Evolution of Magnetic and Structural Properties during Iron Plating of Carbon Nanotubes

Iron nanoparticles have been electrochemically deposited onto carbon nanotube (CNT) films. The CNT films were prepared by electrophoretic deposition using CNTs that were functionalized using a novel ozone-based process. Chemical characterization of the iron films was undertaken as a function of deposition time and related to their magnetic properties. In the initial stage of film growth, 20 nm cubic iron-rich crystals nucleate on individual CNTs. As the film grows, the iron crystals coalesce into a more continuous film and the elemental iron concentrations increase above 70 atomic percent. Changes in the chemical composition of the films during growth are reflected in the ferromagnetic properties, which show much higher coercivity values for thicker films relative to bulk iron. The film coercivity is related to the nanosized-cubic iron particles which form on the CNTs and is significantly enhanced when compared to that of iron films that form on planar graphite substrates, where the cubic crystal structure is not observed.