Loss separation and thermal studies of Fe/SiO2/ferrite soft magnetic composites

Energy saving is one of the main driving forces behind the development of new magnetic materials. Among many investigated materials, soft magnetic composites (SMCs) appear as a possible concept for critical areas in modern society, including energy production and its transformation. In this paper, soft magnetic composites based on Fe/SiO2/ferrite with low energy losses and high magnetic permeability are studied. An increase of temperature in working conditions affects the magnetic properties of the SMCs, which requires considering the temperature effect in the prediction of magnetic properties. The magnetic properties in the composites with (a) 0 vol%, (b) 2 vol%, (c) 5 vol%, and (d) 10 vol% of ferrite at the peak induction of 0.1 T in the temperature range of 20–140 °C are studied. The associated loss separation as a function of ferrite content and temperature is performed. The observations are explained by the analysis of energy losses and their origin in terms of the Statistical Theory of Losses. Frequency–temperature maps of hysteresis loss and excess loss component show deeper insight into the magnetisation processes in the hybrid composite material. Further analysis of the permeability versus temperature shows a decrease in values above 125 °C, related to the Curie temperature of ferrite. In this work, very good magnetic properties of the composite with 2 vol% of ferrite are achieved with initial relative permeability μ = 84 and energy loss W = 57 J/m3 at Bp = 0.1 T and f = 35 kHz.