Tetragonal distortions of the octahedral environments of Cr3+, Fe3+and Gd3+ions in A2CdF4(A = Rb, Cs) and ACdF3crystals

The tetragonal distortions of local octahedral environments of Cr3+, Fe3+ and Gd3+ ions in Rb2CdF4, Cs2CdF4, RbCdF3 and CsCdF3 crystals have been studied by analyzing their EPR spectra. From the studies, it is found that the tetragonal distortions for Cr3+ and Fe3+ impurity ions, which substitute Cd2+ and have nearly the same ionic radius, are close to each other, whereas that for Gd3+ impurity ion, having a larger ionic radius, is larger than those for Cr3+ and Fe3+ ions in the same crystal. It appears that not only the impurity-ligand distance, but also the tetragonal distortions of impurity centres in crystals are closely related to the size of impurity.