Analysis of the initial complex permeability versus frequency of soft nanocrystalline ribbons and derived composites

We measured the complex permeability versus frequency between 10 kHz and 1 GHz of a soft nanocrystalline magnetic material (Finemet composition). We characterised both ribbon (20 μm thickness, 10 mm width) and composites made from particles obtained by grinding and mixed with an epoxy resin. We analyse the magnetisation mechanisms responsible for the frequency behaviour of the permeability according to the samples preparation. The composite materials have a much lower permeability and higher resonance-relaxation frequency. We show that the eddy current model is not sufficient to explain the decrease of permeability at high frequency for both the ribbon and the composites