Chemical ordering and magnetic phase transitions in multiferroic BiFeO3-AFe(1/2)Sb(1/2)O(3) (A-Pb, Sr) solid solutions fabricated by a high-pressure synthesis

Ceramic samples of BiFeO3-based perovskite solid solutions with the highly ordered complex perovskites PbFe1/2Sb1/2O3 (PFS) and SrFe1/2Sb1/2O3 (SFS) were obtained using high-pressure synthesis at 4-6 GPa. Mossbauer studies revealed that BiFeO3-SFS compositions are characterized by a larger compositional inhomogeneity as compared to BiFeO3-PFS ones. In line with this result, concentration dependence of the magnetic phase transition temperature T-N for BiFeO3-SFS compositions is close to the T-N(x) dependence for BiFeO3 solid solution with disordered perovskite PbFe1/2Nb1/2O3 (PFN). In contrast to this T-N(x) dependence for BiFeO3-PFS compositions nicely follows the theoretical T-N(x) dependence calculated for the case of the ordered distribution of Fe3+ and non-magnetic Sb5+ ions in the lattice (chemical ordering).