  The magnetization dynamics equation predicts that a domain wall that changes
structure should undergo a displacement by itself - automotion - due to the
relaxation of the linear momentum that is associated with the wall structure.
We experimentally demonstrate this effect in soft nanostrips,transforming under
spin transfer torque a metastable asymmetric transverse wall into a vortex
wall. Displacements more than three times as large as under spin transfer
torque only are measured for 1~ns pulses. The results are explained by
analytical and numerical micromagnetics. Their relevance to domain wall motion
under spin transfer torque is emphasized.
