Crystal field studies of the Mn⁴⁺ energy levels in the perovskite, LaAlO₃

The electronic energy levels of the Mn⁴⁺ (3d³) ion in the rhombohedral perovskite, LaAlO₃, have been calculated using the exchange charge model of crystal field theory. The calculated Mn⁴⁺ energy levels are in good agreement with the experimental spectra that have been presented in the literature. The results of our calculations yield the crystal field splitting and Racah parameters of Dq = 2123 cm^-1, B = 695 cm^-1 and C = 2941 cm^-1, with C/B = 4.2. A cross-cutting comparative study of the variation in the crystal field splitting and the Racah parameters of the octahedrally coordinated Mn⁴⁺ ion in a series of materials with the perovskite structure is also presented. We have also introduced a dimensionless parameter (β₁) which quantifies the nephelauxetic effect and predicts the energy of the ²E_g → ⁴A_2g emission transition in the perovskites.