One-Dimensional Assemblies of Silica-Coated Cobalt Nanoparticles: Magnetic Pearl Necklaces

Verónica Salgueiriño-Maceira, Miguel A. Correa-Duarte, Alfred Huchtd, and Michael Farle
J. Magn. Magn. Mater., 2006, 303, 163–166


Silica-coated cobalt nanoparticles were found to organize into chains when driven by a weak external magnetic field. Strong dipole–dipole magnetic interactions are believed to be the driving force of the self-organization once the cobalt nanoparticles undergo the superparamagnetic to ferromagnetic (SP–FM) transition, as increasing their size during the synthesis process. The method, although simple, produces structures resembling pearl necklace-like structures, comparable to one-dimensional species obtained in more laborious processes. Molecular dynamic simulations taking magnetic dipolar forces into account reproduce the observed self-assembled structures. The nanoscale engineering of this type of colloids is expected to extend the spectrum of magnetic effects and functionalities.