  Very fast magnetic avalanches in (La, Pr)-based manganites are the signature
of a phase transition from an insulating blocked charge-ordered (CO-AFM) state
to a charge delocalized ferromagnetic (CD-FM) state. We report here the
experimental observation that this transition does not occur neither
simultaneously nor randomly in the whole sample but there is instead a spatial
propagation with a velocity of the order of tens of m/s. Our results show that
avalanches are originated in the inside of the sample, move to the outside and
occur at values of the applied magnetic field that depend on the CD-FM fraction
in the sample. Moreover, a change in the gradient of the magnetic field along
the sample shifts the point where the avalanches are ignited.
