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Your search keyword '"Takahiro Sakurai"' showing total 13 results
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13 results on '"Takahiro Sakurai"'

1. Pressure-tuned quantum criticality in the large-D antiferromagnet DTN

Author

Kirill Yu. Povarov, David E. Graf, Andreas Hauspurg, Sergei Zherlitsyn, Joachim Wosnitza, Takahiro Sakurai, Hitoshi Ohta, Shojiro Kimura, Hiroyuki Nojiri, V. Ovidiu Garlea, Andrey Zheludev, Armando Paduan-Filho, Michael Nicklas, and Sergei A. Zvyagin

Subjects
Science
Abstract

Abstract Strongly correlated spin systems can be driven to quantum critical points via various routes. In particular, gapped quantum antiferromagnets can undergo phase transitions into a magnetically ordered state with applied pressure or magnetic field, acting as tuning parameters. These transitions are characterized by z = 1 or z = 2 dynamical critical exponents, determined by the linear and quadratic low-energy dispersion of spin excitations, respectively. Employing high-frequency susceptibility and ultrasound techniques, we demonstrate that the tetragonal easy-plane quantum antiferromagnet NiCl2 ⋅ 4SC(NH2)2 (aka DTN) undergoes a spin-gap closure transition at about 4.2 kbar, resulting in a pressure-induced magnetic ordering. The studies are complemented by high-pressure-electron spin-resonance measurements confirming the proposed scenario. Powder neutron diffraction measurements revealed that no lattice distortion occurs at this pressure and the high spin symmetry is preserved, establishing DTN as a perfect platform to investigate z = 1 quantum critical phenomena. The experimental observations are supported by DMRG calculations, allowing us to quantitatively describe the pressure-driven evolution of critical fields and spin-Hamiltonian parameters in DTN.

Published
2024
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2. The Relationship Between Spin Crossover (SCO) Behaviors, Cation and Ligand Motions, and Intermolecular Interactions in a Series of Anionic SCO Fe(III) Complexes with Halogen-Substituted Azobisphenolate Ligands

Author

Mai Hirota, Suguru Murata, Takahiro Sakurai, Hitoshi Ohta, and Kazuyuki Takahashi

Subjects
spin crossover, Fe(III) complex, anionic complex, 2,2′-azobisphenolate ligand, halogen substituent effect, cooperativity, Organic chemistry, QD241-441
Abstract

To investigate the halogen substitution effect on the anionic spin crossover (SCO) complexes, azobisphenolate ligands with 5,5′-dihalogen substituents from fluorine to iodine were synthesized, and their anionic FeIII complexes 1F, 1Cl, 1Br, and 1I were isolated. The temperature dependence of magnetic susceptibility and crystal structure revealed that 1F, 1Cl, and 1Br are all isostructural and exhibit SCO with the rotational motion of the cation and ligands, whereas 1I shows incomplete SCO. Note that 1Cl and 1Br showed irreversible and reversible cooperative SCO transitions, respectively. Short intermolecular contacts between the FeIII complex anions were found despite Coulomb repulsions for all the complexes. The topological analysis of the electron density distributions revealed the existence of X···X halogen bonds, C–H···X, C–H···N, and C–H···O hydrogen bonds, and C–H···π interactions are evident. The dimensionality of intermolecular interactions is suggested to be responsible for the cooperative SCO transitions in 1Cl and 1Br, whereas the disorder due to the freezing of ligand rotations in 1Cl is revealed to inhibit the SCO cooperativity.

Published
2024
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4. One-dimensional stacking array of 10,20-diphenyl-5,15-diazaporphyrin metal complexes

Author

Shiho Mori, Takahiro Sakurai, Tsubasa Nishimura, Norihito Fukui, Yoshihiro Miyake, and Hiroshi Shinokubo

Subjects
General Chemistry
Abstract

We prepared a free-base 10,20-diphenyl-5,15-diazaporphyrin and its Ni(II), Cu(II), Pd(II), and Pt(II) complexes. These molecules uniformly form an infinite one-dimensional [Formula: see text]-stacking array in the solid state. The four-fold intermolecular hydrogen bonding interactions between the meso-nitrogen atom of the diazaporphyrin core and the ortho-hydrogen atom of the phenyl substituent dominate the crystal packing arrangement. The present study revealed that the meso-nitrogen atom of diazaporphyrins would be used as an inherent hydrogen bonding acceptor to construct supramolecular assemblies.

