13C NMR Spectroscopy of KxC60: Phase Separation, Molecular Dynamics, and Metallic Properties

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Science  23 Aug 1991:
Vol. 253, Issue 5022, pp. 884-886
DOI: 10.1126/science.253.5022.884


The results of 13C nuclear magnetic resonance (NMR) measurements on alkali fullerides KxC60 are reported. The NMR spectra demonstrate that material with 0 < x < 3 is in fact a two-phase system at equilibrium, with x = 0 and x = 3. NMR lineshapes indicate that C3–60 ions rotate rapidly in the K3C60 phase at 300 K, while C660 ions in the insulating K6C60 phase are static on the time scale of the lineshape measurement. The temperature dependence of the 13C spin-lattice relaxation rate in the normal state of K3C60 is found to be characteristic of a metal, indicating the important role of the C3–60 ions in the conductivity. From the relaxation measurements, an estimate of the density of electronic states at the Fermi level is derived.

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