Unconventional non-monotonic oscillations of magnetic damping in a ferromagnet/non-magnet heterostructure

Abstract

Thickness dependent quantum effects on magnetization dynamics in thin films are of paramount interest in low dimensional physics. Theoretical predictions suggest quantization driven thickness dependent oscillations in magnetic damping of ferromagnetic (FM) films. Here we demonstrate non-monotonic oscillatory variation of magnetic damping with a change in the thickness of the FM layer in a ferromagnet/non-magnet heterostructure of CoFe/Ta thin films. The thickness of the ferromagnetic CoFe layer is found to change by about two monolayers between successive high and low values of magnetic damping. The oscillation in the magnetic damping values is found to decay with the increase in the thickness of the FM layer. Furthermore, using dichroic hard X-ray photoemission, spin sensitive electronic structure measurements are performed on these thin films. The results show periodic enhancement and reduction of the spin scattering phase space with the change in the ferromagnetic layer thickness. This reveals the correlation between the periodic variation of magnetic damping and the spin-dependent electronic scattering in magnetic thin films.