One-step solution fabrication of magnetic chains consisting of jingle-bell-shaped cobalt mesospheres

Using a one-step solution phase approach, the authors have synthesized uniform jingle bell-shaped cobalt mesopheres (550-750 nm) and assembled the mesospheres into long magnetic chains (20-30 μm). All of the cobalt spheres are hollow with ∼40 nm thick shells but each contains an ∼200 nm diameter solid ball. The nano- to mesoscale structures were realized via reaction of CoCl₂·6H₂O and N₂H ₄·H₂O in the presence of polyvinylpyrrolidone (PVP) in an ethylene glycol solution. Magnetic measurements show a coercivity of about 75 Oe with a remnance of 9.6 emu/g at 300 K. We propose a possible mechanism for the formation of the nanoto mesoscale structures.