High-Pressure Synthesized Perovskite CdMnO₃ with C-Type Antiferromagnetic Spin Configuration

CdMnO₃ had not been previously reported and was a missing piece in the A²⁺Mn⁴⁺O₃ series. We succeeded in synthesizing this compound by a high-pressure method and confirmed that it is crystallized in a distorted perovskite structure with a Cd²⁺Mn⁴⁺O₃ charge configuration. The obtained insulating CdMnO₃ exhibits an antiferromagnetic transition at about 86 K. First-principles calculations revealed that the Mn⁴⁺ (t_2g³) spins form a C-type antiferromagnetic structure, which is in sharp contrast to the G-type antiferromagnetism in the isostructural and isoelectronic CaMnO₃. Significant overlap of the Mn-3d and O(2)-2p orbitals produces distorted octahedra with a large Mn-O(1)-Mn tilt and induces antiferromagnetic couplings in the ac plane and the ferromagnetic couplings along the b axis.