Dipolar chains formed by chemically synthesized cobalt nanocubes

Cobalt nanocubes with an average edge length of 50 nm and epsilon crystalline structure were synthesized via thermo-decomposition in 1,2-dichlorobenzene at 120 deg. C in the presence of surfactants. These nanocubes form dipolar chains upon drying in zero applied field and bundles of chains along the direction of an applied magnetic field. The magnetic measurements reveal strong interparticle couplings among the nanocubes in their dried magnetic-field-induced assemblies. The constricted hysteresis loops and near-zero coercivity indicate the existence of vortex states in the assemblies. Exposure to electron beam heats up the nanocubes and turns the dipolar chains into nanowires.