  The detailed theoretical understanding of quantum spin dynamics in various
molecular magnets is an important step on the roadway to technological
applications of these systems. Quantum effects in both ferromagnetic and
antiferromagnetic molecular clusters are, by now, theoretically well
understood. Ferromagnetic molecular clusters allow one to study the interplay
of incoherent quantum tunneling and thermally activated transitions between
states with different spin orientation. The Berry phase oscillations found in
Fe_8 are signatures of the quantum mechanical interference of different
tunneling paths. Antiferromagnetic molecular clusters are promising candidates
for the observation of coherent quantum tunneling on the mesoscopic scale.
Although challenging, applications of molecular magnetic clusters for data
storage and quantum data processing are within experimental reach already with
present day technology.
