Bias Magnetic Field Dependence of RF Permeability in Thin Permalloy Films

Dependence of RF permeability (μRF = μ'RF - j μ''RF) on a bias magnetic field (H: corresponding to a signal field) in a permalloy film, when H and RF exciting magnetic fields (H
_RF
) are in the direction of the hard axis in Permalloy films, was analyzed with the film taken as a single domain, the demagnetizing field in the film plane taken as 0, H
_RF
assumed to be sufficiently small compared with the anisotropic field H
_K
, and H assumed to be static. It was found that the μ'RF change is sharp at ω < ωK (ωß: ferromagnetic resonance frequency at H = 0) and the μ''RF change is sharp at ω ≃ ωK.