PREPARATION AND MAGNETIC-PROPERTIES OF ULTRAFINE SRFE12O19 PARTICLES DERIVED FROM A METAL CITRATE COMPLEX

Magnetoplumbite-type strontium ferrite (SrFe12O19) powders have been p repared from metal citrate complexes and their magnetic properties hav e been studied. The optimum pH condition (almost-equal-to 6.5) for the formation of metal citrate complexes was predicted through the theore tical consideration of thermodynamic equilibrium constants of the corr esponding metal salts in an aqueous solution. Nanometer-sized ferrite particles (almost-equal-to 50 nm) could be obtained through the therma l decomposition of polymeric citrate precursor at relatively low tempe rature (850-degrees-C). A large coercive force of 6500 Oe could be obt ained, which is one of the highest values reported so far for isotropi c SrFe12O19 samples and close to the theoretical limit.