Synthesis and properties of a new quadruple perovskite: A-site ordered PbMn3Mn4O12

PbMn3Mn4O12 a quadruple perovskite was prepared by high pressure and high temperature synthesis. Powder X-ray diffraction (PXD) and differential scanning calorimetry reveal a structural phase transition at ∼380 K. Rietveld refinement of the synchrotron room temperature data indicate rhombohedral symmetry (R-3) with a=6.43675(4) Å and α=109.556(2)°. Similar 423 K PXD data refined in a body centered cubic cell (Im-3) with a=7.4283(9) Å. The temperature variation of magnetization, shows a magnetic field dependent antiferromagnetic-like transition at 68 K, and dynamic fluctuations indicative of magnetic frustration. The semiconducting electrical behavior indicates a large decrease in the conductivity near 68 K. The temperature dependence of the real part of the dielectric constant, εreal increases dramatically at ∼68 K, and shows relaxor-type ferroelectric behavior as a function of frequency. The intimate coupling of magnetic, electrical and dielectric properties at 68 K in PbMn3Mn4O12 suggests possible multiferroic behavior.