Carbon nanostructures with unusually large paramagnetic moments have been discovered in a theoretical study of the electronic and magnetic properties of carbon nanotubes bent into toroids. Specifically, nanotori formed from metallic nanotubes with ${\lambda }_F=3T$, where ${\lambda }_F$ is the Fermi wavelength and $T$ the translation vector of the nanotube, exhibit giant paramagnetic moments at selected radii (“magic radii”), while the ones with ${\lambda }_F=T$ are paramagnetic at any radius. The large paramagnetic moment is due to the interplay between the toroidal geometry and the ballistic motion of the $\pi$ electrons in the metallic nanotube.

• Received 30 October 2001

DOI:https://doi.org/10.1103/PhysRevLett.88.217206