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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.

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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