High-frequency Properties of Sub-micron-sized Fe-Co Particles

We report the high-frequency properties of sub-micron-sized Fe-Co particles synthesized with a polyol process, and what influence hard magnetic and non-magnetic oxide layers had on those high-frequency properties. The Fe-Co particles exhibited a resonance peak in the range of a few gigahertz, and the resonance peak shifted to a higher region for decreasing particle size. Furthermore, the presence of a multi-resonance peak in the gigahertz range was recorded. The permeability of surface-oxidized particles decreased and the resonant frequency shifted to a higher region for increasing CoFe2O4 layer thickness on the surface of the particles. However, SiO2 coating did not influence the resonant frequency even though the permeability decreased due to the decrease in the volume fraction of FeCo particles in the sample.