Intrinsic damping and intentional ferromagnetic resonance broadening in thin Permalloy films

Detailed ferromagnetic resonance measurements on thin Ni80Fe20 films are described that determine characteristics of intrinsic damping and the effects of intentionally created defects on linewidth. Measurements are made as a function of frequency with magnetization oriented in-plane and normal to the plane. For nominally uniform films, the ferromagnetic resonance linewidth is linear in frequency for both in-plane and normal magnetization and is well described by Landau-Lifshitz damping with a constant damping parameter. The effect of inhomogeneity was investigated by depositing the Ni80Fe20 films on specially prepared substrates, one with parallel, random grooves and one with polycrystalline, antiferromagnetic NiO. The linewidth in these samples is generally larger with magnetization in-plane than it is with magnetization normal. In the NiO/Ni80Fe20 film, the in-plane linewidth is linear in frequency with a significant zero-frequency linewidth. In the Ni80Fe20 sample on the grooved substrate, the linewidth has a more complicated frequency dependence. (C) 2003 American Institute of Physics.