Synthesis and Evaluation of Microstructural and Magnetic Properties of Cr³⁺ Substitution Barium Hexaferrite Nanoparticles (BaFe_10.5−x Al_1.5Cr _x O₁₉)

Abstract

Pure barium ferrite and BaFe_10.5−x Al_1.5Cr _x O₁₉ (x = 0, 0.5, 1.0, 1.5, 2.0) nanoparticles were synthesized by auto-combustion sol–gel method. The effect of substituting Fe³⁺ ions by Al³⁺ and Cr³⁺ ions on the structural, chemical composition, morphology and magnetic properties of BaFe₁₂O₁₉ and BaFe_10.5−x Al_1.5Cr _x O₁₉ hexaferrites have been investigated using X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and vibrating sample magnetometer (VSM), respectively. The results confirmed that the hexagonal phase has been formed in all of nanoparticles and the value of lattice parameter (c) decreased, while the value of lattice parameter (a) remained nearly constant with the increase in Cr³⁺ ions contents in comparison to pure barium ferrite. The crystallite size and mean particle size of the nanoparticles lie in the ranges 33–42 and 35–70 nm, respectively. The VSM measurements show that with substituting Al and Cr cations in the hexagonal structure of barium ferrite, the saturation magnetization (M _s ) and remanence magnetization (M _r ) of the nanoparticles reduce, while coercive field (H _c ) increased from 4.45 kOe for pure barium ferrite to 6.9 kOe for BaFe_10.5Al_1.5O₁₉ (x = 0) due to the increase in the magnetocrystalline anisotropy and the decrease of the particle size.