Bias Magnetic Field Dependence of RF Permeability in Thin Permalloy Films

Abstract

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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RF</sub> ) 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RF</sub> assumed to be sufficiently small compared with the anisotropic field H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</sub> , 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.