The influence of local distortions on the static and dynamic properties of copper and silver eightfold-coordinated Jahn-Teller complexes in mixed crystals with a fluorite-type structure

The influence of local distortions on the structure and properties of copper and silver impurity Jahn-Teller complexes in mixed crystals, namely, Ca_xSr_1?x F₂: Me ²⁺ and Sr_1?x Ba_xF₂: Me ²⁺ (0≤x≤1, Me ²⁺=Cu²⁺ or Ag²⁺), is investigated using electron paramagnetic resonance (EPR) spectroscopy at frequencies of 9.3 and 37 GHz in the temperature range 4.2–250 K. Local distortions of the tensile and compressive types are induced by Ca²⁺, Sr²⁺, and Ba²⁺ impurity ions incorporated into the first or second coordination sphere of the cationic environment of the Me ²⁺ impurity ion during crystal growth.