Experimental and theoretical investigation of SrFe12O19 nanopowder for permanent magnet application

Strontium M-type hexagonal ferrites were synthesized at different calcination temperatures (800 degrees C, 1000 degrees C and 1100 degrees C) using sol-gel autocombustion method. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Mossbauer spectroscopy (MS) and superconducting quantum interference device magnetometer (SQUID) techniques were used to characterize crystal structure, phase composition, morphology and magnetic properties. TGA gives T = 800 degrees C as beginning of suitable calcination. Hexaferrite structure of single phase is obtained according to XRD results for all samples with crystallite size between 28 nm and 35 nm. SEM images show the growth of grain size with increasing of annealing temperature. (BH)(max) is calculated based on SQUID results and shows an enhancement between T = 800 degrees C and T = 1000 degrees C of 25%. The magnetic properties observed at low temperature are explained and confirmed by ab-initio calculations.