Magnetically Tunable Polymer Nanocomposites for RF and Microwave Device Applications

There has been much interest in polymer nanocomposites (PNC) recently due to potential applications for EMI shielding, tunable electromagnetic devices and flexible electronics. We report synthesis, structural, magnetic and RF characterization on PNCs ranging from 20-80 wt-{\%} loadings of Fe$_{3}$O$_{4}$ and CoFe$_{2}$O$_{4}$ nanoparticles ($\sim $8nm) in a thermosetting resin from the Rogers Corporation. Nanoparticles were synthesized by thermal decomposition and characterized by XRD and TEM. Magnetic properties were studied using a Quantum Design PPMS. PNCs displayed characteristic features of superparamagnetism at room temperature and blocking at low temperature. Microwave transmission/reflection studies were done using a microstrip resonator. Strong tunability in the microwave absorption was observed. We extend our study to include nanoparticle-filled multi-walled carbon nanotubes synthesized by CVD. These high-aspect ratio magnetic nanostructures, with tunable anisotropy, are of particular interest in enhancing magnetic and microwave responses in existing PNCs.