Damping of electromagnetic waves by small spheres suspended in an insulator

The intentional degradation of electromagnetic waves by their penetration into a medium composed of somewhat sparsely distributed energy-absorbing ferrite spheres suspended in an electrical insulator is investigated. The influence of wave frequency, sphere size, resistivity, and complex permeability on wave stopping power by such a composite is investigated analytically and related in equation form. Eddy currents are induced in the spheres by the applied magnetic field of the wave are dissipated by friction. Magnetic hysteresis phenomena cause additional losses. This results from the continual distortion of the crystalline structure of the Weiss domains and spin reorientation of the bound electrons induced by the waves. In general, the hysteresis phenomenon has a much greater sensitivity to the independent parameters than do eddy currents over the range of variables studied here.<>