Browsing by Author "Hawai, T"

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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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    Temperature and composition phase diagram in the iron-based ladder compounds Ba1−xCsxFe2Se3
    (American Physical Society, 2015-05-28) Hawai, T; Nambu, Y; Ohgushi, K; Du, F; Hirata, Y; Avdeev, M; Uwatoko, Y; Sekine, Y; Fukazawa, H; Ma, J; Chi, S; Ueda, Y; Yoshizawa, H; Sato, TJ
    We investigated the iron-based ladder compounds (Ba,Cs)Fe2Se3. Their parent compounds BaFe2Se3 and CsFe2Se3 have different space groups, formal valences of Fe, and magnetic structures. Electrical resistivity, specific heat, magnetic susceptibility, x-ray diffraction, and powder neutron diffraction measurements were conducted to obtain a temperature and composition phase diagram of this system. Block magnetism observed in BaFe2Se3 is drastically suppressed with Cs doping. In contrast, stripe magnetism observed in CsFe2Se3 is not so fragile against Ba doping. A new type of magnetic structure appears in intermediate compositions, which is similar to stripe magnetism of CsFe2Se3, but interladder spin configuration is different. Intermediate compounds show insulating behavior, nevertheless a finite T-linear contribution in specific heat was obtained at low temperatures. ©2015 American Physical Society