We report a study of 13C NMR spin-lattice relaxation in the superconducting fulleride K3C60 at low temperatures (T). The experimentally obtained relaxation data, which are scaled to a T-independent relaxation shape, are found to be well reproduced by the anisotropy parameter αspin ≡ Aisospin/Aaxspin, where Aisospin and Aaxspin are the isotropic and anisotropic part of the 13 C hyperfine coupling of conduction electrons, respectively. Simulation for a powder sample with various αspin values indicates that the deviation from a single-exponential relaxation is largest when the hyperfine coupling is isotropic to some extent (i.e., αspin ≈ 0.5) instead of purely anisotropic (i.e., αspin = 0). These results justify a model based on the electronic single site. Moreover, from the validity of the extended Korringa relation with K(α) = 5.7, it is found that the electronic state is a Fermi liquid in which the relaxation rate is enhanced substantially by the antiferromagnetic electron interaction.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)