Structural and magnetic properties of SrFe12O19 hexaferrite synthesized by a modified chemical co-precipitation method

M-type strontium hexaferrite (SrFe₁₂O₁₉) particles had been prepared by a modified chemical co-precipitation route. Structural and magnetic properties were systematically investigated. Rietveld refinement of X-ray powder diffraction results showed that the sample was single-phase with the space group of P6₃/mmc and cell parameter values of a=5.8751 Å and c=23.0395 Å. The results of field-emission scanning electronic microscopy showed that the grains were regular hexagonal platelets with sizes from 2 to 4 μm. The composition determined by energy dispersive spectroscopy is the stoichiometry of SrFe₁₂O₁₉. The ferrimagnetic to paramagnetic transition was sharp with Curie temperature T_C=737 K, which further confirmed that the samples were single phase. However, it was found that the coercivity, saturation magnetization and the squareness ratio of the synthesized SrFe₁₂O₁₉ samples were lower than the theoretical values, which could be explained by the multi-domain structure and the increase of the demagnetizing factor.