Hard magnetic SrFe12O19 (SrM) nanoparticles were synthesized by a facile sonochemical reaction. The magnetic nanoparticles were then added to acrylonitrile-butadiene-styrene, polystyrene, polycarbonate, and poly sulfone to make magnetic nanocomposites. The magnetic properties of the samples were also investigated using an alternating gradient force magnetometer. The strontium ferrite nanoparticles exhibited ferrimagnetic behaviour at room temperature, with a saturation magnetization of 39 emu/g and a coercivity of 5070 Oe. The distribution of the SrFe12O19 nanoparticles into the polymeric matrixes increases the coercivity
