Theoretical investigation of EPR parameters for two trigonal Yb 3+ centers in LiNbO 3 and LiNbO 3:MgO crystals

Abstract

The perturbation formulas of EPR parameters ( g factors g ∥, g ⊥ and hyperfine structure constants A ∥, A ⊥) for the lowest Kramers doublet Γ 6 or Γ 7 of 2F 7/2 of 4f 13 ion in trigonal symmetry are established. In these formulae, the contributions of the covalency effects, the admixture between J=7/2 and 5/2 states as well as the second-order perturbation (which is not considered in the previous works) are all included. From these formulae, the EPR parameters for two trigonal Yb 3+ centers in LiNbO 3 and MgO codoping LiNbO 3 crystals are reasonably explained by considering suitable defect structures of these centers. The results (including the relative importance of second-order perturbation contribution) are discussed.