Nonlinear Control of Damping Constant by Electric Field in Ultrathin Ferromagnetic Films

The performances of many spintronic devices are governed by the damping constant and magnetic anisotropies of constituent materials. Spin-orbit coupling (SOC) plays a key role and is at the origins of these material parameters. Electric field control of magnetic anisotropy is in high demand for developing energy-efficient nanoscale spintronics devices. Although electric field control of interfacial magnetic anisotropies is well studied and understood, the damping constant, on the other hand, is conventionally controlled by current-induced spin-orbit torque. Here, we use an alternative approach to demonstrate nonlinear control of the damping constant in ultrathin ferromagnetic films by an electric field. We explicitly show that the presence of the Rashba SOC at a ferromagnet-insulator interface and the electric field dependence of the Rashba coefficient may account for the observed nonlinear behavior. Furthermore, we show that engineering of the underlying and oxide material properties, i.e., bulk SOC and Rashba SOC, to tune the spin angular momentum relaxation pathways, can possibly increase the device functionality significantly.