Comparison of 4f2energy parameters for Pr3+in cubic elpasolite crystals

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Abstract
Energy level data recently reported for the Cs2NaPrCl6, Cs2NaYCl6:Pr3+, and Cs2NaYBr6:Pr3+ systems are analysed in terms of a model hamiltonian that includes 14 ‘free-ion’ energy parameters and either two or four crystal-field energy parameters. Only one-electron crystal-field interactions are represented in the two-parameter crystal-field model, whereas the four-parameter model includes some (partial) consideration of two-electron crystal-field effects. Both crystal-field models assume octahedral (Oh ) site symmetry for the Pr3+ ions. The empirical energy level data for the respective systems are reasonably well fitted by calculations in which either nine or eleven of the parameters in the model hamiltonian are allowed to freely vary. Comparisons of the parameter values obtained from these data fits reveal significant differences in the crystal-field perturbations experienced by the 4f electrons of Pr3+ in Cs2NaPrCl6, Cs2NaYCl6:Pr3+, and Cs2NaYBr6:Pr3+. These perturbations are strongest in Cs2NaYCl6:Pr3+ and weakest in Cs2NaYBr6:Pr3+. ‘Intrinsic’ crystal-field parameters are derived for each system, and the values of these parameters are compared to those reported previously for LaCl3:Pr3+. Spin-correlated crystal-field (SCCF) parameters are reported for the Cs2NaPrCl6 and Cs2NaYCl6:Pr3+ systems.