The synthesis and characterization of the hexagonal Z ferrite, Sr 3Co 2Fe 24O 41, from a sol-gel precursor

Abstract

The Z ferrite Sr 3Co 2Fe 24O 41, 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 NO 3 - counterions and doped with stoichiometric nitrate salts, which had a particle size similar to halide stabilised Ba 3Co 2Fe 24O 41 Z ferrite precursor sols investigated previously. When fired the amorphous gel formed a mixture of α-Fe 2O 3, BaM and CoFe 2O 4 from 600°C, but these products then converted directly to the pure Z phase at 1200°C, without first forming the Y ferrite (Ba 2Co 2Fe 12O 22) phase always observed prior to Z ferrite crystallization in Ba 3Co 2Fe 24O 41 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.