Modification of magnetic structure-property relationships in chemically substituted layered honeycomb oxide

In honeycomb layered transition metal oxides, competing exchange interactions between neighboring magnetic ions often give rise to complex magnetic ground states, which are highly sensitive to structural perturbations. The honeycomb compound Na_₃Ni_₂SbO_₆ crystallizes in a structure comprising magnetic layers of edge-sharing NiO_₆ and SbO_₆ octahedra arranged in a honeycomb lattice, interleaved with non-magnetic NaO_₆ layers. This compound undergoes long-range antiferromagnetic (AFM) ordering below the Néel temperature T_N ≈ 18 K, despite the coexistence of competing ferromagnetic (FM) correlations suggested by a small positive Weiss constant. To investigate the tunability of the magnetic properties, we introduce Sn^⁴⁺ into the honeycomb layer. This chemical substitution results in an expansion of the unit cell and systematically suppresses T_N. Beyond a critical concentration, we observe a pronounced drop in the transition temperature to ~6 K, signaling a transition to a new magnetic ground state. We perform a detailed structural and magnetic characterization of the resulting series of chemically substituted compounds, elucidating the interplay between lattice modifications and the dominant magnetic interactions across the series.