Complex permeability spectra of permendur composite materials

Complex permeability μ* and permittivity ε* spectra of permendur (Co50Fe50) composite materials have been studied in the microwave frequency range considering the application to the left-handed meta-materials and EMC devices. High surface electrical resistance of the permendur particles was achieved by the heat-treatment in order to suppress the eddy current effect in the high particle content composites. For the 82.6 vol.% composite, the μ' is 11 and less than 1 at 100 MHz and 6 GHz, respectively; the μ'' shows the two peaks around 700 MHz and 3GHz due to the domain wall and gyromagnetic spin resonance. On the other hand, the ε' is almost constant value of 28 and the ε'' is almost zero in the frequency range from 100 MHz to 6 GHz. The calculated reflection loss of a single-layer electromagnetic wave absorber (EM absorber) designed by using permendur composites indicates less than -20 dB around the matching frequency of 1 GHz.