Magnetic properties of soft magnetic Fe@SiO2/ferrite composites prepared by wet/dry method

Abstract

The paper presents the soft magnetic composites consisting of iron particles with smoothed surfaces, coated by the two-layer insulation of SiO2 and Ni-Zn/Cu-Zn soft ferrite nano-sized grains with different content, which were prepared by the combination of wet (Stöber method) & dry (mechanofusion) particle coating process, followed by the high-pressure compaction. The total, differential and complex permeability were analysed and the energy losses were separated into DC, classical and excess losses as a function of frequency and into high and low induction losses as a function of magnetic induction. The thorough analysis of the magnetic properties as well as of the structure and electrical properties revealed the optimum ferrite content and proved the multipurpose effect of the insulation, serving as: (1) the insulator for iron particles minimizing eddy currents in composite, (2) the interparticle air gaps filler reducing inner demagnetizing fields, and (3) the magnetically active component for the magnetic flux continuity in composite material. There was a visible improvement of magnetic permeability and energy loss reduction in sample with 10 % of incorporated ferrite, i.e., the low ferrite content improved the magnetic behavior by effective coupling of Fe particles.