Synthesis and characterization of low-loss Fe3O4-PDMS magneto-dielectric polymer nanocomposites for RF applications

This paper presents the methodologies for synthesis and characterization of a new class of low loss Fe₃O₄-PDMS polymer nanocomposites, which exhibits well-tailored magneto-dielectric properties. Single crystalline Fe₃O₄ nanoparticles with a small size distribution of 7.5 ± 2nm were prepared by chemical precipitation method to retain the superparamagnetic characteristics and the Fe304-PDMS nanocomposites with uniformly dispersed Fe₃O₄ nanoparticles at three different loading concentrations of 80 wt%, 50 wt%, and 30 wt% were explored. Room-temperature magnetization measurements were conducted for the plain Fe₃O₄ nanoparticles and these Fe₃O₄-PDMS nanocomposites using a physical properties measurement system (PPMS) while extraction of microwave properties in wide range frequencies between 1GHz and 8GHz under different levels of externally applied magnetic field was performed by using a custom-built transmission line test fixture. The 80 wt% Fe₃O₄-PDMS nanocomposites under 0.37T of biasing field have exhibited coveted magneto-dielectric properties at 4GHz, by showing an equal-valued relative permittivity ε_r and relative permeability μ_r of 3.0. It is worthwhile mentioning that the peak relative permeability of 3.55 along with fairly low dielectric and magnetic loss tangents less than 0.02 were obtained under 0.2T DC biasing field. These newly-characterized Fe304-PDMS nanocomposites were used for successful implementation of miniaturized patch antennas, which is going to be reported subsequently.