Kitaev-Γ-Heisenberg exchange in Ni<sup>3+</sup> honeycomb magnet NaNi<sub>2</sub>BiO<sub>6-δ</sub>

ORAL

Abstract

We present experimental and theoretical evidence for bond-dependent Kitaev-Γ-Heisenberg exchange in honeycomb Ni3+ magnet NaNi2BiO6-δ. Heat capacity and neutron diffraction reveal a low-temperature ordered magnetic state for T < 4.8 K with (1/3, 1/3, 0.15(1)) order. In-plane magnetic correlations match the 120° ordered state of the Kitaev-Γ-Heisenberg exchange. Electron spin resonance and density functional theory reveal a uniform 3+ valence in Ni intermediate between a S=3/2 and J=1/2 state. DFT shows that covalent bonding between oxygen and Bi produces an enhanced spin orbit coupling in Ni3+, which allows for strong bond-dependent exchange. The ordering wave vector, in-plane magnetic correlations, missing entropy, spin state, and superexchange pathways are all consistent with bond-dependent Kitaev-Γ-Heisenberg exchange interactions in NaNi2BiO6-δ.

*This work was supported by the Institute for Quantum Matter under DOE EFRC grant DE-SC0019331, and Gordon and Betty Moore foundation under the EPIQS program GBMF4532.

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Presenters

  • Allen Scheie

    • Oak Ridge National Lab
    • Johns Hopkins University
    • Oak Ridge National Laboratory
    • Institute for Quantum Matter, Johns Hopkins University

Authors

  • Allen Scheie

    • Oak Ridge National Lab
    • Johns Hopkins University
    • Oak Ridge National Laboratory
    • Institute for Quantum Matter, Johns Hopkins University

  • Collin Leslie Broholm

    • The Johns Hopkins University
    • Johns Hopkins University
    • Physics and Astronomy, Johns Hopkins University
    • Physics, The Johns Hopkins University
    • Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University

  • Kate Ross

    • Colorado State University
    • Physics, Colorado State University
    • Colorado State Univ
    • Department of Physics, Colorado State University

  • Panagiotis Peter Stavropoulos

    • University of Toronto
    • Physics, University of Toronto
    • Univ of Toronto

  • Elizabeth Seibel

    • Chemistry, Princeton University

  • Jose Rodriguez-Rivera

    • Center for Neutron Research, National Institute of Standards and Technology
    • National Institute of Standards and Technology
    • NIST Center for Neutron Research
    • NIST Center for Neutron Scattering

  • Joel Tang

    • Chemistry, Johns Hopkins University

  • Yi Li

    • Johns Hopkins University
    • Physics and Astronomy, Johns Hopkins University

  • Hae-Young Kee

    • University of Toronto
    • Physics, University of Toronto
    • Univ of Toronto

  • Robert J. Cava

    • Princeton University
    • Chemistry, Princeton University
    • Department of Chemistry, Princeton University
    • Chemistry, Pinceton University
    • Princeton Univ