Investigations of the spin-Hamiltonian parameters and the tetragonal distortion due to Jahn-Teller effect for Cu2+ in trigonal CsCdCl3 and CsMgCl3 crystals

The complete high-order perturbation formulas based on a two-mechanism [i.e., crystal-field (CF) and charge-transfer (CT) mechanisms, the latter is neglected in the widely-used CF theory] model for the spin-Hamiltonian (SH) parameters (g factors g//, g⊥ and the hyperfine structure constants A//, A⊥) of d9 ions in tetragonal symmetry with the ground state |dx2-y2〉 are established. These formulas are used to the calculations of SH parameters for the tetragonal Cu2+ centers in trigonal CsCdCl3 and CsMgCl3 crystals. Form the calculations, these SH parameters are reasonably explained and the tetragonal distortions of the Cu2+ centers due to Jahn-Teller effect in both crystals are obtained. The results (including the tetragonal distortion and the relative importance of CT mechanism) are discussed.