnet. Our work paves the way for twistronics research, where helimagnetic layers can be combined to form complex spin textures on-demand, using the vast family of rare earth chalcogenides and beyond., Comment: 61 pages, 5 figures, 16 extended figures

Published
2023
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6. Single Crystal Growth and Electronic Properties of RGa6 (R: Rare Earth Metals).

Author

Afzal, Md Asif, Higashinaka, Ryuji, Imai, Yuki, Nakamura, Naoki, Nakachi, Ryu, Ōnuki, Yoshichika, Arima, Hiroto, Yamashita, Aichi, Mizuguchi, Yoshikazu, Aoki, Dai, Harima, Hisatomo, Aoki, Yuji, and Matsuda, Tatsuma D.

Abstract

We succeeded in growing high-quality single crystals of RGa6 (R: rare earth metals from Y to Ho except Eu) with the PuGa6-type tetragonal structure by the Ga-self flux method, and measured the electrical resistivity, specific heat, magnetic susceptibility, and magnetization, together with the de Haas–van Alphen (dHvA) experiment for SmGa6. All the magnetic RGa6 compounds order antiferromagnetically and the corresponding magnetic easy-axes are mainly directed along the [001] direction, except CeGa6 and SmGa6. Characteristic metamagnetic transitions were observed in PrGa6, NdGa6, TbGa6, DyGa6, and HoGa6 in the magnetization curves. The main Fermi surface of SmGa6 was detected in the dHvA experiment, with a cyclotron effective mass of about 1 m0 (m0: rest mass of an electron), revealing an antiferromagnet with a localized magnetic moment of Sm3+. [ABSTRACT FROM AUTHOR]

Published
2024
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7. Helicity Unification by Triangular Skyrmion Lattice Formation in the Noncentrosymmetric Tetragonal Magnet EuNiGe3.

Author

Matsumura, Takeshi, Kurauchi, Kenshin, Tsukagoshi, Mitsuru, Higa, Nonoka, Nakao, Hironori, Kakihana, Masashi, Hedo, Masato, Nakama, Takao, and Ōnuki, Yoshichika

Abstract

Magnetic skyrmions are particle-like spin-swirling objects ubiquitously realized in magnets. They are topologically stable chiral kink structures composed of multiple modulation waves of spiral spin structures. The helicity of each spiral is usually determined by antisymmetric exchange interactions in noncentrosymmetric crystals. We report an experimental observation of a distorted triangular lattice of skyrmions in the polar tetragonal magnet EuNiGe3 in a magnetic field, reflecting a strong coupling with the lattice. Moreover, through circularly polarized resonant X-ray diffraction on Bragg peaks from four separate magnetic domains, we discovered a change in the magnetic helicity of the original spiral at zero field when the skyrmion lattice is formed with a unified helicity of the three q components. This implies that the energy gain provided by the skyrmion lattice formation is larger than the antisymmetric exchange interaction. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Anomalous ferromagnetic ordering in EuCuP

Author

Iha, Wataru, Kakihana, Masashi, Matsuda, Shinya, Honda, Fuminori, Haga, Yoshinori, Takeuchi, Tetsuya, Nakashima, Miho, Amako, Yasushi, Gouchi, Jun, Uwatoko, Yoshiya, Hedo, Masato, Nakama, Takao, and Ōnuki, Yoshichika

Published
2019
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11. Enhanced emergent electromagnetic inductance in Tb5Sb3 due to highly disordered helimagnetism.

Author

Kitaori, Aki, White, Jonathan S., Ukleev, Victor, Peng, Licong, Nakajima, Kiyomi, Kanazawa, Naoya, Yu, Xiuzhen, Ōnuki, Yoshichika, and Tokura, Yoshinori

Subjects
ELECTRIC inductance, ELECTROMAGNETIC induction, SMALL-angle neutron scattering, SMALL-angle scattering, ELECTRICAL resistivity, CONDUCTION electrons, ELECTRIC fields
Abstract

