Synthesis, Structure and Magnetic Properties of a New Spin-1 Honeycomb Lattice KNiAsO₄ with a Zig-Zag Magnetic Structure

Identifying and characterizing new honeycomb magnetic systems are the key ingredients to explore new candidate materials for the Kitaev model as the model realizes the exact quantum spin liquids ground state. Recently the Kitaev model with higher spins ( <i>S</i> = 1) systems have been proposed as candidate materials to host the quantum spin liquid state. Honeycomb compound, KNiAsO4, is one such magnetic system and here, we present a comprehensive series of magnetic and neutron scattering measurements and evaluate the potential for Kitaev physics via the experimental determination of the spin-Hamiltonian. Bulk magnetic measurements of KNiAsO4 reveal an antiferromagnetic transition at ∼ 19 K which is generally robust to applied magnetic fields. Neutron diffraction measurements show magnetic order with a k = ( 3/2 , 0, 0) ordering vector which results in the well-known “zigzag” magnetic structure thought to be adjacent to the spin-liquid ground state. Inelastic neutron scattering experiments show a well defined gapped spin-wave spectrum with no evidence of the continuum expected for fractionalized excitations. Modeling of the spin waves shows that the extended Kitaev spin-Hamiltonians is generally necessary to model the spectra and reproduce the observed magnetic order. Overall, our results demonstrate that the KNiAsO4 is a promising candidate to study Kitaev physics associate with spin-1 honeycomb system.