Fe3+ defect dipole centers in ferroelectric PbTiO3 studied using electron paramagnetic resonance

Three Fe3+ centers with tetragonal symmetry and with the defect axis parallel to the polarization direction were detected in ferroelectric PbTiO3 crystals using electron paramagnetic resonance. All exhibit large zero-field splittings (ZFS). Two are assigned to Fe3+-oxygen vacancy dipole defect complexes, and the third to the isolated Fe3+ with distant charge compensation. The Fe3+-V-O defect with the largest ZFS converts to the second stable center on annealing; comparison of the cubic ZFS terms show the in-plane oxygen ligands relax outwards in stable center.