Evaluation of composite electromagnetic wave absorber made of polystyrene resin and permalloy or sendust

The frequency dependences of the complex permeability mu(r)*, complex permittivity epsilon(r)*, and return loss were investigated for composite electromagnetic wave absorbers made of soft magnetic materials (permalloy or sendust) and polystyrene resin. For permalloy, two types of particle shape were used: grain-type or flake-type. The volume mixture ratio of magnetic materials was varied in the range from 40 % to 70 %. The values of the real part mu' and imaginary part mu" of mu(r)* increased with increasing mixture ratio of magnetic materials. The frequency dependence of mu(r)* for flake-type permalloy composite was similar to that for sendust composite. All absorbers showed the absorption of electromagnetic waves in the frequency range above 1 GHz.