Abstract
An original method for obtaining a composite made up of cobalt-iron alloy and cobalt doped magnetite is described. This method is based on a disproportionation reaction in a liquid medium at 110°C. Chemical analysis and crystallographic measurements allow a schematic chemical formula for the composite (Fe 0.2Co 0.8) 0.8[Fe 2.38Co 0.62O 4] to be given. The crystallographic parameter of the cobalt doped magnetite of spinel structure is a = 8.396(1) Å. Cobalt-iron alloy presents BCC and FCC structures and does not oxidize up to 320°C. At room temperature this composite is characterized by a saturation magnetization of 90 emu/g and a coercive field of 1700 Oe. A further heating at 200°C increases the concentration of metallic phase of the BCC structure and the saturation magnetization, decreases the crystallographic parameter of spinel phase and the coercive field. Above 320°C, the alloy oxidizes; the spinel CoFe 2O 4 crystallizes at 900°C.
Published Version
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