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  • Letter
  • Open Access

Bond-dependent interactions and ill-ordered state in the honeycomb cobaltate BaCo2(AsO4)2

A. Devillez1, J. Robert1, E. Lhotel1, R. Ballou1, C. Cavenel1, F. Denis Romero1, Q. Faure2, H. Jacobsen3,4, J. Lass3 et al.

D. G. Mazzone3, U. Bengaard Hansen5, M. Enderle5, S. Raymond6, S. De Brion1,*, V. Simonet1,†, and M. Songvilay1,‡

  • *Contact author: sophie.debrion@neel.cnrs.fr
  • †Contact author: virginie.simonet@neel.cnrs.fr
  • ‡Contact author: manila.songvilay@neel.cnrs.fr
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Phys. Rev. Research 7, L042040 – Published 21 November, 2025

DOI: https://doi.org/10.1103/f9sk-zfqc

Abstract

The ground state and Hamiltonian of the honeycomb lattice material BaCo2(AsO4)2 hosting magnetic Co2+ have been debated for decades. The recent proposal for anisotropic bond-dependent interactions in such honeycomb cobaltates has raised the prospect of revisiting its Hamiltonian in the context of Kitaev physics. To test this hypothesis, we have combined magnetization, ac susceptibility, and neutron scattering measurements on a BaCo2(AsO4)2 single crystal, together with advanced modeling. Our experimental results highlight a collinear magnetic ground state with intrinsic disorder associated with an average incommensurate propagation vector. Monte Carlo simulations and linear spin wave calculations were performed to obtain a spin model compatible with this unusual ground state, the dispersion of magnetic excitations, and a magnetization plateau under magnetic field. We thus show that bond-dependent anisotropic interactions, including Kitaev-like interactions, are necessary to account for the puzzling properties of this long-explored material, and are hence a general ingredient in the cobaltates.

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Phys. Rev. Research 7, L042040– Published 21 November, 2025
  • Received 10 April 2025
  • Accepted 10 October 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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