Preparation and magnetic properties of SrFe12O19/SiO2 nanocomposites with core–shell structure

SrFe12O19/SiO2 nanocomposites with a core–shell structure have been obtained. The core SrFe12O19 nanoparticles were synthesized by a citrate precursor technique with Fe/Sr ratios of 10.8, and silica was coated on SrFe12O19 forming complete coverage by the controlled hydrolysis and condensation of tetraethyl orthosilicate (TEOS). The composition, morphology and structure of the products were characterized by EDS, XRD, TEM, and IR spectroscopy, respectively. The results indicate that the product has a core–shell structure, which is combined through the chemical bond of Fe–O–Si. The magnetic measurements were carried out on a vibrating sample magnetometer (VSM), and the measurement results indicate the reduction of the magnetization of the SiO2 coated strontium ferrite nanoparticles compared with the uncoated ferrite nanoparticles. High coercivity also shows that the prepared uncoated and coated ferrite nanoparticles are not superparamagnetic.