Influence of citric acid content on magnetic properties of BaFe12O19 powder prepared by sol-gel auto-combustion method

BaFe12O19 powders with nanocrystalline sizes were produced by sol-gel auto-combustion method. The precursors were prepared under the molar ratios of citric acid to the metal nitrate of 0.5, 1.0 and 1.5. Appropriate ethylene diamine (C2H8N2) was added in order to adjust pH of 7. The ions distribution of citric acid at different pH explains the effect of citric acid in the starting solution. The XRD patterns of the as-burnt powders and annealing powders show different phases for different citric acid content. In addition, the lattice constants (a, c) derived from X-ray diffraction pattern were changed from 0.58881 nm to 0.58997 nm and 2.32057 nm to 2.32296 nm respectively. The data from VSM indicated that the powder with high citric acid content took on good magnetic properties. Pure single BaFe12O19 of the specific maximum magnetization M(1 T) ≈ 49.73 Am2/kg, the specific remanent magnetization M r ≈ 30.77 Am2/kg and the coercive force H c ≈ 467 kA/m was produced when the molar ratios of citric acid to the metal nitrate was 1.5.