Microwave complex permeability of planar anisotropy carbonyl-iron particles

Planar anisotropy carbonyl-iron (PACI) particles were prepared from sphere-shaped carbonyl-iron (SSCI) materials by a simple ball milling technique. The frequency-dependent complex permeability of paraffin composites with 50% volume concentration of particles has been investigated in 0.1–18 GHz frequency range. The as-milled PACI composites show a dramatic enhancement of complex permeability and a higher resonance frequency compared with SSCI composite. This is due to the PACI particles, which have an easy magnetization plane and a thickness smaller than their skin depth, suppressing the eddy current effects. Furthermore, the complex permeability is further improved after the PACI composite was rotationally orientated in an external magnetic field. The real permeability of oriented PACI composite reaches a large value of approximate 10.5 at 0.1 GHz, and the resonance frequency shifts to a higher frequency range.