The synthesis and characterization of the hexagonal Z ferrite, Sr3Co2Fe24O41, from a sol-gel precursor

The Z ferrite Sr3Co2Fe24O41, produced from a stoichiometric aqueous inorganic sol-gel precursor, is reported and its magnetic hysteresis loop characterized for the first time. The precursor was an iron(III)hydroxide sol stabilised with NO3- counterions and doped with stoichiometric nitrate salts, which had a particle size similar to halide stabilised Ba3Co2Fe24O41 Z ferrite precursor sols investigated previously. When fired the amorphous gel formed a mixture of alpha -Fe2O3, BaM and CoFe2O4 from 600 degreesC, but these products then converted directly to the pure Z phase at 1200 degreesC, without first forming the Y ferrite (Ba2Co2Fe12O22) phase always observed prior to Z ferrite crystallization in Ba2Co2Fe24O41 systems. The resulting material was a very soft ferrite, with a very low coercivity of 5.6 kA m(-1) and a magnetisation of 48.5 emu g(-1) at an applied field of 5 T. (C) 2001 Elsevier Science Ltd. All rights reserved.