We have studied the magnetic properties of bcc-Fe fine particles with a diameter D of 3/spl sim/40 nm prepared by a vapor condensation process. The particles exhibit uniaxial anisotropy of 2.0/spl sim/3.0/spl times/10/sup 6/ erg/cc which is much larger than that of bulk Fe (0.5/spl times/10/sup 6/ erg/cc). Numerical calculations taking into account dipolar interaction and thermal agitation reproduce the particle size dependence of coercivity very well. According to the present work, magnetization reversal of Fe particles proceeds via coherent rotation for D15/spl sim/20 nm. It is, however, still uncertain why the magnetic anisotropy of Fe fine particles is uniaxial and so large.
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Ibusuki et al. (2001) studied this question.
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