Site occupancy and spectroscopic properties of Mn4+ in double perovskites, La2MgGeO6

Abstract The spectroscopic properties of Mn4+ (3 d3) in the La2MgGeO6 double perovskite is the subject of this investigation. The optical data have been used to perform detailed crystal field calculation of the Mn4+ energy level scheme. In La2GeMgO6, the Mn4+ can occupy either the octahedral Mg2+ or the Ge4+ sites. To address the question of site occupation, the Mn4+ energy levels were calculated when the ion substitutes for the Mg2+ and Ge4+ sites of the double perovskite lattice. An unambiguous decision on the site occupation cannot be reached based on our calculations. A comparative study of the variations in the energy of the 2Eg→4A2g emission transition in a series of materials with the double perovskite structure is presented. The energy of the 2Eg→4A2g emission transition tends to increase with increasing distortion of the octahedral O–Mn–O bond angle from the ideal 90°.