Microwave loss power in composite magnetic fluids
Pages 51-55
P. C. Fannin, C. N. Marin, I. Malaescu, N. Stefu
Abstract.
Frequency (f) and biasing field (H) dependence of the complex magnetic permeability µ(f, H) = µ'(f, H) - i µ"(f, H), and of the complex permittivity ε(f, H) = ε'(f, H) - i ε"(f, H), of three kerosene based magnetic fluid samples, over the range 200 MHz to 3 GHz and 0 to 35 kA/m, respectively, were analyzed. Sample MF1 contained Ni0.4Zn0.6Fe2O4 particles, sample MF2 contained Mn0.6Fe0.4Fe2O4 particles and sample MF3 was obtained by mixing MF1 and MF2 in a 1:1 proportion. Based on the complex magnetic permeability and complex dielectric permittivity measurements of each sample for different field values, the total specific loss power (due to magnetic and dielectric losses) was computed. Theoretical specific loss power of the composite sample MF3 was also computed. The computation was based on the superposition principle in the approximation of no inter-particle interactions. The experimental values of the specific loss power were compared to the theoretical ones.
In zero biasing field, the measured specific loss power was found to be in good agreement with the theoretical values. With the increase of the biasing field, deviations of the experimental values from the theoretical results were observed. These differences are due to the biasing field induced particle agglomerations.
The paper proves the potential usefulness of the mixing technique in the design of microwave electromagnetic absorbers.