Theoretical investigation of the EPR parameters and local structure for trigonal Yb 3+ ion in Bi 4Ge 3O 12 crystal

Abstract

Bi 4Ge 3O 12 single crystals are of great interest for science research and engineering applications. In this paper, the electron paramagnetic resonance (EPR) g factors g ||, g ⊥ of Yb 3+ and hyperfine structure constants A ||, A ⊥ of 171Yb 3+ and 173Yb 3+ isotopes in Bi 4Ge 3O 12 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 Yb 3+ centers in Bi 4Ge 3O 12 are reasonably explained by involving the defect structures of impurity Yb 3+ centers. Based on the calculations, Yb 3+ ion is found not to occupy exactly the host Bi 3+ site, but to shift away from the center of oxygen octahedron by a distance Δ Z ≈ 0.317 Å along C 3 axis. The results are discussed.