  Non-equilibrium spin transport in a magnetic tunnel junction comprising a
single magnetic layer in the presence of interfacial spin-orbit interaction
(SOI) is studied theoretically. The interfacial SOI generates a spin torque of
the form {\bf T}=T_{||}{\bf M}x({\bf z}x{\bf M})+T_{\bot}{\bf z}x{\bf M}, even
in the absence of an external spin polarizer. For thick and large tunnel
barriers, the torque reduces to the perpendicular component, $T_{\bot}$, which
can be electrically tuned by applying a voltage across the insulator. In the
limit of thin and low tunnel barriers, the in-plane torque $T_{||}$ emerges,
proportional to the tunneling current density. Experimental implications on
magnetic devices are discussed.
