$^{13}$C NMR Study of Single-Walled Carbon Nanotubes

We have performed $^{13}$C nuclear magnetic resonance (NMR) measurements on single-walled carbon nanotubes. Spectrum, shift,linewidth, and $T_1$ have been measured as a function of temperature from 4 K to 200 K under the magnetic field of 4.7 T. Spectrum shows a narrow lineshape for the $^{13}$C nucleus. Shift is very small and shows no significant change in the whole temperature range. The linewidth becomes broader with decreasing temperature from 13 kHz at 200 K to 21 kHz at 4.6 K. The spin-lattice relaxation recovery is found to exhibit three types of relaxation channels; the fastest rate comes from magnetic impurities on the surface and the other two are due to metallic and non metallic parts of the nanotubes.