  Current-induced torques in ultrathin Co/Pt bilayers were investigated using
an electrically driven FMR technique. The angle dependence of the resonances,
detected by a rectification effect as a voltage, were analysed to determine the
symmetries and relative magnitudes of the spin-orbit torques. Both anti-damping
(Slonczewski) and field-like torques were observed. As the ferromagnet
thickness was reduced from 3 to 1 nm, the sign of the field-like torque
reversed. This observation is consistent with the emergence of a Rashba spin
orbit torque in ultra-thin bilayers.
