Description:
Abstract The paper refers to the second-order spin-hamiltonian formalism, recently proposed by the author, describing the EPR properties of an exchange-coupled pair of orbitally not degenerate ions in the limit of strong isotropic exchange (higher-order effects such as biquadratic exchange or exchange striction are considered neglectable). Tables of numerical values for the relevant coefficients involved are given. This allows to write immediately the effective spin operators spanning each total spin multiplet which arises from the coupling between the ions. Explicit formulas for the recurrently encountered cases of pairs where S1 = S2 = 3/2 or S1 = 5/2 and S2 = 1/2 or S1 = 1 and S2 = 1/2 are deduced. Some salient features of these, concerning the second-order contributions to the zero-field splitting, are discussed in the light of available experimental data. The conclusions drawn seems to encourage a more extensive use of the model.