Microwave refraction coefficient of composite with flakes of Fe-Si -Nb-Cu-B alloy

The microwave refraction coefficient of a composite consisting of flakes of Fe-Si-Nb-Cu-B alloy placed into epoxy resin matrix has been studied. Magnetic field dependences of the transmission and reflection coefficients have been measured in the frequency range from 12 to 38 GHz. The minima of the transmission and reflection coefficients caused by ferromagnetic resonance and the maximum of the reflection coefficient caused by ferromagnetic antiresonance have been observed. From the frequency dependences of the transmission and reflection coefficients and from the linewidth of ferromagnetic resonance, the permittivity and permeability have been estimated, which has allowed one to assess the wavenumber and complex refraction coefficient. It has been shown that the material under consideration behaves as a dielectric at DC and as a lossy dielectric at microwave frequencies in the absence of magnetic field. Near the field of ferromagnetic resonance, the real and imaginary parts of complex refraction coefficient are of the same order as in a conductive medium.