The formation of legume-like structures of Co nanoparticles through a polymer-assisted magnetic-field-induced assembly

A unique one-dimensional (1D) legume-like structure of cobalt nanoparticles was prepared by a simple magnetic-field-induced assembly approach with the assistance of polyvinylpyrrolidone (PVP). In each 'legume', cobalt nanoparticles were regularly aligned along the lines of magnetic force in a row with visible spacing between adjacent nanoparticles and permanently linked with PVP molecule layers in order to maintain the ordered shape after the removal of the external magnetic field. Magnetic measurement showed that these legume-like structures were superparamagnetic at room temperature, while appearing somewhat ferromagnetic at 10 K, obviously indicating magnetostatic coupling between nanoparticles at low temperature. This novel legume-like structure would provide a new model system for the study of magnetization properties of one-dimensionally ordered magnetic nanostructures.