Browsing by Author "Mitsuda, S"

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    Gapless spin liquid in a square-kagome lattice antiferromagnet
    (Springer Nature Limited, 2020-06-09) Fujihala, M; Morita, K; Mole, RA; Mitsuda, S; Tohyama, T; Yano, SI; Yu, DH; Sota, S; Kuwai, T; Koda, A; Okabe, H; Lee, H; Itoh, H; Hawai, T; Masuda, T; Sagayama, H; Matsuo, A; Kindo, K; Ohira-Kawamura, S; Nakajima, K
    Observation of a quantum spin liquid (QSL) state is one of the most important goals in condensed-matter physics, as well as the development of new spintronic devices that support next-generation industries. The QSL in two dimensional quantum spin systems is expected to be due to geometrical magnetic frustration, and thus a kagome-based lattice is the most probable playground for QSL. Here, we report the first experimental results of the QSL state on a square-kagome quantum antiferromagnet, KCu6AlBiO4(SO4)5Cl. Comprehensive experimental studies via magnetic susceptibility, magnetisation, heat capacity, muon spin relaxation (μSR), and inelastic neutron scattering (INS) measurements reveal the formation of a gapless QSL at very low temperatures close to the ground state. The QSL behavior cannot be explained fully by a frustrated Heisenberg model with nearest-neighbor exchange interactions, providing a theoretical challenge to unveil the nature of the QSL state. © 2020 Springer Nature Limited
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    Relief of spin frustration through magnetic anisotropy in the quasi-one-dimensional 𝑆= 1/2 antiferromagnet Na2⁢CuSO4⁢Cl2
    (American Physical Society (APS), 2022-03-29) Fujihala, M; Sakuma, Y; Mitsuda, S; Nakao, A; Munakata, K; Mole, RA; Yano, S; Yu, DH; Takehana, K; Imanaka, Y; Akaki, M; Okubo, S; Ohta, H
    We report the magnetic structure and anisotropy of the quasi-one-dimensional S=12 antiferromagnet Na2CuSO4Cl2 obtained by single-crystal neutron scattering, electron spin resonance (ESR), and magnetization measurements, following an earlier study of its dynamics [M. Fujihala, Phys. Rev. B 101, 024410 (2020)10.1103/PhysRevB.101.024410]. A Néel-Type spin structure is formed within the chain of this compound, where the spins point along the b axis, and ESR data indicate an antisymmetric exchange with a uniform Dzyaloshinskii-Moriya (DM) vector pointing along the b axis. The anisotropy g factor and magnetic structure are strong indicators of magnetic anisotropy originating from a symmetric anisotropic exchange interaction and/or a magnetic dipole interaction. These results suggest that these terms of the anisotropic spin Hamiltonian counteract the effect of the DM interaction and stabilize the Néel-Type structure in Na2CuSO4Cl2. ©2022 American Physical Society.
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    Spin dynamics and magnetic ordering in the quasi-one-dimensional S=12 antiferromagnet Na2CuSO4Cl2
    (American Physical Society (APS), 2020-01-01) Fujihala, M; Mitsuda, S; Mole, RA; Yu, DH; Watanabe, I; Yano, S; Kuwai, T; Sagayama, H; Kouchi, T; Kamebuchi, H; Tadokoro, M
    The S=12 quasi-one-dimensional antiferromagnet K2CuSO4X2(X=Cl, Br) exhibits peculiar Dzyaloshinskii-Moriya (DM) interactions that are uniform along its spin chains and antiparallel with respect to neighboring chains. This feature has received much attention recently because it leads to spin frustration, however, the spin dynamics around TN and magnetic structure have not been reported. Here we report magnetic behaviors of Na2CuSO4Cl2. The orthorhombic crystal structure of Na2CuSO4Cl2, which is identical to K2CuSO4X2, was verified. The results of the thermodynamic measurements suggest that this compound has moderately strong intra- and interchain interaction for investigation of the spin state around TN. The inelastic neutron scattering and muon spin relaxation and rotation measurements reveal the presence of a two-spinon continuum, and below TN, the long-range order develops. However, the obtained critical exponent is β=0.18, which is not indicative of a three-dimensional magnetic system; instead, one-dimensional (1D) spin correlation likely affects the formation of magnetic ordering in Na2CuSO4Cl2. There is a possibility that Na2CuSO4Cl2 is a model compound for investigation of DM-induced frustration effects in a 1D quantum spin system. ©2024 American Physical Society. All rights reserved.