ANi₂TeO₆(A = Sr, Ca, and Cd): Canted Antiferromagnets Featuring a CaFe₂O₄-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 Pnma 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 b-axis, whereas Ni1²⁺ spins are canted within the ab-plane, producing a net magnetic moment along the a-axis and thus a ferromagnetic-like magnetic transition. Adjacent ladders couple antiferromagnetically, yielding a magnetic structure consistent with Pnm′a′. 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.