  Using micron-sized thermometers and Hall bars, we report time-resolved
studies of the local temperature and local magnetization for two types of
magnetic avalanches (abrupt spin reversals) in the molecular magneti
Mn12-acetate, corresponding to avalanches of the main slow-relaxing crystalline
form and avalanches of the fast-relaxing minor species that exists in all
as-grown crystals of this material. An experimental protocol is used that
allows the study of each type of avalanche without triggering avalanches in the
other, and of both types of avalanches simultaneously. In samples prepared
magnetically to enable both types of avalanches, minor species avalanches are
found to act as a catalyst for the major species avalanches. magnetically to
enable both types of avalanches, minor species avalanches are found to act as a
catalyst for the major species avalanches.
