Synthesis and Characterization of Metastable Cobalt Honeycomb KCoAsO₄

The Kitaev model has served as a long-sought-after target in the realization of a quantum spin liquid that could host Majorana Fermions. Such non-Abelian anyons could revolutionize quantum computing if properly implemented to overcome decoherence. A 3d⁷ electronic configuration, like Co²⁺, has been explored by theory and experimental work to design Kitaev materials. Here, we report the synthesis of a new cobaltate honeycomb material KCoAsO₄. The compound is synthesized through a low-temperature solution route and crystallized in space group R¯3 with lattice parameters a = 5.0394(1) and c = 28.6790(1) as determined by neutron powder diffraction. The crystal structure follows motifs similar to those of the honeycomb compound BaCo₂(AsO₄)₂ but presents differing magnetic behavior. Magnetization/heat capacity measurements on the powder show antiferromagnetic transition T_N = 14 K. Two lower-temperature transitions are present in susceptibility at low field that resemble spin reorientations. Magnetization data as a function of field have curvature indicative of metamagnetic behavior below the magnetic ordering temperature, with the magnetic ordering suppressed upon application of a higher magnetic field. Computational studies suggest the presence of a weak nearest-neighbor Kitaev term, K₁, consistent with related honeycomb cobaltates. Together, the data suggest that this material should present a new platform for developing Kitaev quantum spin liquids.