  Current-induced magnetic domain wall motion, induced by transfer of spin
transfer effect due to exchange interaction, is expected to be useful for next
generation high-density storages. We here show that efficient domain wall
manipulation can be achieved by introduction of Rashba spin-orbit interaction,
which induces spin precession of conduction electron and acts as an effective
magnetic field. Its effect on domain wall motion depends on the wall
configuration. We found that the effect is significant for Bloch wall with the
hard axis along the current, since the effective field works as $\beta$ or
field-like term and removes the threshold current if in extrinsic pinning is
absent. For N\'eel wall and Bloch wall with easy axis perpendicular to Rashba
plane, the effective field induces a step motion of wall corresponding to a
rotation of wall plane by the angle of approximately $\pi$ at current lower
than intrinsic threshold. Rashba interaction would therefore be useful to
assist efficient motion of domain walls at low current.
