The magnetic properties of vapor deposited Fe and Co particles in the size range of 50-350 AA are studied. Magnetization, Mossbauer and structural data show a core-shell morphology, where the core is metallic and the shell is a polycrystalline Fe (Co)-oxide. A sharp reduction in magnetization is observed in particles with a size below 100 AA. This is attributed to surface/interface spin canting brought about by the ferrite oxide shell. The effect of various surface chemistries on the hysteretic behavior is systematically studied. The results clearly indicate that the oxide shell controls both the magnitude and the temperature dependence of coercivity.
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