Defect models of two tetragonal Ce3+ centers T1 and T2 in Ce3+-doped cubic fluorperovskites KMgF3 and BaLiF3

The EPR g factors g|| and g⊥ for two tetragonal Ce3+ centers T1 and T2 in Ce3+-doped cubic fluorperovskites KMgF3 and BaLiF3 are calculated from the complete diagonalization (of energy matrix) method (where all the Kramers doublets within the ground and excited multiplets 2F5/2 and 2F7/2 are contained). The calculations show that the simple method of calculating g factors (where only the doublets within the ground multiplet 2F5/2 are considered) used in the previous papers cannot give the correct signs of crystal-field parameter B20 and hence the reasonable defect models for these tetragonal Ce3+ centers (in fact, physically, these defect models are inconsistent). The new and consistent defect models for these Ce3+ centers are suggested as follows: in KMgF3:Ce3+, centers T1 and T2 are the substitution of Ce3+ for K+ with a nearest interstitial F− and, respectively, with and without a nearest K+ vacancy (VK) along C4 axis, and in BaLiF3:Ce3+, centers T1 and T2 are the substitution of Ce3+ for Ba2+ with, respectively, a nearest interstitial F− and a nearest Ba2+ vacancy along C4 axis because of charge compensation. Based on these defect models and by considering the orbit reduction effect due to the covalence of Ce3+–F− bonds, the g factors of these tetragonal centers are explained reasonably. The results (in particular, the approximations of the defect structural data for these tetragonal centers) are discussed.

► g Factors of two tetragonal Ce3+ centers T1, T2 in KMgF3 and BaLiF3 are calculated. ► The calculations are from the complete diagonalization (of energy matrix) method. ► The defect models of these Ce3+ centers are obtained from the calculations. ► These defect models and parameters B20 differ from those in the previous paper.