The character of ferromagnetic nanoparticle system depend to particle size and anisotropy effects

It was studied that relation of particle size, anisotropy,and temperature.A relation of coercivity (Hc),particle size (d),and temperature (T) was built by according to experimental results of Fe/SiO2,Fe/Al2O3 and Fe0.3Cu0.7 granular filem,and Néel-Bron theory and the Stoner-Wohlfarth model.It was found that the coercive force is granular films as a function of particle diameter (d).With increasing the particle size,Hc increases abruptly and attains maximum around dm (=18-20 nm),and then decreses as Hc∝1/d.