Investigation of the local structure and EPR spectra for Nd3+ in Bi4Ge3O12

On the basis of complete energy matrices for a 4f3 configuration ion in trigonal symmetry ligand-field, the optical and EPR spectra of Nd3+ center in Bi4Ge3O12 have been reasonably explained. The results indicate that the Nd3+ ion do not occupy the actual Bi3+ site, but departure from the ideal host position along the C3 axis by about 0.07 Å. The new set of crystal-field parameters that can well account for the Stark levels and EPR parameters have been obtained from the superposition model. Moreover, the influence of orbital reduction factor k and local distortion parameter ΔZ on EPR parameters is analyzed.