Optical spectroscopy and crystal field studies of the Mn⁴⁺ ion (3d³) in the double perovskite NaLaMgTeO₆

The spectroscopic properties of the Mn⁴⁺ ion (3d³) in the double perovskite NaLaMgTeO₆ are reported in this work. Evidence is presented for the occupation by the Mn4+ ion of both the six coordinated Mg²⁺ and Te⁶⁺ sites in the host structure. The Mn ⁴⁺ energy levels are calculated using the exchange charge model of crystal field theory for both occupied sites. The results of our calculations yield the crystal field splitting and Racah parameters of D_q = 2008 cm^-1, B = 790 cm^-1, C =2881 cm^-1, with C/B=3:65 (Mg²⁺ site) and D_q=2008 cm^-1, B=790 cm ^-1, C =2949 cm^-1, with C=B = 3:73 (Te⁶⁺ site). A cross-cutting comparative study of the variations in the crystal field splitting and the Racah parameters of the six-coordinated Mn⁴⁺ ion in a series of materials with the perovskite structure are presented.