Electron spin echoes were obtained by performing 2-pulse and 3-pulse experiments on electron paramagnetic resonance transitions of Jahn-Teller orthorhombically distorted Cr2+ in Cr-doped samples. Particular emphasis was placed on stimulated electron spin envelope modulation. Because this system had a spin of S = 2, and the zero-field splitting contribution was of the same order of magnitude as the electronic Zeeman term, a new formalism was developed for analyzing the stimulated electron spin envelope modulation. This permitted the Mims formalism for S = ½ to be extended to more complex systems. By applying it to the present results, the superhyperfine interaction tensors of Cr2+ with the nearest-neighbor, next-nearest neighbor and third-nearest neighbor fluoride ions, were determined. The Cr2+-F- distances were estimated by using the orthogonalized envelope function method. The defect model consisted of 4 fluoride ions, in the yz (110) defect plane, which relaxed inwards to touch the Cr2+ ion. The remaining 4 fluoride ions relaxed outwards to fit into the next Sr2+ ion cage.

P.B.Oliete, V.M.Orera, P.J.Alonso: Physical Review B, 1996, 54[17], 12099-108