Tetragonal distortions of the octahedral environments of Cr³⁺, Fe³⁺ and Gd³⁺ ions in A₂CdF₄ (A = Rb, Cs) and ACdF₃ crystals

Abstract

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.

Keywords:

• Electron paramagnetic resonance
• Local structure
• Crystal-field theory
• Superposition model
• Cr³⁺
• Fe³⁺
• Gd³⁺
• A₂CdF₄ (A = Rb, Cs)
• ACdF₃