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Your search keyword '"Ōnuki, Yoshichika"' showing total 524 results
Start Over Author "Ōnuki, Yoshichika" Publisher physical society of japan
524 results on '"Ōnuki, Yoshichika"'

2. 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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3. Field-induced Insulator–Metal Transition in EuTe2

Author

Takeuchi, Tetsuya, primary, Honda, Fuminori, additional, Aoki, Dai, additional, Haga, Yoshinori, additional, Kida, Takanori, additional, Narumi, Yasuo, additional, Hagiwara, Masayuki, additional, Kindo, Koichi, additional, Karube, Kosuke, additional, Harima, Hisatomo, additional, and Ōnuki, Yoshichika, additional

Published
2024
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4. 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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6. 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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9. Magnetic Properties of Single Crystalline Tb5Sb3

Author

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

Published
2023
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12. Cycloidal Magnetic Ordering in Noncentrosymmetric EuIrGe3

Author

Matsumura, Takeshi, primary, Tsukagoshi, Mitsuru, additional, Ueda, Yoshihisa, additional, Higa, Nonoka, additional, Nakao, Akiko, additional, Kaneko, Koji, additional, Kakihana, Masashi, additional, Hedo, Masato, additional, Nakama, Takao, additional, and Ōnuki, Yoshichika, additional

Published
2022
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17. 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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18. 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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19. Observation of Longitudinal Magnetic Fluctuations at a First-Order Ferromagnetic Quantum Phase Transition in UGe2

Author

Noma, Yuichiro, primary, Kotegawa, Hisashi, additional, Kubo, Tetsuro, additional, Tou, Hideki, additional, Harima, Hisatomo, additional, Haga, Yoshinori, additional, Yamamoto, Etsuji, additional, Ōnuki, Yoshichika, additional, Itoh, Kohei M., additional, Nakamura, Ai, additional, Homma, Yoshiya, additional, Honda, Fuminori, additional, and Aoki, Dai, additional

Published
2021
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22. 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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23. Magnetization Process in EuCo2P2 and EuT2Ge2 (T: transition metal): Comparison of Experiment and Theory

Author

Takeuchi, Tetsuya, primary, Tahara, Time, additional, Kida, Takanori, additional, Narumi, Yasuo, additional, Hagiwara, Masayuki, additional, Kindo, Koichi, additional, Iha, Wataru, additional, Ashitomi, Yousuke, additional, Yara, Tomoyuki, additional, Nakashima, Miho, additional, Amako, Yasushi, additional, Hedo, Masato, additional, Nakama, Takao, additional, and Ōnuki, Yoshichika, additional

Published
2021
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24. 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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30. Spin Glass Behavior in EuCu2Si2 Single Crystal Grown by the Flux Method

Author

Takeuchi, Tetsuya, primary, Haga, Yoshinori, additional, Taniguchi, Toshifumi, additional, Iha, Wataru, additional, Ashitomi, Yousuke, additional, Yara, Tomoyuki, additional, Kida, Takanori, additional, Tahara, Time, additional, Hagiwara, Masayuki, additional, Nakashima, Miho, additional, Amako, Yasushi, additional, Hedo, Masato, additional, Nakama, Takao, additional, and Ōnuki, Yoshichika, additional

Published
2020
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31. Charge-Density-Wave Order and Multiple Magnetic Transitions in Divalent Europium Compound EuAl4.

Author

Kaneko, Koji, Kawasaki, Takuro, Nakamura, Ai, Munakata, Koji, Nakao, Akiko, Hanashima, Takayasu, Kiyanagi, Ryoji, Ohhara, Takashi, Hedo, Masato, Nakama, Takao, and Ōnuki, Yoshichika

