ANi ₂ TeO ₆ (A = Sr, Ca, and Cd): Canted Antiferromagnets Featuring a CaFe ₂ O ₄ -Type Superstructure with Double 2:1 Cationic Ordering

The intriguing magnetism of CaFe₂O₄-type oxides arises from the coexistence of a honeycomb-like network and one-dimensional zigzag ladders, providing a platform for unconventional magnetic states. In this work, we strategically introduced long-range cationic ordering into this framework to tune competing magnetic interactions. Here, a series of ordered CaFe₂O₄-type oxides A□_1/2Ni₂TeO₆ (ANi₂TeO₆, A = Sr, Ca, or Cd; □ = A-site vacancy) were rationally designed, synthesized, and structurally characterized. ANi₂TeO₆ crystallizes in <i>Pnma</i> with a 3-fold superstructure originating from the 2:1 ordering of Ni²⁺ and Te⁶⁺ cations along two symmetry-independent zigzag ladders. This ordering further triggers a 2:1 periodic arrangement of A²⁺ cations and vacancies along the hexagonal tunnel, minimizing the cation-cation electrostatic repulsion. Low-temperature NPD analysis reveals alternating ferromagnetic and antiferromagnetic coupling within each ladder, with Ni2²⁺ spin moments adopting an up-up-down-down configuration along the <i>b</i>-axis, whereas Ni1²⁺ spins are canted within the <i>ab</i>-plane, producing a net magnetic moment along the <i>a</i>-axis and thus a ferromagnetic-like magnetic transition. Adjacent ladders couple antiferromagnetically, yielding a magnetic structure consistent with <i>Pnm</i>'<i>a</i>'. This work establishes a strategy of cationic ordering to expand the structural chemistry of CaFe₂O₄-type oxides, thereby offering new opportunities for the study of competing magnetic interactions and the development of novel magnetic materials.