Magnetism in a Disordered Co-honeycomb

The search for magnetic materials displaying physics associated with Kitaev’s exactly solvable S=1/2 honeycomb lattice model is a focal point of contemporary research due to the model’s unique quantum spin liquid ground state and application towards fault tolerant quantum computing. Initial candidate materials focused on 4d/5d Mott insulators, but a more recent extension to 3d materials has led to a large body of work focused mostly on high-spin Co²⁺ systems realizing a Kramer’s doublet j_eff = 1/2 ground state. One promising candidate material is Na₂Co₂TeO₆. While the nature of the magnetism in Na₂Co₂TeO₆ remains an open topic, the onset of zig-zag magnetic order below T_N = 27 K clearly indicates non-Kitaev terms present in the low-energy Hamiltonian. In the Kitaev candidate material α-RuCl₃, substituting nonmagnetic Ir³⁺ for Ru³⁺ suppressed conventional long-range magnetic order while keeping the signatures of fractionalized excitations, suggesting magnetic dilution as a promising route. Here we explore substitution of nonmagnetic ions for Co²⁺. We present magnetometry and specific heat measurements on synthesized powders of disordered Na₂Co_2-xR_xTeO₆ (R = Mg, Zn) and discuss the effect of magnetic dilution on the complex magnetism found in the parent compound.