Analysis of trigonal distortions in Cs₂Na(Al, Ga)F₆:Cr³⁺ using experimental EPR data

Using the latest experimental data on electron paramagnetic resonance (EPR) measurements for the Cr³⁺ centers in Cs₂Na(Al, Ga)F₆ crystals we derive from the values of the trigonal field parameters, the angles between the C₃ axis and Cr³⁺ - F^- chemical bonds and relate the signs of the trigonal field parameters to the character of the trigonal deformation. The spin Hamiltonian (SH) parameters (zero-field splitting D, anisotropic g factors g∥ and g⊥) for trigonal Cr³⁺ centers in Cs₂Na(Al, Ga)F₆ are theoretically investigated by using the perturbation formulas for a 3d³ ion in a trigonal symmetry. The calculated SH parameters based on the local geometry are in good agreement with those deduced from the experimental EPR measurements.