  We have examined the spin polarization of the electron current in a
ferromagnetic metal induced by the spin-dependent surface screening at the
dielectric-ferromagnetic metal (D-FM) interface. In an applied ac voltage, the
dynamic band splitting driven by the changes in the screening charge at the
D-FM interface develops spin accumulation. The resultant spin accumulation
gradient produces a time-dependent spin current. We have derived the rate of
the spin accumulation on the rate of the screening charge density accumulation
within the Stoner band model. The spin-charge dynamics in the system is then
modeled by a set of diffusive equations with the contributions from
spin-dependent surface screening ands spin-dependent conductivity. We show for
MgO-Cu-Co-MgO system that the spin-dependent screening in thin Co film produces
spin accumulation 7 times higher than that obtained by the spin-dependent
conductivity in thick Co films. We propose an experimental approach to validate
our numerical predictions and to distinguish between spin accumulation induced
by the spin-dependent conductivity and by the spin-dependent surface screening.
