Spin-Wave versus Joule Heating in Spin-Hall-Effect/Spin-Transfer-Torque Driven Cr/Heusler/Pt Waveguides

We present a time-resolved study of the DC-current driven magnetization dynamics in a microstructured Cr/Heusler/Pt waveguide by means of Brillouin light scattering. A reduction of the effective spin-wave damping via the spin-transfer-torque effect leads to a strong increase in the magnon density. This is accompanied by a decrease of the spin-wave frequencies. By evaluating the time scales of these effects, we find that the frequency shift can be attributed to a heating of the magnetic layer. Further investigations reveal that this heating is dominantly caused by the decay of spin waves which is accompanied by a flow of energy from the spin-wave system to the phonon system. In contrast, Joule heating due to the electric current and nonlinear effects only play a minor role. The results show that in any magnetic system which is strongly excited by the spin-transfer-torque effect the contribution to the temperature increase by an increased magnon density needs to be considered.