Synthesis of strontium ferrite ultrafine particles using microemulsion processing

The strontium ferrite ultrafine particles have been prepared using the microemulsion processing. The mixed hydroxide precursor was obtained via the coprecipitation of Sr2+ and Fe3+ in a water-in-oil microemulsion of water/CTAB/n-butanol/isooctane. According to the investigation on the thermochemical properties by TGA/DTA and the phase analysis by XRD, it was shown that the precursor could yield pure strontium ferrite after calcination at 700 degreesC for 5 h while using an appropriate molar ratio of Sr/Fe in microemulsions. From TEM measurement, the diameters of the precursor and calcined particles were 3.8 +/- 0.7 and 50-100 nm, respectively. The magnetic properties characterized by a SQUID magnetometer showed that the saturation magnetization, remanent magnetization, coercivity, and squareness ratio were 55 emu/g, 28 emu/g, 492 Oe, and 0.51, respectively. The magnetization was also observed to increase with the decrease of temperature at 5-400 K. Compared with those reported earlier, the quite low coercivity implies the potential application of final product in the high-density perpendicular recording media. (C) 2001 Academic Press.