Enhancement of microwave absorption of nanocomposite BaFe₁₂O₁₉/α-Fe microfibers

Nanocomposite BaFe₁₂O₁₉/α-Fe microfibers with diameters of about 1-5 μm are prepared by the organic gel-thermal selective reduction process. The binary phase of BaFe₁₂O₁₉ and α-Fe is formed after reduction of the precursor BaFe₁₂O₁₉/α-Fe₂O₃microfibers at 350 ℃ for 1 h. These nanocomposite microfibers are fabricated from α-Fe (16-22 nm in diameter) and BaFe₁₂O₁₉ particles (36-42 nm in diameter) and basically exhibit a single-phase-like magnetization behaviour, with a high saturation magnetization and coercive force arising from the exchange-coupling interactions of soft α-Fe and hard BaFe₁₂O₁₉. The microwave absorption characteristics in a 2-18 GHz frequency range of the nanocomposite BaFe₁₂O₁₉/α-Fe microfibers are mainly influenced by their mass ratio of α-Fe/BaFe₁₂O₁₉ and specimen thickness. It is found that the nanocomposite BaFe₁₂O₁₉/α-Fe microfibers with a mass ratio of 1:6 and specimen thickness of 2.5 mm show an optimal reflection loss (RL) of -29.7 dB at 13.5 GHz and the bandwidth with RL exceeding -10 dB covers the whole Ku-band (12.4-18.0 GHz). This enhancement of microwave absorption can be attributed to the heterotructure of soft, nano, conducting α-Fe particles embedded in hard, nano, semiconducting barium ferrite, which improves the dipolar polarization, interfacial polarization, exchange-coupling interaction, and anisotropic energy in the nanocomposite BaFe₁₂O₁₉/α-Fe microfibers.