Exchange constants and transfer integrals of spinel ferrites

We have studied Fe3O4, CoFe2O4, NiFe2O4 and CuFe2O4 considering Neel's two-sublattice collinear model and the superexchange theory. We have found that, for this theory to be valid, the interaction between ions in tetrahedral sites should be very weak, and we have proposed a model to find the constants J(AB) and J(BB) with the assumption that J(AA) = 0. Using this model, the calculated values of these constants follow the expected tendencies for the four systems under study, as well as the ion-to-ion constants of Anderson's theory which we obtained through the assessment of the transfer integrals.