Superposition-model analysis of the spin-strain coupling tensor in ruby

Expressions for the elements G pq of the spin-strain coupling tensor have been derived for ruby (Al 2 O 3 :Cr 3+ ) in terms of the superposition-model parameters describing the axially symmetric field of each ligand. Four intrinsic parameters, A 2 , A 4 and their radial derivatives, provide a reasonable fit to the ten G pq but the zero-field splitting D cannot be fitted and must be largely due to other mechanisms. The parameters obtained are used to estimate the elements of the G tensor in MgO:Cr 3+ and these are compared with measured values.