  The works on decoherence due to spin baths usually agree in studying a
one-spin system in interaction with a large spin bath. In this paper we
generalize those models by analyzing a many-spin system and by studying
decoherence or its suppression in function of the relation between the numbers
of spins of the system and the bath. This model may help to identify clusters
of particles unaffected by decoherence, which, as a consequence, can be used to
store quantum information.
