About the Electromagnetic Properties of the Thin Films of Zinc Metaferrites in Microwave Range

A particular category of metamaterials were studied in this paper: the metaferrites. We have considered the nanocrystalline thin films of zinc meta-ferrite. The material is paramagnetic in the bulk form, but becomes ferrimagnetic in thin film format (of tens of nanometers thick). In plus, one obtains a tunable structure because the electromagnetic parameters of the thin film (permittivity, resistivity, permeability) change when Zn/Fe ratio varies and, in the same time, the spontaneous magnetization presents a strong dependence on the grain size, dropping sharply for larger grains. The metaferrite film is recommended for RF and microwave applications, but its complex electric permittivity and magnetic permeability determinations are necessary. We have performed these determinations by structural simulation with the HFSS program by Ansoft, in microwave range (8 - 15 GHz), where the experimental results are incomplete, using a proper algorithm and our previous experience in metamaterials study. The range of the results indicates a permittivity around 15, dependent on Zn content, frequency and temperature and a real permeability up to 60, dependent on grain size, f and T, in the considered frequency range, above to the ferromagnetic resonance which occurs at 6-7 GHz. By comparison with the punctual experimental results, the errors of the method seem not to exceed 4 %.