The studies of high-frequency magnetic properties and absorption characteristics for amorphous-filler composites

•Prepare amorphous flake composite with core–shell (ferrite nanoparticle) structure.•Permittivity is greatly decreased for composites with core–shell-like structure•Absorption properties are improved due to greatly decreased permittivity.•The absorption has its origin in the quarter-wavelength resonator.•The calculated fAfA and RLRL are well consistent with the observed results.

Pure amorphous flake fillers and amorphous flakes coated by ferrite nanoparticles with core–shell-like structure were fabricated using mechanical ball-milling. The later with core–shell-like structure can greatly decrease permittivity and improve the absorption properties, as compared to the former. The absorption of all amorphous-filler composites has its origin in a quarter-wavelength resonator. Based on the resonator model, absorption frequency fA and the corresponding return loss RL are calculated, which are well consistent with observed values. It is also found that the resonance frequency is proportional to effective resistivity, based on William–Shockley–Kittel's eddy model.