Complex Permeability and Permittivity Variation of Radar Absorbing Materials Based on MnZn Ferrite in Microwave Frequencies

The complex dielectric permittivity (epsilon) and magnetic permeability (mu) of Radar Absorbing Materials (RAM) based on magnetic particles (MnZn ferrite particles) embedded in a dielectric matrix (silicon rubber) have been studied in the frequency range of 2 to 18 GHz. The relative permeability and permittivity of MnZn ferrite-silicon composites for various mass fractions are measured by the transmission/reflection method using a vector network analyzer. The concentration dependence of permittivity and permeability on the evaluated frequency range is analyzed. In a general way, the results show epsilon' parameter presenting more significant variation among the evaluated parameters (epsilon '', mu '', mu ''). The comparison of dielectric and magnetic loss tangents (epsilon ''/epsilon' and mu ''/mu', respectively) shows more clearly the variation of both parameters (epsilon and mu) according to the frequency. It is also observed that higher MnZn ferrite content fractions favor both dielectric and magnetic loss tangents.