Studies on Exchange-Coupled Magnetodielectric Ceramics for Microwave Absorption in Ku-Band

Abstract

Series of exchange-coupled BaFe12O19 (BaM)/CoFe2O4 (CFO) and BaM/Co0.5Zn0.5Fe2O4 (CZFO) composites were synthesized using the autocombustion method. Effect of soft (CFO/CZFO) phase weight fraction on structural, magnetic, and microwave properties of composites has been investigated and compared. X-ray diffraction patterns and scanning electron microscope (SEM) micrographs confirmed the presence of BaM and CFO/CZFO phases with well-distinguished grains in the composites. Existence of interfacial coupling was verified by smooth demagnetization behavior and single peak in corresponding $\text{d}M/\text{d}H$ curves. Saturation magnetization ( $M_{s}$ ) and coercivity showed strong dependence on exchange interactions between hard and soft magnetic spins. Compared to BaM, $M_{s}$ of composites were 22% and 36% higher with CFO and CZFO, respectively. Frequency-dependent complex permittivity ( $\varepsilon$ ) and permeability ( $\mu $ ) in ${\text{K}}_{u}$ -band were found to be dependent upon the relative composition and nature of soft phase. Maximum $\varepsilon $ of 45 and $\mu $ of 1.6 were achieved for BaM/CFO (50/50) composite. Exchange-coupled magnetodielectric with high $\varepsilon $ and $\mu $ were developed for various microwave applications.