Energy Equilibration Processes of Electrons, Magnons, and Phonons at the Femtosecond Time Scale

We relate the energy dissipation processes at the femtosecond (electron-spin relaxation time τ_el-sp) and nanosecond time scale (Gilbert relaxation τ_α) to the microscopic model proposed by Koopmans [Phys. Rev. Lett. 95, 267207 (2005)]. At both time scales, Elliot-Yafet scattering is proposed as the dominant contribution. We controllably manipulate the energy dissipation by transition metal doping (Pd) and rare earth doping (Dy) of a Permalloy film. While a change in τ_α of more than a factor of 2 is observed, τ_el-sp remains constant. We explain the discrepancies as due to relaxation channels not considered in the model.