Microwave attenuation properties of W-type barium ferrite BaZn2-xCoxFe16O27 composites

The complex permeability and permittivity, the relationship between dynamic and static properties, and attenuation properties have been studied for BaZn2-xCoxFe16O27 composites with x=0.7-2.0. The results show that the resonance frequency f(R) is controlled by the out-of-plane anisotropy field H-theta, and the static permeability mu(0)(') is related to the in-plane anisotropy field H-phi. For appropriate resonance frequency and high complex permeability, the percentage bandwidths of DeltaW=Deltaf/f(0)>90% for attenuation of 10 dB or more can be achieved by composites with x=0.7 and 1.0. Therefore, W-type barium ferrites with easy c-plane anisotropy are good candidates for electromagnetic materials with low reflectivity over broad frequency range at microwaves. (C) 2004 American Institute of Physics.