  The use of magnetic nanowires as memory units is made possible by the
exponential divergence of the characteristic time for magnetization reversal at
low temperature, but the slow relaxation makes the manipulation of the frozen
magnetic states difficult. We suggest that finite-size segments can show a fast
switching if collective reversal of the spins is taken into account. This
mechanism gives rise at low temperatures to a scaling law for the dynamic
susceptibility that has been experimentally observed for the dilute molecular
chain Co(hfac)2NitPhOMe. These results suggest a possible way of engineering
nanowires for fast switching of the magnetization.
