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

Abstract

We relate the energy dissipation processes at the femtosecond (electron-spin relaxation time ${\tau }_{\mathrm{el}\mathrm{\text{−}}\mathrm{sp}}$) and nanosecond time scale (Gilbert relaxation ${\tau }_{\alpha }$) 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 ${\tau }_{\alpha }$ of more than a factor of 2 is observed, ${\tau }_{\mathrm{el}\mathrm{\text{−}}\mathrm{sp}}$ remains constant. We explain the discrepancies as due to relaxation channels not considered in the model.