  In this work we deal with doubly decorated Ising-Heisenberg models on planar
lattices. Applying the generalized decoration-iteration transformation we
obtain exact results for the antiferromagnetic version of the model. The
existence of a new quantum dimerized phase is predicted and its physical
properties are studied and analyzed. Particular attention has been paid to the
investigation of the phase boundaries, pair-correlation functions and specific
heat. A possible application of the present work to some molecular magnets is
also drawn.
