Synthesis and magnetic properties of Fe/SiO2 nanocomposites prepared by a sol–gel method combined with hydrogen reduction

The Fe/SiO2 nanocomposites have been prepared by a simple sol–gel method combined with hydrogen reduction. Changing the reduction temperature and the Fe cores of the as-fabricated samples are 5–10 nm and the SiO2 coating is about 0.5 nm. The real part μ′ of the permeability of the Fe/SiO2 nanoparticles is almost independent of frequencies up to at least 1 GHz and μ″ is very small. The method provides a promising route to achieve soft magnetic nanocomposite material with good soft magnetic properties, especially in the high-frequency range. The physical mechanism is related to the fact that the insulation of the SiO2 shell between particles results in an increase of the resistivity of the sample, which may reduce the effect of eddy current at high frequency, and make the real part μ′ of the permeability remain almost constant and the imaginary part very small.