CO-59 NQR STUDY IN SUPERCONDUCTING CECO2

We have performed Co-59 NQR study in superconducting CeCo2 with T-c si milar to 1.4 K in order to investigate the superconducting property. N uclear spin-lattice relaxation of Co, 1/T-1 was measured down to 150 m K. 1/T-1 is proportional to temperature (T) in the normal state, and d ecreases exponentially in the superconducting state with the Hebel-Sli chter peak just below T-c. T-dependence of 1/T-1 in the superconductin g state is a typical feature of s-wave superconductivity with 2 Delta/ k(B)T(c) similar to 2.26, which is remarkably smaller than 3.5 in the BCS superconductor.