Magnetic and electromagnetic properties of composites of iron oxide and Co–B alloy prepared by chemical reduction

Magnetic and electromagnetic properties were investigated on the composites of iron oxide and Co–B alloy, which were prepared by a modified chemical reduction method. The composites are characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometry (VSM). The complex electromagnetic parameters (permittivity εr=εr′+jεr″ and permeability μr=μr′+jμr″) of paraffin mixed composite samples (paraffin:composites=1:1 in mass ratio) were measured in the frequency range 2–18 GHz by vector network analyzer. The measured real part (εr′) and imaginary part (εr″) of the relative permittivity show two resonant peaks in the range of 2–18 GHz. The imaginary parts of relative permeability (μr″) of all samples exhibited one broad resonant peak over the 2–8 GHz range. The μr″ of samples with higher molar ratio of Co to Fe (C and D) shows negative values within 13–18 GHz, which exhibit resonant and antiresonant permeabilities simultaneously. Calculation results indicated that the reflection loss values of the composites and paraffin wax mixtures are less than −10 dB with frequency width of about 6 GHz at the matching thickness.