Electron Paramagnetic Resonance Studies of Gd³⁺ in KZnF₃ and KCdF₃

Abstract

EPR investigations of Gd³⁺ impurity ions in KZnF₃ and KCdF₃ have been made at the temperatures 487, 300, 77 and 4.2 K for KZnF₃ and at 487 K for KCdF₃. The spectra for cubic symmetry have been observed and the spin Hamiltonian parameters in cubic crystalline field have been determined. At the temperature of 487 K, the fourth-order zero-field splitting parameters in the spin Hamiltonian show remarkable difference for both crystals as following values: b₄=−6.97×10⁻⁴ cm⁻¹ for KZnF₃ and |b₄|=1.6×10⁻⁴ cm⁻¹ for KCdF₃. This difference implies that Gd³⁺ impurities substitute for different cubic sites. From the size consideration of the ionic radii among K⁺, Zn²⁺, Cd²⁺ and Gd³⁺, it is concluded that Gd³⁺ substitute for 12-fold K⁺ site in KZnF₃ and 6-fold Cd²⁺ site in KCdF₃.