Self-consistent determination of the key spin-transfer torque parameters from spin-wave Doppler experiments

Current-induced magnetization dynamics is governed by a subtle combination of damping, adiabatic, and nonadiabatic spin-transfer torques (STTs). A precise determination of these three key parameters is difficult since they have to be determined in the very same nanostructured sample. In this study, we experimentally determine the spin-tansfer torque parameters in a fully self-consistent approach by optically accessing current-induced spin-wave dynamics. Our technique allows a precise access to spin-wave characteristics and their current-induced changes, especially the change in decay length which carries the information about the nonadiabaticity. Accessing this quantity allows the implementation of an analytical model which leads to a direct and separate extraction of the three STT key parameters without resorting to micromagnetic simulations.