Abstract

Multiple transition phenomena in divalent Eu compound EuAl4 with the tetragonal structure were investigated via the single-crystal time-of-flight neutron Laue technique. At 30.0 K below a charge-density-wave (CDW) transition temperature of TCDW = 140 K, superlattice peaks emerge near nuclear Bragg peaks described by an ordering vector \(\boldsymbol{q}_{\text{CDW}} = (0,0,\delta _{c})\) with δc ∼ 0.19. In contrast, magnetic peaks appear at \(\boldsymbol{q}_{2} = (\delta _{2},\delta _{2},0)\) with δ2 = 0.085 in a magnetic-ordered phase at 13.5 K below TN1 = 15.4 K. By further cooling to below TN3 = 12.2 K, the magnetic ordering vector changes into \(\boldsymbol{q}_{1} = (\delta _{1},0,0)\) with δ1 = 0.17 at 11.5 K and slightly shifts to δ1 = 0.194 at 4.3 K. No distinct change in the magnetic Bragg peak was detected at TN2 = 13.2 K and TN4 = 10.0 K. The structural modulation below TCDW with qCDW is characterized by the absence of the superlattice peak in the (0 0 l) axis. As a similar CDW transition was observed in SrAl4, the structural modulation with qCDW could be mainly ascribed to the displacement of Al ions within the tetragonal ab-plane. Complex magnetic transitions are in stark contrast to a simple collinear magnetic structure in isovalent EuGa4. This could stem from different electronic structures with the CDW transition between two compounds. [ABSTRACT FROM AUTHOR]

Published
2021
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33. Magnetic Fluctuation and First-Order Transition in Trillium Lattice of EuPtSi Observed by 151Eu Mössbauer Spectroscopy

Author

Homma, Yoshiya, primary, Kakihana, Masashi, additional, Tokunaga, Yo, additional, Yogi, Mamoru, additional, Nakashima, Miho, additional, Nakamura, Ai, additional, Shimizu, Yusei, additional, Li, Dexin, additional, Maurya, Arvind, additional, Sato, Yoshiki J., additional, Honda, Fuminori, additional, Aoki, Dai, additional, Amako, Yasushi, additional, Hedo, Masato, additional, Nakama, Takao, additional, and Ōnuki, Yoshichika, additional

Published
2019
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41. De Haas–van Alphen Oscillations for Small Electron Pocket Fermi Surfaces and Huge H-linear Magnetoresistances in Degenerate Semiconductors PbTe and PbS

Author

Kawakatsu, Shoya, primary, Nakaima, Kenri, additional, Kakihana, Masashi, additional, Yamakawa, Yui, additional, Miyazato, Hayato, additional, Kida, Takanori, additional, Tahara, Time, additional, Hagiwara, Masayuki, additional, Takeuchi, Tetsuya, additional, Aoki, Dai, additional, Nakamura, Ai, additional, Tatetsu, Yasutomi, additional, Maehira, Takahiro, additional, Hedo, Masato, additional, Nakama, Takao, additional, and Ōnuki, Yoshichika, additional

Published
2019
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44. Electronic States of Antiferromagnet FeSn and Pauli Paramagnet CoSn

Author

Kakihana, Masashi, primary, Nishimura, Kengo, additional, Aoki, Dai, additional, Nakamura, Ai, additional, Nakashima, Miho, additional, Amako, Yasushi, additional, Takeuchi, Tetsuya, additional, Kida, Takanori, additional, Tahara, Time, additional, Hagiwara, Masayuki, additional, Harima, Hisatomo, additional, Hedo, Masato, additional, Nakama, Takao, additional, and Ōnuki, Yoshichika, additional

Published
2019
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45. Quantum Criticality of Valence Transition for the Unique Electronic State of Antiferromagnetic Compound EuCu2Ge2.

Author

Gouchi, Jun, Miyake, Kazumasa, Iha, Wataru, Hedo, Masato, Nakama, Takao, Ōnuki, Yoshichika, and Uwatoko, Yoshiya

