  By means of Dynamical Mean-Field Theory we investigate the spin response
function of a model for correlated materials with d- or f-electrons hybridized
with more delocalized ligand orbitals. We point out the existence of two
different processes responsible for the dynamical screening of local moments of
the correlated electrons. Studying the local spin susceptibility we identify
the contribution of the "direct" magnetic exchange and of an "indirect" one
mediated by the itinerant uncorrelated orbitals. In addition, we characterize
the nature of the dynamical screening processes in terms of different classes
of diagrams in the hybridization-expansion contributing to the density-matrix.
Our analysis suggests possible ways of estimating the relative importance of
these two classes of screening processes in realistic calculations for
correlated materials.
