Newly-developed magnetic responsive polymer nanocomposites were elaborated using low complexity equipments and low-cost lab materials and apparatus. Sub-10nm CoFe2O4and Fe3O4 nanoparticles with tightly controlled size distribution were synthesized using a chemical co-precipitation procedure, which involves Iron and Cobalt salts and oleic acid and oleylamine as surfactants. This polymer nanocomposite is dissolved in hexane together with calculated amount of surfactant-coated nanoparticles to obtain the polymer nanocomposites with uniform nanoparticle dispersion at desired concentration. Excellent dispersion of magnetic nanoparticles in the polymer matrix is very important for a low-loss material at microwave and RF frequencies, as it minimizes magnetic hysteresis losses by reducing magnetic coupling amongst particles.The amount and composition of all the constituent solvents is critically-controlled for the purpose of maintaining the desired viscosity to control the exact thickness of the thin film after solvent evaporation and the curing process.

The electrical microwave properties of Fe3O4-based polymer nanocomposites (e.g., permeability, permittivity and loss tangent) were tuned under externally-applied DC magnetic fields. In addition, two novel microstrip-based test structures were used to extract the complete set of microwave properties and their dependence on externally-applied magnetic field. The transmission of microwave signals through these structures is susceptible to variation in the dielectric/magnetic properties of the polymer nanocomposites, which facilitates the demonstration of the tunability and extraction of properties at different magnetic field strengths.

The required magnetic field is achievable by small commercial permanent magnets, which justifies the use of this new class of materials for implementation of practical microwave and RF devices and circuits. Magnetic polymer nanocomposites are very easy to process, which enables them to be employed in both PCB board and chip levels using conventional manufacturing processes. They exhibit unique and very attractive properties for many microwave applications that require tunability and flexible materials.