Ferromagnetic resonance study of thickness-dependent magnetization precession in Ni80Fe20 films

Abstract

The ferromagnetic resonance (FMR) behaviors for Ni80Fe20 Permalloy films with a wide thickness range from 30to360nm were investigated. The FMR measurements were performed by a vector network analyzer (VNA) technique with scanning frequency at a specified external field. The measured frequency response was fitted well by the theoretical precession conditions. The FMR results show that the effective saturation magnetization, μ0Meff, increases from 1.01to1.36T, while the film thickness varies from 30to360nm. A discontinuous transition is observed at the thickness of 90nm, which corresponds to the transformation boundary of domain wall from Néel to Bloch type in Permalloy films. Meanwhile, the variation of damping coefficient with film thickness also shows a discontinuity at 90nm. For films thinner than 90nm, the dampings vary insignificantly with film thickness. For films thicker than 90nm, the damping coefficient varies linearly with the thickness. The result could be explained by the magnon scattering through nonuniform magnetization.