Fine-Tuning the Cr³⁺ R₁-Line by Controlling Pauli Antisymmetry Strength

Fine-tuning of the Cr³⁺ zero-phonon R₁-line fluorescence (²E-⁴A₂) has recently been achieved by varying the composition of Cr-doped solid solution garnets. Chemical substitutions of Y³⁺ with Lu³⁺ and Tb³⁺ produce R₁-line shifts and multiplets that cannot be associated with direct or indirect changes in the Cr-O covalency alone and raise important questions on the nature of the interactions between the CrO₆ active center and its environment, hence on the impact of local disorder. In this Letter we show that Pauli antisymmetry interactions with next-nearest neighbor ions, which are commonly omitted from theoretical analyses, induce a nephelauxetic effect on the CrO₆ active center that shifts the R₁-line. The strength of these interactions increases with the ionic radius and number of codopant ions, all of it resulting in controlled shifts and multiplets of R₁-lines. The Pauli antisymmetry induced nephelauxetic effect, combined with the R₁-line shift with lattice constant, allows for a very fine-tuning of the Cr³⁺ R₁-line.