The ferromagnetic damping and relaxation mechanisms of Ni80Fe20 (NiFe) films sputtered on rippled Al2O3 substrates were investigated by in-plane angular dependence ferromagnetic resonance (FMR) measurements where these rippled Al2O3 substrates were prepared by thermal annealing. The linewidth of intrinsic contribution due to Gilbert damping mechanism and linewidth of extrinsic contribution related to two-magnon scattering (TMS) and inhomogeneous broadening of films were identified by filtering different magnetic relaxation mechanisms of films. The results show that the magnitude of ferromagnetic damping of films deposited on rippled Al2O3 substrates can be manipulated by modifying the ripple morphology of substrates and it is strongly dependent on the angle between the direction of the ripple and the external field. The non-Gilbert-type damping for these films is an adjustable, anisotropic contribution to the overall relaxation. The two-magnon scattering and inhomogeneous broadening act as non-Gilbert damping mechanism in magnetization relaxation and they dominate the variation of total linewidth. This work revealed the tunable magnetization relaxation in films deposited on rippled Al2O3 substrates with different surface morphology formed by annealing and it would be helpful for utilizing these rippled substrates to design magnetization relaxation characteristics of spintronic and magnonic devices. (C) 2021 Elsevier B.V. All rights reserved.
Key words
Magnetic thin films/Ferromagnetic resonance linewidth/Magnetization relaxation/Rippled sapphire substrates/THIN-FILMS/INTERPLAY
NSTL
Elsevier