An investigation of the EPR zero-field splitting of Cr3+ ions at the tetragonal site and the Cd2+ vacancy in RbCdF3:Cr3+ crystals

The quantificational relationship between the EPR zero-field splitting parameter D and the structure parameters of the tetragonal Cr3+ centre in RbCdF3:Cr3+ crystals has been established according to the superposition model and third-order perturbation theory. The existence of the Cd2+ vacancy and the lattice distortion have been verified. Meanwhile, we obtain that the F- ion moves toward the central Cr3+ ion by X1 = 0.0031 nm, X2 = 0.001 01 nm, X3 = 0.002 81 nm. Good agreement between the theoretical results and the experimental values shows that the assumption of the Cd2+ vacancy and the lattice distortion is reasonable. Although the main source of the tetragonal crystal field comes from the Cd2+ vacancy caused by the charge compensation, the contribution of the lattice distortion cannot be neglected. (author)