Cobalt-polymer nanocomposite dielectrics for miniaturized antennas

Cobalt-polymer magnetic nanocomposites have been synthesized and characterized for their microstructure and properties such as permeability, permittivity, dielectric and magnetic losses from 100 MHz to 2 GHz to study their suitability as antenna dielectrics. Oxide-passivated cobalt nanoparticles were dispersed in epoxies to form nanocomposite toroids and thin-film resonator structures on organic substrates. Permeabilities of 2.10 and 2.65 were measured up to 500 MHz, respectively, with 25-nm to 50-nm and 5-nm nanoparticles in the nanocomposites. The loss tangent ranged from 0.02 to 0.04 at these frequencies. A combination of stable permeability of ∼2 at 1 GHz to 2 GHz and permittivity of ∼7 was achieved with nanocomposites having 5-nm nanoparticles. The magnetic nanomaterials described in this paper can overcome the limitations from domain-wall and eddy-current losses in microscale metal-polymer composites, leading to enhanced frequency stability. The paper also demonstrates integration of metal-polymer nanocomposites as thin-film build-up layers with two-metal-layer structures on organic substrates.