Composition and magnetic studies of ultrafine Al-substituted Sr hexaferrite particles prepared by citrate sol-gel method

► Ultrafine SrFe12−xAlxO19 particles were prepared by sol-gel method. ► The gels were annealed at 950 °C for 2 and 24 h. ► Particle size and magnetic properties depend on Al substitution and annealing time. ► Hc and Ms are, respectively, 73-96% and 83-91% of the bulk values. ► The highest Hc value of 10.1 kOe was achieved for this sample series.