C13 NMR Investigation of the Superconductor MgCNi3 up to 800 K

We report ¹³C NMR characterization of the new superconductor MgCNi₃ [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 ~50K and ~20K, respectively. The nuclear spin-lattice relaxation rate 1/¹³T₁ exhibits typical behavior for isotropic s-wave superconductivity with a coherence peak below Tc0ex0ex=0ex0ex7.0K that grows with decreasing magnetic field.