Suppression of the antiferromagnetic order by Zn doping in a possible Kitaev material Na\(_2\)Co\(_2\)TeO\(_6\)

Very recently, a 3\(d\) based honeycomb cobaltate Na\(_2\)Co\(_2\)TeO\(_6\) has garnered tremendous attention due to the proposed proximity to the Kitaev spin-liquid state as its 4\(d\)/5\(d\) counterparts. Here, we use Zn to substitute Co in a broad range and perform systematic studies on Na\(_2\)Co\(_{2-x}\)Zn\(_x\)TeO\(_6\) by structural, magnetic, and thermodynamic measurements, and track the doping evolution of its magnetic ground states. Due to the extremely close radii of Zn\(^{2+}\) and high-spin Co\(^{2+}\) ions, the substitution can be easily achieved. X-ray diffractions reveal no structural transition but only minor changes on the lattice parameter \(c\) over a wide substitution range \(0 \leq x \leq 1.5\). 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 \(\sim1.0\). Then it evolves into a spin-glass phase with short-range order that is rapidly supplanted by a magnetically disordered state when \(x \geq 1.3\). By summarizing all these data, we construct a magnetic phase diagram of Na\(_2\)Co\(_{2-x}\)Zn\(_x\)TeO\(_6\). Our results demonstrate that the Zn doping can effectively suppress the magnetic order and induce a possibe quantum paramagnetic state. These may serve as a platform to investigate the Kitaev physics in this system.