Dominance of the spin-dipolar NMR relaxation mechanism in fullerene superconductors.

Antropov V.P., Mazin I.I., Andersen O.K., Liechtenstein A.I., Jepsen O.

The authors have performed ab initio calculations for the NMR relaxation rate in doped fullerenes and find that the spin-dipolar relaxation mechanism dominates the orbital and Fermi-contact mechanisms. The reason is that the states at the Fermi level are pp pi -like so that the carbon orbitals have almost exclusively radial p character. With the values 7.2 and 8.1 states/(eV spin molecule) for the bare densities of states at the Fermi level for, respectively, K3C60 and Rb3C60, plus the ab initio value 1.7 eV spin C atom for the effective Stoner exchange parameter, good agreement is obtained with the experimental relaxation rates.

Physical Review B, 47 12373-6, 1993.

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