Abstract

The effect of pressure on the unique electronic state of the antiferromagnetic (AF) compound EuCu2Ge2 has been measured in a wide temperature range from 10 mK to 300 K by electrical resistivity measurements up to 10 GPa. The Néel temperature of TN = 15 K at ambient pressure increases monotonically with increasing pressure and becomes a maximum of TN = 27 K at 6.2 GPa but suddenly drops to zero at \(P_{\text{c}} \simeq 6.5\) GPa, suggesting the quantum critical point (QCP) of the valence transition of Eu from a nearly divalent state to that with trivalent weight. The ρmag0 and A values obtained from the low-temperature electrical resistivity based on the Fermi liquid relation of ρmag = ρmag0 + AT2 exhibit huge and sharp peaks around Pc. The exponent n obtained from the power law dependence ρmag = ρmag0 + BTn is clearly less than 1.5 at \(P = P_{\text{c}} \simeq 6.5\) GPa, which is expected at the AF-QCP. These results indicate that Pc coincides with Pv, corresponding to the quantum criticality of the valence transition pressure Pv. The electronic specific heat coefficient γ, estimated from the generalized Kadowaki–Woods relation, is about 510 mJ/(mol·K2) around Pc, suggesting the formation of a heavy-fermion state. [ABSTRACT FROM AUTHOR]

Published
2020
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46. Electronic Structure of Trivalent Compound EuPd3 Studied by Soft X-ray Angle-resolved Photoemission Spectroscopy.

Author

Kawasaki, Ikuto, Kobata, Masaaki, Fujimori, Shin-ichi, Takeda, Yukiharu, Yamagami, Hiroshi, Nakamura, Ai, Iha, Wataru, Hedo, Masato, Nakama, Takao, and Ōnuki, Yoshichika

Abstract

EuPd3 is a rare Eu-based compound, whose Eu ions are in a trivalent state. The electronic structure of EuPd3 was investigated by angle-resolved photoemission spectroscopy (ARPES) using soft x rays. Eu3+ components arising from the 4f5 final state multiplet were clearly observed in the valence spectra, and no Eu2+ components were observed within experimental accuracy, confirming a robust Eu3+ state. The band structure and Fermi surfaces revealed by the ARPES measurements were compared to band structure calculations based on the density-functional theory for LaPd3 and YPd3. We found that the calculation for LaPd3 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. [ABSTRACT FROM AUTHOR]

Published
2020
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47. Spin Glass Behavior in EuCu2Si2 Single Crystal Grown by the Flux Method.

Author

Takeuchi, Tetsuya, Haga, Yoshinori, Taniguchi, Toshifumi, Iha, Wataru, Ashitomi, Yousuke, Yara, Tomoyuki, Kida, Takanori, Tahara, Time, Hagiwara, Masayuki, Nakashima, Miho, Amako, Yasushi, Hedo, Masato, Nakama, Takao, and Ōnuki, Yoshichika

Abstract

We grew single crystals of EuCu2Si2 by the Bridgman and In-flux methods, and studied their crystallographic and magnetic properties precisely to clarify the ground state at low temperatures. The Bridgman single crystals present almost the same magnetic properties as the previous arc-melted polycrystals, indicating a valence fluctuating state of the Eu ions. In the In-flux single crystals, the Eu ions are in the magnetic divalent state over the whole temperature range studied, and the system shows spin glass behavior below TSG = 11.5 K. From the crystallographic analyses, it is found that both the Bridgman and In-flux single crystals crystallize in the ThCr2Si2-type crystal structure, but in the In-flux crystals, a sizeable amount of Cu is replaced by Si, resulting in an off-stoichiometric composition. This replacement may cause the formation of random bonds for the magnetic exchange interactions, which leads to competing magnetic interactions and gives rise to spin glass features in the In-flux single crystals. [ABSTRACT FROM AUTHOR]

Published
2020
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50. Effects of Magnetic Field and Pressure on the Valence-Fluctuating Antiferromagnetic Compound EuPt2Si2

Author

Takeuchi, Tetsuya, primary, Yara, Tomoyuki, additional, Ashitomi, Yousuke, additional, Iha, Wataru, additional, Kakihana, Masashi, additional, Nakashima, Miho, additional, Amako, Yasushi, additional, Honda, Fuminori, additional, Homma, Yoshiya, additional, Aoki, Dai, additional, Uwatoko, Yoshiya, additional, Kida, Takanori, additional, Tahara, Time, additional, Hagiwara, Masayuki, additional, Haga, Yoshinori, additional, Hedo, Masato, additional, Nakama, Takao, additional, and Ōnuki, Yoshichika, additional

Published
2018
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