  Current-voltage characteristics of a spintromechanical device, in which
spin-polarized electrons tunnel between magnetic leads with anti-parallel
magnetization through a single level movable quantum dot, are calculated. New
exchange- and electromechanical coupling-induced (spin-polaronic) effects that
determine strongly nonlinear current-voltage characteristics were found. In the
low-voltage regime of electron transport the voltage-dependent and exchange
field-induced displacement of quantum dot towards the source electrode leads to
nonmonotonic behavior of differential conductance that demonstrates the lifting
of spin-polaronic effects by electric field. At high voltages the onset of
electron shuttling results in the drop of current and negative differential
conductance, caused by mechanically-induced increase of tunnel resistivities
and exchange field-induced suppression of spin-flips in magnetic field. The
dependence of these predicted spin effects on the oscillations frequency of the
dot and the strength of electron-electron correlations is discussed.
