Browsing by Author "Kindo, K"

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    Field-induced ferromagnetism of Fe4+-perovskite system, Sr(1-x)BaxFeO3 (0 ≤x≤1)
    (The Physical Society of Japan, 2013-09-05) Hayashi, N; Yamamoto, T; Kitada, A; Matsuo, A; Kindo, K; Hester, JR; Kageyama, H; Takano, M
    A series of cubic perovskite-type oxides, Sr1-xBaxFe4+O3 (0≤x≤1 ), have been studied through measurements of neutron diffraction and magnetization. It has been found that their helical spin structure changes from the G-type to the A-type with increasing Ba content at x∼0.85 . The application of an external magnetic field induces ferromagnetism with ∼3.5 µB/Fe, and the strength of the critical field decreases markedly from 39 T for SrFeO3 to 0.3 T for BaFeO3. The transition process can be categorized into three: SrFeO3, Sr0.4Ba0.6FeO3, and BaFeO3 types. © 2013 The Physical Society of Japan
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    Frustrated magnetism in the J1−J2 honeycomb lattice compounds MgMnO3 and ZnMnO3 synthesized via a metathesis reaction
    (American Physical Society, 2019-12-17) Haraguchi, Y; Nawa, K; Michioka, C; Ueda, J; Matsuo, A; Kindo, K; Avdeev, M; Sato, TJ; Yoshimura, K
    We investigated the magnetic properties of the ilmenite-type manganates MgMnO3 and ZnMnO3, both of which are composed of a honeycomb lattice of magnetic Mn4+ ions. Both compounds show antiferromagnetic order with weak ferromagnetic moments. In particular, MgMnO3 exhibits a magnetization “reversal” behavior which can be described by the N-type ferrimagnetism in the Néel's classification. The relationship between the magnetic properties and the crystal and magnetic structures probed by the neutron diffraction experiments indicates that the two honeycomb lattice magnets have different J1−J2 parameter sets, placing them in the distinct regions in the phase diagram; both nearest neighbor (NN) and next nearest neighbor (NNN) exchange interactions are antiferromagnetic in MgMnO3, while NN and NNN interactions become ferromagnetic and antiferromagnet, respectively, in ZnMnO3. ©2019 American Physical Society
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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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    Quantum magnetic properties of the spin-1/2 triangular-lattice antiferromagnet Ba2La2CoTe2O12
    (American Physical Society, 2018-11-05) Kojima, Y; Watanabe, M; Kurita, N; Tanaka, H; Matsuo, A; Kindo, K; Avdeev, M
    We report the crystal structure of Ba2La2CoTe2O12 determined by Rietveld analysis using x-ray powder-diffraction data. It was found from magnetic measurements that Ba2La2CoTe2O12 can be described as a spin-12 triangular-lattice antiferromagnet with easy-plane anisotropy at low temperatures. This compound undergoes a magnetic phase transition at TN=3.26K to an ordered state with the 120∘ structure. The magnetization curve exhibits the one-third plateau characteristic of triangular-lattice quantum antiferromagnets. The antiferromagnetic exchange interaction and the g factors parallel and perpendicular to the c axis were evaluated to be J/kB=22K,g∥=3.5, and g⊥=4.5, respectively. ©2018 American Physical Society
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    Successive phase transitions and magnetization plateau in the spin-1 triangular-lattice antiferromagnet Ba2La2NiTe2O12 with small easy-axis anisotropy
    (American Physical Society, 2019-08-22) Saito, M; Watanabe, M; Kurita, N; Matsuo, A; Kindo, K; Avdeev, M; Jeschke, HO; Tanaka, H
    The crystal structure and magnetic properties of the spin-1 triangular-lattice antiferromagnet Ba2La2NiTe2O12 are reported. Its crystal structure is trigonal R¯3, which is the same as that of Ba2La2NiW2O12 [Y. Doi et al., J. Phys.: Condens. Matter 29, 365802 (2017)]. However, the exchange interaction J/kB≃19 K is much greater than that observed in the tungsten system. At zero magnetic field, Ba2La2NiTe2O12 undergoes successive magnetic phase transitions at TN1=9.8 K and TN2=8.9 K. The ground state is accompanied by a weak ferromagnetic moment. These results indicate that the ground-state spin structure is a triangular structure in a plane perpendicular to the triangular lattice owing to the small easy-axis-type anisotropy. The magnetization curve exhibits the one-third plateau characteristic of a two-dimensional triangular-lattice Heisenberg-like antiferromagnet. Exchange constants are also evaluated using density functional theory (DFT). The DFT results demonstrate the large difference in the exchange constants between tellurium and tungsten systems and the good two-dimensionality of the tellurium system. ©2019 American Physical Society