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

Microwave absorption of sintered M-type hexaferrites (BaFe12-2xRuxZnxO19) i s 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-hex aferrite which becomes in-plane for x approximate to 0.4. Large saturation magnetization and in-plane magnetic anisotropy allow to obtain high permeab ility values at microwave frequencies. To study the behavior of the ferrite s at these frequencies, the complex constitutive parameters epsilon and mu (respectively permittivity and permeability) are simultaneously measured fr om 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.