Ca₂MnO₃X (X = Cl, Br) Oxyhalides with 1-Dimensional Ferromagnetic Chains of Square-Planar S=2 Mn³⁺

Mixed anion oxyhalides with the formula Ca2MnO3X (X = Cl, Br) are synthesized using solid-state reaction methods. These two materials crystallize in a novel structure type due to the small ionic radius of Ca and the strong Jahn-Teller effect of Mn3+. The resulting structure (space group Cmcm) contains one-dimensional chains of MnO4 square planes, with an angle of similar to 120 degrees between neighboring planes. At low temperatures, the two materials adopt magnetic arrangements, with ferromagnetic chains coupled antiferromagnetically. On applying a magnetic field, both materials experience spin-flop transitions.