Theoretical investigation of the EPR parameters and local structure for trigonal Yb3+ ion in Bi4Ge3O12 crystal

Bi4Ge3O12 single crystals are ofgreat interest for science research and engineering applications. In this paper, the electron paramagnetic resonance (EPR) g factors g(parallel to), g(perpendicular to) of Yb3+ and hyperfine structure constants A(parallel to), A(perpendicular to) of Yb-171(3+) and Yb-173(3+) isotopes in Bi4Ge3O12 crystal are calculated from the perturbation formulas of these parameters. The crystal-field parameters are obtained from the superposition model and the crystal structure data. The EPR parameters for trigonal Yb3+ centers in Bi4Ge3O12 are reasonably explained by involving the defect structures of impurity Yb3+ centers. Based on the calculations, Yb3+ ion is found not to occupy exactly the host Bi3+ site, but to shift away from the center of oxygen octahedron by a distance Delta Z approximate to 0.317 angstrom along C-3 axis. The results are discussed. (C) 2007 Elsevier B.V. All rights reserved.