Abstract
The individual ligand contributions to the dominant (quadrupole) component of the Gd3+ ground state splitting for nine compounds with zircon structure are determined. The results of this analysis show that the theoretical problems previously encountered in explaining the ground state splitting were due to an incorrect assumption about the relative sign of the crystal field and spin-Hamiltonian quadrupole contributions. It is argued that three basic mechanisms make contributions of a similar magnitude to the observed splitting.