Optimized magnetic and dielectric properties of Co2Y ferrite for UHF antenna applications achieved via Cd2+ ion doping

Despite their exhibit high cut-off frequency and low sintering temperature, which make Y-type hexaferrites promising for high-frequency applications, their relatively low permeability and high loss have restricted their utility in antenna miniaturization. In this study, a series of Y-type hexaferrites Ba 2 Co 2- x Cd x Fe 12 O 22 ( x  = 0.0, 0.5, 1.0, 1.5) were synthesized, and the effects of Cd 2+ substitution on the phase structure, microstructure, magnetic properties, and high-frequency magneto-dielectric response were systematically investigated. X-ray diffraction (XRD) analysis confirmed the formation of a pure Y-type phase and detected significant lattice expansion. Scanning electron microscopy (SEM) revealed a plate-like grain morphology, with enhanced densification observed at higher Cd 2+ doping levels. Vibrating sample magnetometry (VSM) measurements demonstrated that the saturation magnetization ( M s ) remained essentially stable, whereas the coercivity ( H c ) decreased progressively, leading to a reduction in the magnetocrystalline anisotropy constant ( K 1 ). Consequently, the real parts of both complex permeability ( μ′ ) and permittivity ( ε′ ) exhibited marked improvement around 0.6 GHz ( μ′ from ∼2.2 to ∼4.5, ε′ from ∼4.5 to ∼6.2). Finally, an antenna simulated using the properties of the A3 sample ( x  = 1.0) achieved a compact size of 0.299 λ 0  × 0.256 λ 0  × 0.0149 λ 0 and an ultra-wide bandwidth of 42.9% (640-990 MHz) in the UHF band, demonstrating both miniaturization and excellent broadband performance.