(Z=Cu, Co, Ni, Zn, Fe) Compositionally Complex Oxides

High-entropy oxides (HEOs) have recently emerged as promising candidates for designing novel functional materials by combining multiple transition-metal ions into a single crystallographic site. In this study, we investigate the structural and magnetic properties of compositionally complex layered honeycomb oxides Na₂Z₂TeO₆ (Z = Cu, Co, Ni, Zn, Fe), where chemical substitution at the Ni site enables both structural stabilization and magnetic tuning. CCO-I Na₂(Ni₀.₅₀Cu₀.₂₀Zn₀.₁₀Fe₀.₁₀Co₀.₁₀)₂TeO₆, CCO-II Na₂(Ni₀.₅₀Fe₀.₁₀Co₀.₄₀)₂TeO₆, CCO-III Na₂(Ni₀.₅₀Zn₀.₁₀Fe₀.₁₀Co₀.₃₀)₂TeO₆, and CCO-IV Na₂(Ni₀.₅₀Cu₀.₁₀Zn₀.₁₀Fe₀.₁₀Co₀.₂₀)₂TeO₆ were synthesized via solid-state reaction. Powder X-ray diffraction combined with Rietveld refinement confirms that all compounds crystallize in the P6₃/mcm space group, preserving the layered honeycomb structure. Magnetic susceptibility measurements reveal suppressed antiferromagnetic transitions with Néel temperatures ranging from ~14 K to ~25 K, depending on composition, consistent with dilution effects and competing exchange interactions. These results demonstrate that cationic disorder and competing magnetic sublattices can destabilize long-range antiferromagnetism, potentially favoring spin-glass-like states.