Thermal Control of the Intrinsic Magnetic Damping in a Ferromagnetic Metal

We report experiments on the control of intrinsic magnetic damping by thermal torque effects produced by the spin Seebeck effect and the anomalous Nernst effect in a thin layer of a ferromagnetic metal (Permalloy (Py), ${\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}$). Damping is measured in ferromagnetic resonance (FMR) experiments on a sample excited by microwave radiation and detected by the dc-voltage-generated spin rectification and magnonic charge pumping in the Py film. Application of a temperature gradient in the longitudinal configuration increases or decreases the dc-voltage line width, depending on the sign of the thermal gradient, demonstrating that the magnetic damping in Py is controlled by currents generated by thermal effects. The absolute values of the line-width changes in Py may reach 1 order of magnitude larger than in the ferrimagnetic insulator yttrium iron garnet. The large change in magnetic damping is interpreted as a superposition of different phenomena in the same metallic ferromagnet.