Magnetic avalanches in molecular nanomagnets

摘要

The magnetization of the prototypical molecular magnet Mn _(12)-acetate exhibits a series of sharp steps at low temperatures due to quantum tunneling at specific resonant values of magnetic field applied along the easy c-axis. An abrupt reversal of the magnetic moment of such a crystal can also occur as an avalanche, where the spin reversal proceeds along a "deflagration" front that travels through the sample at subsonic speed. In this article, we review experimental results that have been obtained for the ignition temperature and the speed of propagation of magnetic avalanches in molecular nanomagnets. Fits of the data with the theory of magnetic deflagration yield overall qualitative agreement. However, numerical discrepancies indicate that our understanding of these avalanches is incomplete.