In this work, the sol-gel auto-combustion method has been successfully used to prepare nanocrystalline stron- tium hexaferrite doped with cobalt at iron sites (SrFe12 − x CoxO19, x = 0–1). The crystal structure, morphology, and magnetic properties of samples were systematically investi- gated using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM), respec- tively. The three vibrational modes were observed in the FT-IR spectra of calcined samples, which indicated the pres- ence of metal-oxygen stretching bands in hexaferrite struc- ture after calcination treatment. The XRD results confirmed the single-phase M-type hexagonal structure for SrFe12 − x CoxO19 samples with x ≤ 0.5; however, for the samples with x > 0.5, the cubic CoFe2O4 phase was also appeared. The average particle size etermined by TEM analysis was found to be about 87 nm (for x = 0) and 110 nm (for x = 1) whereas the cobalt ubstitution leads to the larger particles. The saturation magnetization increased with cobalt content up to x = 0.5 and then decreased slowly on further increaseof the dopant concentration, while the coercivity ecreased continuously with increasing Co content.

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