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 ≈ 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 ε and μ (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.