Particle size influence to the microwave properties of iron based magnetic particulate composites

Using the combination of Gilbert equation and an extended effective medium theory, high frequency intrinsic and effective permeability was calculated for Fe particles in a non-magnetic matrix (epoxy resin). It was found that the microwave properties (the relative complex magnetic permeability) of the composite were influenced by many material properties, such as saturation magnetization (4πMs), crystal anisotropy field (Ha) and electric resistivity (ρ). Experimental results also showed that particle size played an important role in the microwave performance. The effective magnetic permeability is strongly dependent on the particle size of magnetic spheres in the composite. Our theoretical calculation and experimental results have shown that fine Fe particles are promising for the application as microwave absorbers.