In helimagnetic metals, ac current-driven spin motions can generate emergent electric fields acting on conduction electrons, leading to emergent electromagnetic induction (EEMI). Recent experiments reveal the EEMI signal generally shows a strongly current-nonlinear response. In this study, we investigate the EEMI of Tb5Sb3, a short-period helimagnet. Using small angle neutron scattering we show that Tb5Sb3 hosts highly disordered helimagnetism with a distribution of spin-helix periodicity. The current-nonlinear dynamics of the disordered spin helix in Tb5Sb3 indeed shows up as the nonlinear electrical resistivity (real part of ac resistivity), and even more clearly as a nonlinear and huge EEMI (imaginary part of ac resistivity) response. The magnitude of the EEMI reaches as large as several tens of μH for Tb5Sb3 devices on the scale of several tens of μm, originating to noncollinear spin textures possibly even without long-range helimagnetic order. Ac current-driven spin motions in helimagnetic metals can generate emergent electric fields acting on conduction electrons, leading to emergent electromagnetic induction (EEMI). In this study, we revealed that a short-period helimagnet Tb5Sb3 may have disordered spin helix structure and provides large EEMI. [ABSTRACT FROM AUTHOR]

Published
2024
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12. Large Cyclotron Effective Masses in Antiferromagnet SmTi2Al20 Compared with Conventional Masses in Ferromagnet SmNi2Cd20 and Antiferromagnet SmPd2Cd20.

Author

Afzal, Md Asif, Ōnuki, Yoshichika, Aoki, Dai, Harima, Hisatomo, Higashinaka, Ryuji, Aoki, Yuji, and Matsuda, Tatsuma D.

Abstract

We grew high-quality single crystals of a ferromagnet SmNi2Cd20, an antiferromagnet SmPd2Cd20, and an antiferromagnet SmTi2Al20 with the cubic cage structure by the self-flux method and carried out the de Haas–van Alphen experiment to detect the large cyclotron effective masses of the main Fermi surfaces. This is because these compounds are reported to possess large electronic specific heat coefficients of 100–200 mJ/(K2·mol). We have succeeded in detecting the main Fermi surfaces. The corresponding cyclotron mass of a so-called valence-fluctuating compound SmTi2Al20 is surprisingly large, revealing 26 m0 (m0: rest mass of an electron). In SmTi2Al20, no Curie–Weiss term is found in the magnetic susceptibility, and the −log T dependence of the electrical resistivity is observed at low temperatures. On the other hand, the conventional masses of 2.1 m0 are obtained in SmNi2Cd20 and SmPd2Cd20, following the Curie–Weiss law in the magnetic susceptibility. [ABSTRACT FROM AUTHOR]

Published
2024
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15. Superconducting, Fermi surface, and magnetic properties in SrTGe3 and EuTGe3 (T: transition metal) with the Rashba-type tetragonal structure

Author

Kakihana, Masashi, Akamine, Hiromu, Tomori, Keisuke, Nishimura, Kengo, Teruya, Atsushi, Nakamura, Ai, Honda, Fuminori, Aoki, Dai, Nakashima, Miho, Amako, Yasushi, Matsubayashi, Kazuyuki, Uwatoko, Yoshiya, Takeuchi, Tetsuya, Kida, Takanori, Hagiwara, Masayuki, Haga, Yoshinori, Yamamoto, Etsuji, Harima, Hisatomo, Hedo, Masato, Nakama, Takao, and Ōnuki, Yoshichika

Published
2017
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19. Studies of 27Al NMR in SrAl4

Author

Niki, Haruo, Higa, Nonoka, Kuroshima, Hiroko, Toji, Tatsuki, Morishima, Mach, Minei, Motofumi, Yogi, Mamoru, Nakamura, Ai, Hedo, Masato, Nakama, Takao, Ōnuki, Yoshichika, and Harima, Hisatomo

Published
2015
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20. Unique Electronic States in Non-centrosymmetric Cubic Compounds

Author

Kakihana, Masashi, Nishimura, Kengo, Ashitomi, Yousuke, Yara, Tomoyuki, Aoki, Dai, Nakamura, Ai, Honda, Fuminori, Nakashima, Miho, Amako, Yasushi, Uwatoko, Yoshiya, Sakakibara, Toshiro, Nakamura, Shota, Takeuchi, Tetsuya, Haga, Yoshinori, Yamamoto, Etsuji, Harima, Hisatomo, Hedo, Masato, Nakama, Takao, and Ōnuki, Yoshichika

Published
2017
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22. Single Crystal Growth and Characterization of Tetragonal EuIr4In2Ge4 with Dresselhaus-type Spin–Orbit Coupling.

Author

Nakachi, Ryu, Sugiyama, Shinya, Ōnuki, Yoshichika, Homma, Yoshiya, Li, DeXin, Aoki, Dai, Harima, Hisatomo, Higashinaka, Ryuji, Aoki, Yuji, and Matsuda, Tatsuma D.

