科研之友
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摘要
We report the phenomenon of size segregation and the experimental evidence for the presence of correlated areas mediated by dipolar interactions in three-dimensional Fe nanoparticle assemblies. Iron nanoparticles dispersed in ethanol assemble into tabular whiskers (8 mu m x 40 mu m in cross section with lengths up to 10 cm) due to dipolar interactions. Magnetic force microscopy observations on iron nanoparticle compact assemblies prove the local magnetic correlation of the Fe nanoparticles due to dipolar coupling and the formation of domain-like structures in expanded dimensions. Magnetic measurements show that the coercivity and the low field magnetic susceptibility of the Fe nanoparticle assemblies increase while the saturation magnetization decreases with the increasing inter-particle distance.
