Browsing by Author "Ueta, D"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Crystal structure and magnetic properties of the breathing kagome ising antiferromagnet Yb3Ni11Ge4.63
    (The Physical Society of Japan, 2020-07-31) Takahashi, M; Nawa, K; Okuyama, D; Nojiri, H; Frontzek, MD; Avdeev, M; Yoshida, M; Ueta, D; Yoshizawa, H; Sato, TJ
    We have investigated magnetic properties of the rare-earth based intermetallic compound Yb3Ni11Ge4.63 (YNG), where Yb3+ ions form a breathing-kagome lattice. Single-site 4f electron wavefunctions of the ground-state doublet are deduced from magnetization and heat capacity measurements. The Weiss temperatures are quite anisotropic as Θa = −0.01(2) K (H ∥ a) and Θc = −0.67(2) K (H ∥ c), indicating Ising-like spin–spin interactions dominating in this compound. Low-temperature neutron diffraction confirms absence of magnetic Bragg peaks down to 0.05 K, whereas enhancement of broad peaks below 0.8 K was observed, a signature of short-range spin correlations. Competing interactions on the breathing-kagome lattice would suppress a magnetic long-range order in YNG. ©2020 The Physical Society of Japan
  • No Thumbnail Available
    Item
    Degenerate ground state in the classical pyrochlore antiferromagnet Na3Mn(CO3)2Cl
    (American Physical Society, 2018-10-18) Nawa, K; Okuyama, D; Avdeev, M; Nojiri, H; Yoshida, M; Ueta, D; Yoshizawa, H; Sato, TJ
    In an ideal classical pyrochlore antiferromagnet without perturbations, an infinite degeneracy in a ground state leads to the absence of magnetic order and a spin-glass transition. Here we present Na3Mn(CO3)2Cl as a new candidate compound where classical spins are coupled antiferromagnetically on the pyrochlore lattice and report its structural and magnetic properties. The temperature dependences of the magnetic susceptibility and heat capacity and the magnetization curve are consistent with those of an S=5/2 pyrochlore lattice antiferromagnet with nearest-neighbor interactions of 2 K. Neither an apparent signature of a spin-glass transition nor magnetic order is detected in magnetization and heat capacity measurements or powder neutron diffraction experiments. On the other hand, antiferromagnetic short-range order of the nearest neighbors is evidenced by the Q dependence of the diffuse scattering which develops around 0.85Å−1. A high degeneracy near the ground state in Na3Mn(CO3)2Cl is supported by the magnetic entropy, estimated as almost 4JK−2mol−1 at 0.5 K. ©2018 American Physical Society
  • Thumbnail Image
    Item
    Magnetism of classical pyrochlore antiferromagnet Na3Mn(CO3)2Cl
    (American Physical Society, 2020-03-03) Nawa, K; Okuyama, D; Avdeev, M; Nojiri, H; Yoshida, M; Ueta, D; Yoshizawa, H; Sato, TJ
    Pyrochlore antiferromagnets have attracted interests in terms of unconventional ground states and spin excitations owing to competing interactions. When its magnetism is dominated by classical spins coupled by Heisenberg interactions, a spin liquid state is expected as its ground state because of infinite degeneracy in the ground state (R. Moessner and J. T. Chalker, Phys. Rev. Lett. 80, 2929 (1998); Phys. Rev. B 58, 12049 (1998).). In this research, we report structural and magnetic properties together with low-temperature neutron diffraction patterns on a new pyrochlore antiferromagnet Na3Mn(CO3)2Cl. The structure of Na3Mn(CO3)2Cl is isotypic with that of the Co-analogue Na3Co(CO3)2Cl, which exhibits all-in-all-out magnetic order below 1.5 K (Z. Fu et al., Phys. Rev. B 87, 214406 (2013)). On the other hand, no magnetic Bragg peak indicating a magnetic order was detected down to 0.05 K in Na3Mn(CO3)2Cl. A high degeneracy near the ground state is suggested by a magnetic entropy estimated from heat capacity experiments and enhancement of diffuse scattering from neutron diffraction experiments. © 2021 American Physical Society