Effect of magnetic field treatment on the electromagnetic properties of polymer composite based on barium hexaferrite at microwave frequencies

Polymer composite materials are used in widely different areas of science and industry. It is possible to change electromagnetic properties of composite materials by external treatments. The present work focuses on the change of electromagnetic characteristics of barium polymer composite, which is exposed to the external magnetic field with different strength. Composite materials, containing 65 wt. % concentrations of barium hexaferrite (Z-type) powder with a linear size of less than 80 µm as fillers and epoxy resin as matrix were prepared. Reflection coefficients were measured by coaxial method at frequency range of 0.01 – 18 GHz. It was revealed that reflection coefficients of barium hexaferrite and epoxy resin composite are very sensitive to the values of external magnetic field. There is nonlinear dependence of the reflection coefficients on the values of external magnetic field. The optimum value of the strength of the external magnetic field was shown to be equal 4 mT. The Cramers-Kronig relations were used to recover the real parts of the permeability and correct the imaginary parts of the permeability.