Millimeter Wave Resistance of Metal-Dielectric $\text{Co}_{\rm x}(\text{SiO}_{2})_{\rm{1-x}}$ and $\text{Co}_{\rm x}(\text{Al}_{2}\text{O}_{3})_{\rm{1-x}}$ Films

Transmission and reflection of millimeter waveband electromagnetic waves have been studied for thin-film metal-dielectric $\rm Co_{x}(SiO_{2})_{1-x}$ and $\rm Co_{x}(Al_{2}O_{3})_{1-x}$ nanocomposite materials, where cobalt nanoparticles are placed inside $\rm SiO_{2}$ or $\rm Al_{2}O_{3}$ films of 100 nm thickness. The microwave properties of the nanocomposite samples with different cobalt content have been measured in the frequency ranges from 26 to 38 GHz and from 53 to 77 GHz. Frequency dependencies of transmission and reflection coefficients have been measured. Power loss in the samples has been determined. An algorithm for recovering the conductivity from the frequency dependencies of the transmission and reflection coefficients has been worked out. It has been found that the microwave conductivity increases with increasing cobalt content and differs drastically from the dc conductivity. The obtained results have been compared to the actual measurements of magnetic properties.