Enhancement of A′-site Mn3+ spin ordering by B-site Mn4+ substitution in quadruple perovskite PbMn3Cr3MnO12

An A-site ordered but B-site disordered quadruple perovskite oxide PbMn3Cr3MnO12 was synthesized by high-pressure and high-temperature methods. The compound crystallizes in space group Im-3 with the charge distribution of Pb2+Mn3+3Cr3+3Mn4+O12. Three antiferromagnetic phase transitions are found to occur at TN1 ≈ 155, TN2 ≈ 81, and TN3 ≈ 74 K, respectively, due to the complex B-site and A′-B intersite spin interactions. Compared with the isostructural LaMn3Cr4O12 with negligible A′-B intersite spin coupling, the substitution of Mn4+, which has identical electronic configuration to that of Cr3+ (t2g3), into the B site can introduce A′-B intersite spin interactions. As a result, the A′-site spin-related ordering temperature increases significantly, while the B-site one remains little changed in the current PbMn3Cr3MnO12. This work opens up a way to enhance the A′-site spin ordering temperature in quadruple perovskite oxides.