Spin-orbit precession effect in a Py/Pt/Co tri-layer structure detected by ferromagnetic resonance

Spin-orbit torques (SOTs) acting in a Py/Pt/Co tri-layer, where the Py and Co layers are in-plane and perpendicularly magnetized, respectively, are investigated via the ferromagnetic resonance method. The resonance linewidth of the Py layer is clearly modulated by the DC bias current due to the damping-like SOT originated from the spin Hall effect in the Pt. In addition to this, the linewidth modulation efficiency is found to depend on the magnetization polarity of the perpendicularly magnetized Co layer. We conclude that this behavior comes from an additional damping-like SOT originating from the spin-orbit precession effect at the Pt/Co interface.