Аннотации:
The zero-field splitting of the S state due to the virtual electron transfer processes from the ligands into an unfilled shell (ln ) of a paramagnetic ion has been calculated. A simple analytical formula has been deduced for the spin-Hamiltonian parameters. The paramagnetic centres: LiCaAlF6:Fe3+, LiSrAlF6:Fe3+, Al2O3Je3+, LiCaAlF6:Gd3+, LiSrAlF6:Gd3+, Al2O3:Gd3+ and YBa2Cu3O6+y:Gd3+ with y = 0.91, 0.95 have been considered as an example. In all cases the calculated values of the D-parameter are in agreement with the electron paramagnetic resonance data within an order of magnitude and in the sign as well.
