  We theoretically study the influence of a predominant field-like spin-orbit
torque on the magnetization switching of small devices with a uniform
magnetization. We show that for a certain range of ratios (0.23-0.55) of the
Slonczewski to the field-like torques, it is possible to deterministically
switch the magnetization without requiring any external assist field. A precise
control of the pulse length is not necessary, but the pulse edge sharpness is
critical. The proposed switching scheme is numerically verified to be effective
in devices by micromagnetic simulations. Switching without any external assist
field is of great interest for the application of spin-orbit torques to
magnetic memories.
