Frequency-dependent complex permittivity and permeability of iron-based powders in 2–18 GHz

A novel approach is presented to investigate the complex permittivity (ε′−jε″) and permeability (μ′−jμ″) of iron-based powders in the frequency range of 2-18 GHz. The effective permeability and permittivity of carbonyl iron-epoxy composites for various volume fractions are measured by using the transmission/reflection method. A genetic algorithm is implemented with four nonempirical effective medium theories to obtain the complex permittivity and permeability of the carbonyl iron powders in the corresponding frequency range. The use of the extracted permittivity and permeability of the carbonyl powders with Looyenga’s formula fit the experimental data well not only over a wide range of frequencies but also various concentrations of carbonyl iron.