Ba-M+Y (Ba_4−XCo_2+XFe₃₆O₆₀) complex hexaferrite: structural, electrical, magnetic, and enhanced microwave absorbing properties over 8–18 GHz frequency

Hexaferrites are a class of materials that have practical applications as microwave absorbing materials (MAMs) and radar absorbing materials (RAMs). Herein, complex (Ba_4−XCo_2+XFe₃₆O₆₀) (0 ≤ X ≤ 1), i.e., Ba-M+Y, stacked, hexagonal crystal-structured, cobalt-substituted barium hexaferrite was synthesized using a facile coprecipitation method. The Ba-M+Y hexaferrite was constructed from a mixture of M-type (BaFe₁₂O₁₉) and Y-type (Ba₂Co₂Fe₁₂O₂₂) phases. The M phase is difficult to magnetize, whereas the Y phase is soft. Therefore, in this type of hexaferrite, thick films were magnetized at relatively lower magnetic fields with lower coercivity values. For the synthesis, a lower temperature was preferred to achieve a crystal structure with the mixed M+Y phase. X-ray diffraction patterns showed the formation of the M+Y mixed-phased stacked complex hexagonal crystal structure. The crystallite size, estimated using the Scherrer equation, was found to be 26–64 nm. The surface morphology showed a hexagonal plate-like structure and stacking. The microwave absorbing properties were investigated over the frequency range of 8–18 GHz using the X and Ku bands. The 60%-cobalt-substituted sample (X = 0.6) showed a maximum absorption of 94%, whereas the lowest reflection is ~ 1%. The hysteresis loop showed that saturation magnetization varies with the cobalt content. This ferrite is a potential candidate for application in MAMs and RAMs.