Published
2023
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5. Superconducting and Fermi Surface Properties of a Valence Fluctuation Compound CeIr2.

Author

Kazuyuki Omasa, Takuya Komoda, Yusuke Nakamura, Eiichi Matsuoka, Hisashi Kotegawa, Hideki Tou, Takahiro Sakurai, Hitoshi Ohta, Ai Nakamura, Yoshiya Homma, Dai Aoki, Daisuke Satoh, Mitsuhiro Yoshida, Sanu Mishra, Ilya Sheikin, Hisatomo Harima, and Hitoshi Sugawara

Abstract

CeIr2 was reported as a valence fluctuation compound with a superconducting transition temperature of ~0.3 K. To investigate its electronic and superconducting properties, we measured the electrical resistivity, magnetic susceptibility, and de Haas-van Alphen (dHvA) effect at low temperatures cooled to ~30mK and in high magnetic fields up to 36 T. The upper critical field (µ0Hc2 = 0.23 T) determined by the electrical resistivity under the magnetic field and the electron-phonon coupling constant (λep = 0.39) estimated from the Debye temperature suggested a weak-coupling BCStype superconductivity. The dHvA effect measurements mapped the Fermi surface in detail. The dHvA branches with the frequencies of F = 122-2180 T and the effective masses of m*c = 0:83{2:4m0 (m0: rest mass of an electron) were observed. These were reasonably explained by the band-structure calculation based on the full potential linearized augmented-plane-wave method within the local density approximation. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Modifiers of the Risk of Diabetes for Long-Term Outcomes After Coronary Revascularization

Author

Kyohei Yamaji, Hiroki Shiomi, Takeshi Morimoto, Yukiko Matsumura-Nakano, Natsuhiko Ehara, Hiroki Sakamoto, Yasuaki Takeji, Yusuke Yoshikawa, Ko Yamamoto, Eri T. Kato, Kazuaki Imada, Takeshi Tada, Ryoji Taniguchi, Ryusuke Nishikawa, Tomohisa Tada, Takashi Uegaito, Tatsuya Ogawa, Miho Yamada, Teruki Takeda, Hiroshi Eizawa, Nobushige Tamura, Keiichi Tambara, Satoru Suwa, Manabu Shirotani, Toshihiro Tamura, Moriaki Inoko, Junichiro Nishizawa, Masahiro Natsuaki, Hiroshi Sakai, Takashi Yamamoto, Naoki Kanemitsu, Nobuhisa Ohno, Katsuhisa Ishii, Akira Marui, Hiroshi Tsuneyoshi, Yasuhiko Terai, Shogo Nakayama, Kazuhiro Yamazaki, Mamoru Takahashi, Takashi Tamura, Jiro Esaki, Shinji Miki, Tomoya Onodera, Hiroshi Mabuchi, Yutaka Furukawa, Masaru Tanaka, Tatsuhiko Komiya, Yoshiharu Soga, Michiya Hanyu, Takenori Domei, Kenji Ando, Kazushige Kadota, Kenji Minatoya, Yoshihisa Nakagawa, Takeshi Kimura, Mitsuo Matsuda, Yuzo Takeuchi, Hirokazu Mitsuoka, Takashi Konishi, Seiji Ootani, Hisayoshi Fujiwara, Yoshiki Takatsu, Yukihito Sato, Kazuaki Kataoka, Ryuji Nohara, Kimisato Nakano, Syoichi Miyamoto, Nagai Kunihiko, Tomoyuki Murakami, Katsuya Ishida, Masakiyo Nobuyoshi, Hitoshi Yasumoto, Masashi Iwabuchi, Masayuki Kato, Ryozo Tatami, Ryuichi Hattori, Toru Kita, Yasuki Kihara, Hiroshi Kato, Takeshi Aoyama, Takahiro Sakurai, Masaki Kawanami, Tamaki Suyama, Eiji Tada, Tsukasa Inada, Hiroyasu Uzui, Akira Nakano, Jong-Dae Lee, Akinori Takizawa, Nawada Ryuzo, Eiji Shinoda, Masaaki Takahashi, Minoru Horie, Hiroyuki Takashima, Mamoru Toyofuku, Hajime Kotoura, Akira Miura, Yoshiki Matoba, Takuro Takumi, Chuwa Tei, Shuichi Hamasaki, Osamu Doi, Hirofumi Kambara, Satoshi Kaburagi, Kazuaki Mitsudo, Tetsu Mizoguchi, Yoshida Akira, Kazuhisa Kaneda, Hisao Ogawa, Koichi Sugamura, Seigo Sugiyama, Kiyoshi Doyama, Makoto Araki, Ryuzo Sakata, Tadashi Ikeda, Masahiko Onoe, Kazuo Yamanaka, Atsushi Iwakura, Keiichi Fujiwara, Kinji Soga, Tsutomu Matsushita, Noboru Nishiwaki, Yuichi Yoshida, Yukikatsu Okada, Michihiro Nasu, Tadaaki Koyama, Kuniyoshi Tanaka, Takaaki Koshiji, Koichi Morioka, Mitsuomi Shimamoto, Fumio Yamazaki, Masaki Aota, Hiroyuki Hara, Takafumi Tabata, Yutaka Imoto, Hiroyuki Yamamoto, Katsuhiko Matsuda, Masafumi Nara, Hiroyuki Nakajima, Michio Kawasuji, Syuji Moriyama, Sakiko Arimura, Yumika Fujino, Miya Hanazawa, Chikako Hibi, Risa Kato, Yui Kinoshita, Kumiko Kitagawa, Masayo Kitamura, Takahiro Kuwahara, Maeda Sachiko, Izumi Miki, Saeko Minematsu, Satoko Nishida, Naoko Okamoto, Asuka Saeki, Hitomi Sasae, Yuki Sato, Asuka Takahashi, Emi Takinami, Saori Tezuka, Marina Tsuda, Miyuki Tsumori, Yuriko Uchida, Yuko Yamamoto, Misato Yamauchi, Itsuki Yamazaki, Mai Yoshimoto, Mitsuru Abe, Masayuki Fuki, Mamoru Hayano, Eri Kato, Yoshihiro Kato, Tetsu Nakajima, Kenji Nakatsuma, Junichi Tazaki, Akihiro Tokushige, Hiroki Watanabe, Hidenori Yaku, Erika Yamamoto, and Yugo Yamashita

