  We investigate the current-driven magnetization dynamics in narrow Permalloy
wires by means of Lorentz microscopy and electron holography. Current pulses
are found to transform the magnetic structure in the uniformly magnetized state
below the Curie temperature. A variety of magnetic states including reversed
magnetic domains are randomly obtained in low probability. The dynamics of
vortices found in most of observed magnetic states seems to play a key role in
triggering the magnetization reversal.
