Effect of carbon and sintering temperature on the structural and magnetic properties of SrFe₁₂O₁₉ nanoparticles

SrFe₁₂O₁₉ magnetic nanoparticles with hexagonal magnetoplumbite structure were synthesized by a modified polyacrylamide gel route and characterized by X-ray diffraction, scanning electron microscope, Fourier transform infrared spectrophotometer, and vibrating sample magnetometer. To obtain large squareness ratio of SrFe₁₂O₁₉, a certain amount of carbon particles were introduced to the precursor solution. X-ray diffraction patterns showed that the carbon and sintering temperature accelerated hexagonal SrFe₁₂O₁₉ phase formation and not changed the hexagonal magnetoplumbite structure. The phase transformation process is closely correlated not only to the sintering temperature but also to the addition carbon particles. In the Fourier transform infrared spectra of SrFe₁₂O₁₉ sample, three obvious absorption peaks at 600, 550 and 439 cm⁻¹ were observed. The carbon introducing to SrFe₁₂O₁₉ precursor solution improved the surface morphology and enhanced the squareness ratio value. The coercivity and squareness ratio of the hexagonal SrFe₁₂O₁₉ are closely correlated not only to the crystallite size but also to the dispersion of nanoparticles of SrFe₁₂O₁₉ sample.