INTERPRETATION OF CRYSTAL-FIELD PARAMETERS IN RARE-EARTH-SUBSTITUTED GARNETS

Crystal-field parameters of Vb3+, Eu3+, Tm 3+, Sm3+, Dy3+, and Er3+ ions in various garnet lattices have been analyzed using a development of the superposition model proposed by Bradbury and Newman. This effects, in principle, the separation of the crystal-field contributions of the different coordinated O2- ions and determines power laws and the angular distortion near substituted ions. A realistic separation of the contributions to the w = 4 parameters is obtained even when no allowance is made for local distortion. However, owing to their greater angular sensitivity, the contributions to the n = 6 parameters can only be separated if local angular distortions of up to 9° are allowed for. Results derived for single-ligand parameters and power laws are in good accord with theoretical results obtained for other rare-earth systems.