Colloque C1, SupplCment au Journal de Physique I11 de mars 1997 Microwave Electromagnetic Characteristics of New Substituted

Abstract. The substitution of x(Ti-Co) for 2x Fe cations reduces the strong axial anisotropy of the BaM-hexaferrite, which becomes in-plane for x = 1.3. Then M(Ti-Co) substituted hexaferrite have been extensively investigated as promising material for magnetic recording or hyperfrequency wave absorption. But saturation magnetization and ordering temperature are unfortunately reduced in proportion to the substitution ratio. Doping barium hexafemte with A-Me elements (A = Ru, Ir; Me = Co, Zn) produces the same effects for a much smaller substitution ratio. Ordering temperature and saturation magnetization are consequently much higher. Large saturation magnetization associated with in-plane magnetic anisonopy allows to obtain high magnetic permeability values on a wide frequency range at high values of some GHz. Complex electromagnetic characteristics: k',)I", E ' and E " of these new M(A-Me) substituted hexaferrites have been simustaneously measured at high frequency (0.5 to 18 GHz) using coaxial wire device on ceramic samples. The ferromagnetic resonance observed in these ceramics strongly depends on both their magnetic and microstrucutral properties. Results are discussed in tenns of substitution ratio and microstructure depending on preparation conditions. 1