Published
2022
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9. Development of Pressure Calibration Method in High-Pressure THz ESR System

Author

Hitoshi Sugawara, Yoshimasa Yasutani, Susumu Okubo, Takahiro Sakurai, and Hitoshi Ohta

Subjects
Magnetization, Materials science, chemistry, Solid-state physics, Terahertz radiation, High pressure, Principal value, Calibration, Analytical chemistry, chemistry.chemical_element, Development (differential geometry), Tin, Atomic and Molecular Physics, and Optics
Abstract

We have developed a pressure calibration method in the high-pressure THz ESR system using induction coils set outside the pressure cell. The pressure is calibrated using alternating current (AC) magnetization measurements of the superconducting transition temperature of tin set inside the pressure cell with an ESR sample. The system fits the developed pressure cell with a wide frequency range of 0.05–0.8 THz. The pressure range was extended to 2.8 GPa. The ESR system was applied to the well-known cobalt Tutton’s salt $$({\text {NH}}_{4})_{2} {\rm {Co}}({\text {SO}}_{4})_{2}\cdot {\rm {6H}}_{2} {\text {O}}$$ , and its g principal values at 0 GPa were determined as $$g_{1}=6.61$$ , $$g_{2}=3.05$$ , and $$g_{3}=2.94$$ for the first time. Furthermore, we succeeded in observing the large change in these g values with pressure.

Published
2022

11. Impact of mixed anion ordered state on the magnetic ground states of S=1/2 square-lattice quantum spin antiferromagnets, Sr2NiO3Cl and Sr2NiO3F

Author

Yoshihiro Tsujimoto, Jun Sugiyama, Masayuki Ochi, Kazuhiko Kuroki, Pascal Manuel, Dmitry D. Khalyavin, Izumi Umegaki, Martin Månsson, Daniel Andreica, Shigeo Hara, Takahiro Sakurai, Susumu Okubo, Hitoshi Ohta, Andrew T. Boothroyd, and Kazunari Yamaura

Subjects
Physics and Astronomy (miscellaneous), General Materials Science
Published
2022
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