C13 NMR Investigation of the Superconductor MgCNi3 up to 800 K

We report (13)C NMR characterization of the new superconductor MgCNi(3) [T. He et al., Nature (London) 411, 54 (2001)]. We found that both the uniform spin susceptibility and the spin fluctuations show a strong enhancement with decreasing temperature, and saturate below approximately 50 K and approximately 20 K, respectively. The nuclear spin-lattice relaxation rate 1/(13)T(1) exhibits typical behavior for isotropic s-wave superconductivity with a coherence peak below T(c) = 7.0 K that grows with decreasing magnetic field.