Microwave magnetic properties of Co50/(SiO2)50 nanoparticles

Co50/(SiO2)50 nanoparticles were synthesized by a wet chemical method, and their microwave permeability was measured in the 0.1–18 GHz range. The synthesized nanoparticles exhibit two loss peaks at microwave frequencies: one appears around 7.0 GHz and is believed to result from the eddy current effect, the other appears around 250 MHz and is probably caused by natural ferromagnetic resonance. Compared with micrometer-size Co particles, the synthesized nanoparticles exhibit high permeability μ′ and low magnetic loss, especially over 10–18 GHz.