Browsing by Author "Ono, T"

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    Magnetic ordering of the buckled honeycomb lattice antiferromagnet Ba2NiTeO6
    (American Physical Society, 2016-01-19) Asai, S; Soda, M; Kasatani, K; Ono, T; Avdeev, M; Masuda, T
    We investigate the magnetic order of the buckled honeycomb lattice antiferromagnet Ba2NiTeO6 and its related antiferromagnet Ba3NiTa2O9 by neutron diffraction measurements. We observe magnetic Bragg peaks below the transition temperatures, and identify propagation vectors for these oxides. A combination of representation analysis and Rietveld refinement leads to a collinear magnetic order for Ba2NiTeO6 and a 120∘ structure for Ba3NiTa2O9. We find that the spin model of the bilayer triangular lattice is equivalent to that of the two-dimensional buckled honeycomb lattice having magnetic frustration. We discuss the magnetic interactions and single-ion anisotropy of Ni2+ ions for Ba2NiTeO6 in order to clarify the origin of the collinear magnetic structures. Our calculation suggests that the collinear magnetic order of Ba2NiTeO6 is induced by the magnetic frustration and easy-axis anisotropy. ©2016 American Physical Society
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    Stripy order in buckled honeycomb lattice antiferromagnet Ba2NiTeO6
    (International Conference on Neutron Scattering, 2017-07-12) Asai, S; Soda, M; Kasatani, K; Ono, T; Avdeev, M; Garlea, VO; Winn, B; Masuda, T
    Ba NiTeO is a rare experimental realization of a buckled honeycomb lattice antiferromagnet. The nearest-neighbor and next-nearest-neighbor interactions in the honeycomb lattice are comparative due to the buckled geometry, leading to magnetic frustration. A magnetic transition is observed at 8.6 K in the susceptibility and heat capacity measurements [1]. The frustration parameter /T is 18.6, where is Weiss temperature and is the magnetic transition temperature. In order to investigate the low temperature state we performed neutron scattering experiments. In the diffraction profile magnetic Bragg peaks are observed at < , and the propagation vector is identified as (0, 1/2,1). Combination of the representation analysis and Rietveld refinement reveals that a collinear stripy structure [2] is realized [3]. Our calculation suggests that the stabilization of the stripy structure instead of spiral structure is ascribed to the competition between magnetic frustration and easy-axis type anisotropy. In the inelastic neutron spectrum at 2 K a magnetic excitation with an energy gap of 2 meV is observed. Spin-wave calculation based on two-dimensional frustrated honeycomb lattice antiferromagnet having easy-axis anisotropy reproduces the experimental data. The obtained parameters are consistent with Weiss temperature estimated from the bulk magnetic susceptibility measurement.
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    Superconductivity in BaTi2Sb2O with a d1 square lattice
    (Physical Society of Japan, 2012-10-01) Yajima, T; Nakano, K; Takeiri, F; Ono, T; Hosokoshi, Y; Matsushita, Y; Hester, JR; Kobayashi, Y; Kageyama, H
    We prepared a new two-dimensional oxyantimonide, BaTi(2)Sb(2)O, which shows a superconducting transition at 1.2 K, representing the first superconductivity in a system with Ti(3+) (d(1)) in a square lattice. The TiO(2)Sb(4) mixed anionic coordination stabilizes a unique half-filled Ti d(xy) orbital configuration in Ti(2)O plane, which is analogous to Cu(2+) (d(9)) in the high-T(c) superconductors. A charge density wave (CDW)- or spin density wave (SDW)-like anomaly appears at 50 K, which is significantly reduced compared with 200 K for the isostructural and non-superconducting BaTi(2)As(2)O. © 2012, Physical Society of Japan