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

¹ LDIM EA 253/DSPT4/MENRT, Paris VI, 4 place Jussieu, 75252 Paris Cedex 05, France
² LMGP (URA 1109 du CNRS), ENS de Physique de Grenoble, 38402 St Martin-d'Hères Cedex, France

Corresponding author: dubrunf@ccr.jussieu.fr

Received: 14 April 1998
Revised: 21 September 1999
Accepted: 21 September 1999
Published online: 15 September 1999

Abstract

Microwave absorption of sintered M-type hexaferrites (BaFe_12−2xRu_xZn_xO₁₉) 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.