Magnetism in Fe-based and carbon nanostructures:: Theory and applications

We demonstrate that it is possible to encapsulate ferromagnetic nanowires of Fe, FeCo and FeNi inside carbon nanotubes via chemical vapor deposition methods. These wires exhibit extremely high coercive fields when compared with the bulk phases. We review the state-of-the an characterization carried out on these novel wires and discuss the importance of having aligned arrays of carbon nanotubes filled with ferromagnetic materials, towards the development of novel magnetic storage devices. In this context, we will show from the experimental and theoretical stand points, that the wire shape, aspect ratio and inter-wire distances play a crucial role in the fabrication of novel storage components. In addition, we theoretically show that pure carbon nanostructures such its carbon nanotori, perforated fullerenes and nanoporous graphitic structures, exhibiting negative Gaussian curvature introduced by the presence of non-hexagonal rings, behave as strong paramagnets experiencing large magnetic moments when an external magnetic field is applied. The latter results Could explain some of the magnetic properties observed experimentally in carbon nanofoams and polymerized C-60 phases. We envisage that magnetism in different families of nanostructures will be playing a key role in the development of emerging technologies in the present Century. (c) 2006 Elsevier SAS. All rights reserved.