Design of Microwave Absorbing Coatings With New Ni and La Doped Hexaferrites

We conducted a theoretical and experimental study of the single-layer microwave absorbers employing ferrite composites. By combining zero-reflection solutions with the typical electromagnetic behavior of ferrites, we distinguish between matching mechanisms (resonance and geometrical type) which occur in bulk and composite specimens. Explicit design guidelines concerning the material properties are thereby indicated, contrary to empirical and erroneous design objectives. Additionally, the calculation of the thickness to λ/4 ratio is promoted to mitigate the common misconceptions about the reflection loss (RL) source. The simulated RL maps of new planar hexaferrite composites support our theoretical analysis. Furthermore, low rate La and Ni doping in SrCo₂ - W appears to yield increased RL (up to 45 and 65 dB) of wider bandwidth at lower frequency (6-18 GHz) and for smaller coating thicknesses.