Abstract

In the process of growing single crystals of EuIr2Ge2 with the ThCr2Si2-type tetragonal structure via the In-flux method, we obtained single crystals of EuIr4In2Ge4 in which Dresselhaus spin–orbit coupling can be expected. We present the details of single crystal growth for EuIr2Ge2 and EuIr4In2Ge4 and the magnetic properties of EuIr4In2Ge4 with a Néel temperature 2.5 K. [ABSTRACT FROM AUTHOR]

Published
2024
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23. Magnetic Properties of Single Crystalline Tb5Sb3.

Author

Kitaori, Aki, Kanazawa, Naoya, Kida, Takanori, Narumi, Yasuo, Hagiwara, Masayuki, Kindo, Koichi, Takeuchi, Tetsuya, Nakamura, Ai, Aoki, Dai, Haga, Yoshinori, Kaneko, Yoshio, Tokura, Yoshinori, and Ōnuki, Yoshichika

Abstract

We have successfully grown single crystalline Tb5Sb3 with the hexagonal structure, which was reported to exhibit successive transitions among complex spiral magnetic structures with changing temperature. Through the measurements of specific heat and magnetization of the single crystalline Tb5Sb3, we have identified only one clear magnetic transition at 133 K. The ordered moments are approximately oriented in the hexagonal basal plane, while the hard axis of magnetization corresponds to the [0001] direction. This magnetic structure with the ferromagnetic-like order is transformed below 50 K, resulting in a rapid decrease in the magnetic susceptibility for \(H\parallel [10\bar{1}0]\) and a kink behavior in a low-field magnetization, although the nearly ferromagnetic state continues below 50 K, revealing a hysteresis in the magnetization curve. [ABSTRACT FROM AUTHOR]

Published
2023
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32. Split Fermi Surface Properties of Noncentrosymmetric Compounds Fe2P, Ni2P, and Pd2Si.

Author

Ōnuki, Yoshichika, Nakamura, Ai, Aoki, Dai, Matsuda, Tatsuma D., Haga, Yoshinori, Harima, Hisatomo, Takeuchi, Tetsuya, and Kaneko, Yoshio

Abstract

We grew single crystals of Fe2P, Ni2P, and Pd2Si with a noncentrosymmetric Fe2P-type hexagonal structure, studied their Fermi surface properties by de Haas–van Alphen (dHvA) experiments, and compared results with energy band calculations. In paramagnets Ni2P and Pd2Si, the detected dHvA branches are well explained by the results of full potential linear augmented plane wave (FLAPW) band calculations. Because of the noncentrosymmetric crystal structure, the energy band splits, leading to two split Fermi surfaces. The angular dependences of dHvA frequencies for the main split Fermi surfaces are highly anisotropic, which is not observed for \(H\parallel [0001]\) but observed for \(H\perp [0001]\). The splitting energy due to the antisymmetric spin–orbit coupling is approximately estimated to be Δε \(\simeq \) 300 K in Ni2P and 500 K in Pd2Si for \(H\parallel [10\bar{1}0]\). This is a characteristic feature of the split Fermi surfaces in these compounds. In the case of a ferromagnet Fe2P, only one kind of spin-split dHvA branch was observed. [ABSTRACT FROM AUTHOR]

Published
2022
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37. Abrupt Change in Electronic States under Pressure in New Compound EuPt3Al5.

Author

Koizumi, Takatsugu, Honda, Fuminori, Sato, Yoshiki J., Li, Dexin, Aoki, Dai, Haga, Yoshinori, Gouchi, Jun, Nagasaki, Shoko, Uwatoko, Yoshiya, Kaneko, Yoshio, and Ōnuki, Yoshichika

Abstract

We successfully grew single crystals of a new ternary Eu-divalent compound, EuPt3Al5, with an orthorhombic structure (Pnma, #62) using the Bridgman method. EuPt3Al5 orders antiferromagnetically below TN = 12.4 K. TN increases monotonically with increasing pressure up to 8.0 GPa, decreases slightly at 8.5 GPa, and suddenly becomes zero above 9.5 GPa. From the results of low-temperature dependences of electrical and residual resistivities, a sudden disappearance of the antiferromagnetic ordering occurs with a dramatic change in the Eu electronic states from the nearly divalent state to the valence fluctuating state at Pc ≈ 9 GPa. EuPt3Al5 is most likely the second material exhibiting an abrupt valence crossover in Eu compounds after EuCu2Ge2. [ABSTRACT FROM AUTHOR]

Published
2022
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