Large splittings of the 4f shell of Ce3+ in garnets
Ab initio embedded cluster calculations on Ce3+-doped Y3Al5O12, Lu3Al5O12, Gd3Al5O12, Y3Ga5O12, Lu3Ga5O12, and Gd3Ga5O12, which do not make use of any adjustable parameter, support recent assignments of the seventh 4f level of Ce3+ in garnets [Przybylińska et al., Appl. Phys. Lett., 2013, 102, 241112] and that the splitting of the 4f shell of Ce3+ in these materials is slightly smaller than 4000 cm−1 and much larger than the 2000–2500 cm−1 commonly assumed in analyses of 5d → 4f emission bands. Why this wrong assumption has been working well so far is explained by the fact that the intensity of the emission to the seventh level of the 4f1 configuration is found to be only one hundredth of the integrated intensity of the emissions to the other six levels, which group themselves into two sets of three individual levels separated by 2000–2500 cm−1. The effective field splitting and the spin–orbit coupling splitting are found to be of the same size. From a strong field coupling point of view, the first six levels result from the interactions between 2T2u and 2T1u cubic levels and the higher, isolated seventh level comes directly from the cubic 2A2u. From a weak field coupling point of view, the first three levels result from the splitting of 2F5/2, the second three levels from the splitting of 2F7/2 and the seventh level from a strong, cubic field driven interaction between 2F7/2 and 2F5/2 components [Herrmann et al., J. Appl. Phys., 1966, 37, 1312].