Microwave-absorption properties of Fe(Mn)/ferrite nanocapsules

Electromagnetic (EM) wave absorption properties of the paraffin–Fe(Mn)/ferrite nanocapsule composite (with 40 wt% nanocapsules) were investigated in the 2–18 GHz frequency range. The Fe(Mn)/ferrite nanocapsules synthesized by arc-discharging have a core–shell structure with cores 10–30 nm in diameter and shells about 5 nm in thickness. The reflection loss (RL) calculated from the measured permittivity and permeability was found to exceed −20 dB in the 13–15 GHz range for a thickness of about 1.75–1.95 mm. The optimal RL is −28.2 dB at about 14 GHz with 1.84 mm thickness. RL values exceeding −10 dB were obtained for the absorber of 1.7 mm thickness in the range 12.7–17.1 GHz, which almost covered the whole Ku-band (12.4–18 GHz). The excellent EM wave absorption properties of the Fe(Mn)/ferrite nanocapsules significantly depend on the core–shell microstructure and the match of dielectric and magnetic losses.