Fast characterization of magnetic impurities in single-walled carbon nanotubes

We have demonstrated that the magnetic susceptibility measurement is a nondestructive, fast, and accurate method to determine the residual metal catalysts in a few microgram single-walled carbon nanotube (SWCNT) sample. We have studied magnetic impurities in raw and purified SWCNTs by magnetic susceptibility measurements, transmission electron microscopy, and thermogravimetry. The data suggest that the saturation magnetic moment and the effective field, which are caused by the interparticle interactions, decrease and increase, respectively, with the decrease of the particle size. Methods are suggested to overcome the uncertainty associated. (C) 2003 American Institute of Physics.