Spin–Lattice Coupling Coefficients G_ij for Trigonal Al₂O₃:Fe³⁺ and ZnSiF₆ · 6H₂O:Ni²⁺ Crystals²⁾

By expressing the six spin–lattice coupling coefficients G in trigonal symmetry in terms of the coefficients G and G in cubic symmetry, the coefficients G for trigonal Al₂O₃ : Fe³⁺ and ZnSiF₆ · 6 H₂O : Ni²⁺ crystals are calculated from the values of G and G obtained from a simple and uniform method within the framework of cubic symmetry approximation. The results for the Al₂O₃ : Fe³⁺ crystal is in agreement with the experimental findings, whereas for ZnSiF₆ · 6 H₂O : Ni²⁺, the agreement for part of coefficients is poor. The reasons for the disparity are discussed.