Microwave absorption in Sc- and CoTi-substituted Ba hexaferrite powders

Investigations of hexagonal ferrites as a gyromagnetic medium allow the analysis of phenomena related to ferromagnetic resonance (FMR) in ferrites with high internal anisotropy. In the present work, (Sc)- and (CoTi)-substituted M-type hexaferrite powders are examined on the basis of the general formula BaM_xFe_12-xO ₁₀, where M=(Sc) and (CoTi), while x=0-1.8. Some relationships are established concerning the influence of the particle size, orientation, and chemical composition on microwave absorption in a wide frequency range (5-70 GHz). It is concluded that replacing some of the Fe³⁺ ions in a Ba hexaferrite with (Sc) and (CoTi) opens up the possibility of controlling the microwave operating frequency of these materials by varying the degree of substitution. The results obtained suggest the predominant influence of the size and geometry of highly anisotropic gyromagnetic particles on the degree of microwave absorption in the region of natural FMR