Refining interaction parameters in Honeycomb-Lattice Antiferromagnets Na₃Co₂SbO₆ and Na₃Ni₂BiO₆

Since the discovery of the exactly solvable Kitaev model, Kitaev honeycomb lattices have emerged as a promising platform to realize a quantum spin liquid (QSL) state in frustrated magnetic systems. Over the years, candidate materials for studies into Kitaev systems have utilized magnetic atoms with progressively smaller valence orbitals, from 5d iridium, to later 4d ruthenium and 3d cobalt- and nickel-based systems, as the weaker spin-orbit coupling is believed to be outweighed by the relative weakness of non-Kitaev and further-neighbor interactions. Using the monoclinic honeycomb antiferromagnetic materials Na₃Co₂SbO₆ (NCSO) and Na₃Ni₂BiO₆ (NNBO) as examples, we will showcase the sensitivity of modeled infrared absorption to Kitaev model parameters as a utility to refine the parameters for candidate QSL materials. Our results exhibit improved agreement between calculated linear spin wave features and magneto-infrared spectroscopy measurements.