Sustained electromagnetic properties of Ni-Zn-Co nanoferrites for the high-frequency applications

Nano nickel-zinc-cobalt ferrites of composition Ni_0.49Zn_0.49Co_0.02Fe₂O₄ were prepared by a citrate precursor method. X-ray diffraction, transmission electron microscopy and scanning electron microscopy confirmed the size, structure and morphology of the nanoferrite. After appropriate treatments, the average grains size is about 50 nm and material shows almost constant complex permeability and permittivity in the frequency range from 10 to 200 MHz, equal to ~ 9.1 + j0.51 (loss tangent ~ 0.05) and ~ 4.4 + j0.16 (loss tangent ~ 0.036), respectively. The refractive index n is close to 6.5. Relaxation phenomenon takes place above 200 MHz, an unusual value for spinel ferrites. Owing to these electromagnetic properties, Ni-Zn-Co nanoferrites should be useful for high-frequency applications.