Investigation of Co nanoparticle assemblies induced by magnetic field

Cobalt nanoparticles were synthesized by using cobalt (II) acetate as precursor in an organic solution. Under the influence of a 0.05 T magnetic field, in a colloidal solution, the cobalt nanoparticles covered with surfactants were assembled into highly constrained linear chains along the direction of the magnetic field. After removal of the field the chains become floppy and then aggregate into “pearl necklaces” coiled structures upon gentle agitation. The differences of the magnetic properties between the magnetic field induced and random cobalt nanoparticles can be characterized by superconducting quantum interference devise (SQUID).