Explanations of the EPR parameters for the rhombic Cr3+-VM and Cr3+-Li+ centers in A2MF4 (A = K, Rb, Cs; M = Mg, Zn, Cd) crystals

In this paper, we establish the high-order perturbation formulas of EPR zero-field splittings D, E and g factors, g(x), g(y) and g(z) for 3d(3) ions in a sort of rhombic symmetry where the symmetry axes and hence the crystal-field axes lie along the [001], [010] and [100] axes. From these formulas, the EPR parameters D, E, g(x), g(y) and g(z) for the rhombic Cr3+-V-M and Cr3+-Li+ defect centers in the tetragonal A(2)MF(4) (A = K, Rb, Cs; M = Mg, Zn, Cd) fluorides are calculated by considering the suitable defect-induced lattice distortions. The results are in reasonable agreement with the observed values.