Enhancement of A′-site Mn~(3+) spin ordering by B-site Mn~(4+) substitution in quadruple perovskite PbMn_3Cr_3MnO_(12)

摘要

An A-site ordered but B-site disordered quadruple perovskite oxide PbMn_3Cr_3MnO_(12) was synthesized by high-pressure and high-temperature methods. The compound crystallizes in space group Im-3 with the charge distribution of Pb~(2+)Mn~(3+)_3Cr~(3+)_3Mn~(4+)O_(12). Three antiferromagnetic phase transitions are found to occur at T_(N1)≈ 155, T_(N2)≈ 81, and T_(N3)≈ 74 K, respectively, due to the complex B-site and A'-B intersite spin interactions. Compared with the isostructural LaMn_3Cr_4O_(12) with negligible A'-B intersite spin coupling, the substitution of Mn~(4+), which has identical electronic configuration to that of Cr~(3+) (t_(2g)~3), 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 PbMn_3Cr_3MnO_(12). This work opens up a way to enhance the A'-site spin ordering temperature in quadruple perovskite oxides.