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

Abstract The spectroscopic properties of Mn 4+ (3 d 3 ) in the La 2 MgGeO 6 double perovskite is the subject of this investigation. The optical data have been used to perform detailed crystal field calculation of the Mn 4+ energy level scheme. In La 2 GeMgO 6 , the Mn 4+ can occupy either the octahedral Mg 2+ or the Ge 4+ sites. To address the question of site occupation, the Mn 4+ energy levels were calculated when the ion substitutes for the Mg 2+ and Ge 4+ 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 2 E g → 4 A 2g emission transition in a series of materials with the double perovskite structure is presented. The energy of the 2 E g → 4 A 2g emission transition tends to increase with increasing distortion of the octahedral O–Mn–O bond angle from the ideal 90°.