  Following the early theoretical descriptions of the spin-orbit-induced spin
torque [S.G. Tan et al., arXiv:0705.3502 (2007); S.G.Tan et al., Ann. Phys.326,
207 (2011)], the first experimental observation of such effect was reported by
L. M. Miron et al., Nature Mater, 9, 230 (2010). We present in this article
three additional spin torque terms that arise from the non-uniformity in
magnetization space of the Rashba spin-orbit effect. We propose a simple Rashba
gradient device which could potentially lower switching current by n orders of
magnitude, where large n measures a small magnetization change.
