Study of microwave absorptions in M-hexaferrites for anti-radar applications

Microwave absorption of sintered M-type hexaferrites (BaFe12-2xRuxZnxO19) is investigated as a function of the substitution ratio x. The substitution with Ru and Zn has been shown to reduce the,axial anisotropy of the BaM-hexaferrite which becomes in-plane for x approximate to 0.4. Large saturation magnetization and in-plane magnetic anisotropy allow to obtain high permeability values at microwave frequencies. To study the behavior of the ferrites at these frequencies, the complex constitutive parameters epsilon and mu (respectively permittivity and permeability) are simultaneously measured from 0.5 up to 18 GHz using a coaxial technique. Two absorption phenomena are observed: the ferrimagnetic resonance and the domain wall relaxation, the latter is studied with the Globus' model. Anti-radar applications are also mentioned.