Dependence of demagnetizing fields in Fe-based composite materials on magnetic particle size and the resin content

• Demagnetization factor decreases as magnetic content and particle size increases.
• Different “ideal” initial curves for each resin content due to stresses in particles.
• “Ideal” permeability rises and HC decreases as resin content and particle size rises.
• Demagnetizing fields in SMC studied by means of anhysteretic curve for the first time.

Demagnetizing fields are in general produced by the volume and surface magnetic poles. The structure of soft magnetic composite materials, where the ferromagnetic particles are insulated from each other, causes the formation of demagnetizing fields produced by the particle surfaces. These fields depend on the amount of insulation and on the shapes, clustering and distribution of ferromagnetic particles. In this work the demagnetizing fields in iron–phenolphormaldehyde resin composite samples were investigated experimentally using the method for determining the demagnetization factor from the anhysteretic magnetization curve measurement. The initial magnetization curves were calculated for an ideal composite with 100% filler content using the values of the demagnetization factor. The results on the “ideal” permeability show differences between the samples with different resin content for each granulometric class, which tells about the internal stresses introduced into ferromagnetic material during the compaction process.