  In this paper we calculate the block entanglement entropies of spin models
whose ground states have perfect antiferromagnetic or ferromagnetic long-range
order. In the latter case the definition of entanglement entropy is extended to
properly take into account the ground state degeneracy. We find in both cases
the entropy grows logarithmically with the block size. Implication of our
results on states with general long-range order will be discussed.
