  We consider dc-electronic transport through a nanowire suspended between
normal- and spin-polarized metal leads in the presence of an external magnetic
field. We show that magnetomotive coupling between the electrical current
through the nanowire and vibrations of the wire may result in self excitation
of mechanical vibrations. The self-excitation mechanism is based on
correlations between the occupancy of the quantized electronic energy levels
inside the nanowire and the velocity of the nanowire. We derive conditions for
the occurrence of the instability and find stable regimes of mechanical
oscillations.
