Investigation on peak frequency of the microwave absorption for carbonyl iron/epoxy resin composite

Microwave absorbing characteristics of carbonyl iron/epoxy resin composite with various volume concentrations were investigated in 0.1-18 GHz. According to the electromagnetic parameters and thicknesses of the sample, numerical calculation and experiment have demonstrated that the frequency dependence of the microwave absorption comply with the quarter-wavelength (λ/4) matching model that may explain not only the peak frequency but also the number of the peaks. It implies that the quarter-wavelength condition can be successfully applied to understand and predict the peak frequency of the microwave absorption for ferromagnetic metal-based composites. - Research highlights: → The dip in RL complies with the quarter-wavelength condition. → Two dips appear simultaneously when the sample thickness is thicker than the critical thickness tc3/4. → The peak frequency of the dips can be manipulated by changing the sample thickness.