Theoretical investigation of EPR parameters for two trigonal Yb3+ centers in LiNbO3 and LiNbO3:MgO crystals Original Research Article

The perturbation formulas of EPR parameters (g factors g∥, g⊥ and hyperfine structure constants A∥, A⊥) for the lowest Kramers doublet Γ6 or Γ7 of 2F7/2 of 4f13 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 Yb3+ centers in LiNbO3 and MgO codoping LiNbO3 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.