Detection of torque effects in Co/Pt via ferromagnetic resonance

Charge-current-induced torque effects on the magnetization dynamics of ferromagnetic/metal bilayer is interesting from the aspect of fundamental physics as well as the applications in spintronic devices. The torque-induced variation of damping constant of magnetization can be foreseen from the change of the linewidth of ferromagnetic resonance spectrum. The Oersted torque (tau Oe) and current-induced torque (tau C) are induced by charge current; while the spin-orbit torque (tau SO) and field-like torque (tau FL) are induced by spin current. However, the torque effects often were hindered due to the heating-induced artifacts. In this work, we particularly pay attention to minimize the Joule heating effects in order to investigate the intrinsic torque effects in cobalt (Co)/platinum (Pt) bilayer with an applied charge current ranging from -60 to 60 mA. In this range, the Oersted field is estimated as 0.25 Oe which is much smaller than the experimental result of Delta Hr (similar to 0.7 Oe), implying some contribution from the spin-current induced field like torque. The current-polarization-induced asymmetry of linewidth Delta W, Delta W equivalent to W+Jc-W-Jc, increases from 0 to 0.15 with Jc changing from 0 to 60 mA, which is attributed to the spin-orbit torque.