Microwave characterization of magnetically hard and soft ferrite nanoparticles in K-band

Nano-sized magnetic particles show great promise in improving the performance of microwave absorbers with respect to the corresponding bulk materials. In this paper, magnetically hard and soft ferrite nanoparticles (CoFe 2O 4 and Fe 3O 4) having an average size of 14 and 11 nm were prepared by co-precipitation method and characterized in terms of morphology, structure, and magnetic properties. Their permeability and permittivity were measured by a waveguide technique, embedding each sample in a host medium. Their parameters at microwave frequencies were retrieved by comparing different effective medium equations.