Enhancement of coercivity in Co modified /spl gamma/-Fe/sub 2/O/sub 3/ particles by adsorption of ions

Several ions were adsorbed on the surface of acicular Co modified /spl gamma/-Fe/sub 2/O/sub 3/ particles by a surface treatment in their wash process. Coercivity of prepared particles was increased from 580 to 640 Oe and saturated magnetization was decreased from 78.7 to 77.5 emu/g with the amount of adsorbed ion after the treatment with calcium, magnesium and silicon. On the other hand, aluminum,a trivalent ion did not lead to an enhancement in coercivity with the same treatment. Dependence on ionic valence was observed in this H/sub c/ behavior. Several ideas were discussed to explain the He enhancement, and possible enhancement mechanisms for this behavior have been evaluated.<
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