Formation and magnetic properties of γ-Fe2O3particles surface modified with crystallized cobalt-ferrite
- 1 January 1980
- journal article
- Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Transactions on Magnetics
- Vol. 16 (1) , 17-19
- https://doi.org/10.1109/tmag.1980.1060540
Abstract
Acicular &-Fe2O3particles were heated at 90&C in alkali solution containing Co2+and Fe2+with Co2+/Fe2+ratio of 0.5. The coercivity of resultant particles increased linearly with increasing the Co2+content, and the coercivity of 900 Oe was obtained for the particles with Co2+content of 7 wt%. The shape of the particles is acicular, and an appreciable variation of morphology by the treatment in alkali solution was not observed. Cobalt-ferrite was expected to crystallize epitaxially on the surface of &-Fe2O3particles, and the increase of coercivity was attributed to the magnetic anisotropy of the cobalt-ferrite. A variation of coercivity by annealing at 60&C and print-through were small compared with those of the particles in which iron were homogeneously substituted by cobalt ions. Such stability was explained by considering that a very high concentration of cobalt ions exist only on the surface of &-Fe2O3particles, and the migration of cobalt ions is extremely difficult.Keywords
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