Contents I. Introduction
The technological development of ferromagnetic amorphous films is motivated essentially by their high frequency magnetic applications seeing that the highest susceptibility is required in the gigahertz range. Because of the moderate saturation magnetization combined with a weak magnetic anisotropy, soft amorphous alloys are also of great interest in the growing field of the electronic article surveillance. However, the maximum useful thickness of the layer is limited by the skin depth for which the eddy current induced damping drops off their performance. Dynamic magnetic anisotropy under a static magnetic field is considered as an outstanding tool to analyze these materials [1]–[3]. It is commonly observed that transverse biased susceptibility differs for to the theoretical predictions given by the Stoner-Wohlfarth (S-W) model considering a single anisotropy [4], [5]. This discrepancy between experimental and theoretical results is generally ascribed to the magnetization ripple effect [6]. Magnetic anisotropy dispersion also influences strongly the magnetic response of the polycrystalline films and the amorphous films [7], [8]. Internal stress via the magneto-elastic coupling and the demagnetizing field behave as potential sources of dispersion modifying the anisotropy fields distribution across the thickness or over the film plane. Magnitude distribution of the magnetic anisotropy was already calculated from the magnetization curve along the hard axis [9]. It has also been suggested a manner to determine anisotropy dispersion including orientation distribution using a biaxial VSM [10] in order to calculate the high frequency permeability for some soft amorphous films. Nevertheless, the exchange energy term was always neglected in all these works.
