Structure and magnetic properties of Fe/SiO2 and Fe/Al2O3 granular films were studied in the particle size (d) range of 1–50 nm. The coercivity (Hc) shows a maximum around 600 Oe at the particle size dm≈18 nm, and then decreases in the larger particle size range for both Fe/SiO2 and Fe/Al2O3 systems at room temperature. A relation of coercivity, particle size, and temperature was built by using the Néel–Brown theory and the Stoner–Wohlfarth model basically. The experimental results were successfully fitted by assuming that the α-Fe particles possess uniaxial surface anisotropy Ks≈0.4 erg/cm2.
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Chen et al. (1998) studied this question.
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