Simultaneous substitution of Co2+and Zn2+ions in submicronic acicular γ - Fe2O3particles

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Abstract
In iron sesquioxide of acicular shaded &-Fe2O3simultaneous substitution of Co2+and Zn2+ions leads to the formation of mixed-defect ferrites and modulation of magnetic properties is of interest for their application to high density magnetic recording. It is shown that the coercive force, remanent magnetization and saturation-magnetization are controlled by a judicious choice of the contents of Co2+and Zn2+, while it is indispensable to optimize the morphological features like the average size of the crystallites, the shape, the size and texture of the particles. A high value of coercive force (650-700 Oe) and of the remanent magnetization (35-45 emu/g) had been obtained with a minimal content of cobalt ions (Co2+= 2.5 to 3% by wt.) permitting limits to the magnetocrystalline anisotropy of these compounds and their thermal variation near the ambient temperature. The influence of the zinc content had been systematically studied notably in relation to its effect on the structural, morphological and magnetic properties of the ferrites.