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### Browsing by Author "Soda, M"

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- ItemMagnetic order in frustrated Kagome-Triangular lattice antiferromagnet NaBa2Mn3F11(American Physical Society, 2017-03) Hayashida, S; Ishikawa, H; Okamoto, Y; Okubo, T; Hiroi, Z; Avdeev, M; Manuel, P; Hagihala, M; Soda, M; Masuda, T
Show more We performed powder neutron diffraction experiments on NaBa2Mn3F11 [1], a model compound of \textit{Kagome-Triangular} lattice where three of six next-nearest neighbor interactions are non-negligible. More than 10 magnetic Bragg peaks are clearly observed below T= 2 K, meaning that the ground state is a magnetically ordered state. From indexing the magnetic Bragg peaks, magnetic propagation vector of \textbf{\textit{q}}0= (0, 0, 0) and two incommensurate vectors which are close to (1/3, 1/3, 0) are identified. Combination of representation analysis and Rietveld refinement reveals that the propagation vector of \textbf{\textit{q}}0 exhibits the 120º structure in the \textit{ab}-plane. Our calculation of the ground state suggests that the non-negligible magnetic dipolar interaction is responsible for the determined 120º structure in NaBa2Mn3F11. © 2021 American Physical SocietyShow more - ItemMagnetic 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
Show more 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 SocietyShow more - ItemMagnetic state selected by magnetic dipole interaction in the kagome antiferromagnet NaBa2Mn3F11(American Physical Society, 2018-02-12) Hayashida, S; Ishikawa, H; Okamoto, Y; Okubo, T; Hiroi, Z; Avdeev, M; Manuel, P; Hagihala, M; Soda, M; Masuda, T
Show more We haved studied the ground state of the classical kagome antiferromagnet NaBa2Mn3F11. Strong magnetic Bragg peaks observed for d spacings shorter than 6.0 Å were indexed by the propagation vector of k0=(0,0,0). Additional peaks with weak intensities in the d-spacing range above 8.0 Å were indexed by the incommensurate vector of k1=[0.3209(2),0.3209(2),0] and k2=[0.3338(4),0.3338(4),0]. Magnetic structure analysis unveils a 120∘ structure with the tail-chase geometry having k0 modulated by the incommensurate vector. A classical calculation of the Heisenberg kagome antiferromagnet with antiferromagnetic second-neighbor interaction, for which the ground state a k0120∘ degenerated structure, reveals that the magnetic dipole-dipole (MDD) interaction including up to the fourth neighbor terms selects the tail-chase structure. The observed modulation of the tail-chase structure is attributed to a small perturbation such as the long-range MDD interaction or the interlayer interaction. ©2018 American Physical SocietyShow more - ItemMagnetic structure and dielectric state in the multiferroic Ca2CoSi2O7(The Physical Society of Japan, 2017-05-10) Soda, M; Hayashida, S; Yoshida, T; Akaki, M.; Hagiwara, M; Avdeev, M; Zaharko, O; Masuda, T
Show more The magnetic structure of the multiferroic Ca2CoSi2O7 was determined by neutron diffraction techniques. A combination of experiments on polycrystalline and single-crystal samples revealed a collinear antiferromagnetic structure with the easy axis along the 〈100〉 directions. The dielectric state is discussed in the framework of the spin-dependent d–p hybridization mechanism, leading to the realization of the antiferroelectric structure. The origin of the magnetic anisotropy is discussed in comparison with that of the isostructural Ba2CoGe2O7. ©2017 The Physical Society of JapanShow more - ItemNeutron scattering study in breathing pyrochlore antiferromagnet Ba3Yb2Zn5O11(International Conference on Neutron Scattering, 2017-07-12) Masuda, T; Haku, T; Soda, M; Sera, M; Kimura, K; Taylor, J; Itoh, S; Yokoo, T; Matsumoto, Y; Yu, DH; Mole, RA; Takeuchi, T; Nakatsuji, S; Kohno, Y; Sakakibara, T; Chang, LJ
Show more Comprehensive study on breathing pyrochlore antiferromagnet Ba3Yb2Zn5O11 [1] is presented. To identify the energy scheme of crystalline electric field (CEF), we performed inelastic neutron scattering (INS) measurement in high energy range. The observed dispersionless excitations are explained by a CEF Hamiltonian of Kramers ion Yb3+ of which the local symmetry exhibits C3v point group symmetry. The magnetic susceptibility is consistently reproduced by the energy scheme of the CEF excitations. To identify the spin Hamiltonian we performed INS experiment in low energy range and thermodynamic property measurements at low temperatures. The INS spectra are quantitatively explained by spin-1/2 single-tetrahedron model having XXZ anisotropy and Dzyaloshinskii-Moriya interaction. This model has a two-fold degeneracy of the lowest-energy state per tetrahedron and well reproduces the magnetization curveat 0.5 K and heat capacity above 1.5 K. At lower temperatures, however, we observe a broad maximum in the heat capacity around 63 mK, demonstrating that a unique quantum ground state is selected due to extra perturbations with energy scale smaller than the instrumental resolution of INS. Possible mechanisms for the ground state selection are discussed [2].Show more - ItemNeutron scattering study of the quasi-one-dimensional antiferromagnet Ba2CoSi2O7(American Physical Society, 2019-10-07) Soda, M; Hong, T; Avdeev, M; Yoshizawa, H; Masuda, T; Kawano-Furukawa, H
Show more Magnetization and neutron scattering measurements have been carried out on an antiferromagnet Ba2CoSi2O7. The observed magnetic excitation is almost dispersionless, and the neutron intensity is only modulated along the [101] direction. The dispersionless magnetic excitation suggest that the Ba2CoSi2O7 system is a quasi-one-dimensional antiferromagnet. Classical spin-wave theory for a one-dimensional antiferromagnet can explain the dispersionless spin excitation. The magnetic structure determined by the measurement of the neutron powder diffraction is consistent with no observation of the multiferroic property in this system. ©2019 American Physical SocietyShow more - ItemStripy 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
Show more 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.Show more