Studies on the local structures and the spin Hamiltonian parameters for Fe in CdX (X = S, Se, Te).

The improved perturbation formulas of the spin Hamiltonian parameters (zero-field splittingDandgfactors) for a 3d5ion in trigonally distorted tetrahedra are constructed from the cluster approach by including both the crystal-field and charge-transfer contributions. These formulas are applied to the studies of the local structures and the electron paramagnetic resonance (EPR) spectra for Fe3+in CdX (X = S, Se, Te). The impurity Fe3+is found not to occupy exactly the host Cd2+sites but to experience the small outward shifts 0.014 and 0.006 Å away from the ligand triangles along the C3axis in CdS and CdSe, respectively. The charge-transfer contributions to the spin Hamiltonian parameters are important and increase significantly with increasing atomic number of the ligand (i.e., S2−< Se2−< Te2−) arising from the decreases of charge-transfer energy levels and the increases of ligand spin–orbit coupling coefficients. The results are discussed. [ABSTRACT FROM AUTHOR]