Synthesis and electromagnetic properties of U-type hexaferrites Ba ₄B ₂Fe ₃₆O ₆₀ (B: Co, Ni, Cu)

Polycrystalline samples of U-type hexaferrites Ba ₄B ₂Fe ₃₆O ₆₀ (B: Co, Ni and Cu) were synthesized using a modified solid state reaction technique. The sintered hexaferrites were tested for their crystalline quality using x-ray diffraction technique and their magnetic properties using the Physical Property Measurement System (PPMS). The individual ferrites were further used as fillers to prepare composites using a polyethylene matrix. The composites were tested for their complex permittivity and permeability spectra and finally reflection loss spectra were derived from these results. Among the studied composites, lowest and highest values of saturation magnetization were 25 and 35 emu/g, respectively, for the Cu doped hexaferrites and the Co doped hexaferrites. All the studied composites demonstrated microwave absorption property, which was tunable by manipulating the sample thickness. Co-doped composites offered the highest absorption (∼98%) and were found the most suitable to suppress electromagnetic interference.