Theoretical investigations of the EPR parameters for PbTiO3:Cr3+ bulks and nanopowders

The EPR parameters zero-field splitting D, g factors g// and g⊥ for the four centers (C1–C4) in PbTiO3:Cr3+ bulks and nanopowders are theoretically investigated from the perturbation formulas of the EPR parameters for a 3d3 ion in tetragonally distorted octahedra. Based on the studies, the impurity displacements ΔZ′ away from the center of the octahedron are obtained by analyzing the experimental EPR data. The results of the calculated D values in this work are compared with those based on the superposition model analyses in the previous works. The sign and magnitude of D and the impurity displacements in these centers are discussed.