Suppression of the antiferromagnetic order by Zn doping in a possible Kitaev material Na2Co2TeO6

Very recently, a 3d based honeycomb cobaltate Na2Co2TeO6 has garnered tremendous attention due to the proposed proximity to the Kitaev spin-liquid state as its 4d/5d counterparts. Here, we use Zn to substitute Co in a broad range and perform systematic studies on Na2Co2-xZnxTeO6 by structural, magnetic, and thermodynamic measurements, and track the doping evolution of its magnetic ground states. Due to the extremely close radii of Zn2+ and high-spin Co2+ ions, the substitution can be easily achieved. X-ray diffractions reveal no structural transition but onlyminor changes on the lattice parameter c over a wide substitution range 0 <= x <= 1.5. Magnetic susceptibility and specific heat measurements both suggest an antiferromagnetic ground state which is gradually suppressed with doping. It can survive with x up to similar to 1.0. Then it evolves into a spin-glass phase with short-range order that is rapidly supplanted by a magnetically disordered state when x >= 1.3. By summarizing all these data, we construct a magnetic phase diagram of Na2Co2-xZnxTeO6. Our results demonstrate that the Zn doping can effectively suppress the magnetic order and induce a possible quantum paramagnetic state. These may serve as a platform to investigate the Kitaev physics in this system.