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 1.84mm thickness. RL values exceeding -10 dB were obtained for the absorber of 1.7mm 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.