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

Series of exchange-coupled BaFe
₁₂
O
₁₉
(BaM)/CoFe
₂
O
₄
(CFO) and BaM/Co
_0.5
Zn
_0.5
Fe
₂
O
₄
(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 dM/dH curves. Saturation magnetization (Ms) and coercivity showed strong dependence on exchange interactions between hard and soft magnetic spins. Compared to BaM, Ms of composites were 22% and 36% higher with CFO and CZFO, respectively. Frequency-dependent complex permittivity (ε) and permeability (μ) in Ku-band were found to be dependent upon the relative composition and nature of soft phase. Maximum ε of 45 and μ of 1.6 were achieved for BaM/CFO (50/50) composite. Exchange-coupled magnetodielectric with high ε and μ were developed for various microwave applications.