Microwave resonance in Fe/SiO2 nanocomposite

A broad resonance band in the 1-16 GHz range observed in Fe/SiO2 nanocomposite results from the coexsistence of natural resonance and exchange resonance. The natural resonance appears at 5.91 GHz and can be related to the core spins in the Fe nanoparticles, whereas the exchange resonance appears at 11.01 GHz and can be associated with the surface spins of the Fe nanoparticles in the Fe/SiO2 nanocomposite. Both resonance frequencies depend on the surface anisotropy of the Fe nanoparticles, which can be affected by the Fe particle size, and can be tuned by adjusting the Fe particle size.