Facile sonochemical preparation and magnetic properties of strontium hexaferrite (SrFe12O19) nanoparticles

The hard magnetic material M-type strontium hexaferrite (SrFe12O19) was prepared by a facile surfactant-free sonochemical strategy and subsequently by a calcination process. The surface morphologies, structures, and Curie temperature of the obtained final product was investigated by powder X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), BET (Brunauer–Emmett–Teller) specific surface area (SSA) and thermogravimetric analysis (TGA). XRD confirmed the formation of single-phase strontium hexaferrite with space group P63/mmc (194) and hexagonal structure and the mean primary crystallite size was found to be 44 nm. The morphology of synthesized SrFe12O19 product was in spherical shape with good crystalline nature. The measured Curie temperature (Tc) of the nanoparticles was around 462 °C. The magnetic property of the sample was measured by using a Superconducting Quantum Interference Device (SQUID) magnetometer at temperatures between 4 and 300 K. The measured saturation magnetization (Ms) at 300 K, 33 emu/g, is significantly lower than that found for bulk SrFe12O19, probably reflecting a size effect of the nano-particles.