NMR and NQR studies of the heavy fermion superconductors CeTIn5 (T = Co and Ir) - art. no. 134526

We have carried out In-115 and Co-59 nuclear quadrupole resonance and nucle ar magnetic resonance measurements on CeCoIn5 and CeIrIn5. The temperature T dependence of the nuclear spin-lattice relaxation rate 1/T-1 of In-115 in the normal state indicates that CeCoIn5 is located just at art antiferroma gnetic instability, and CeIrIn5 is in the nearly antiferromagnetic region. In the superconducting state, 1/T-1 has no Hebel-Slichter coherence peak ju st below T-C and a power-law T dependence (close to T-3) at very low temper atures, which indicates the existence of line nodes in the superconducting energy gap. The In-115 (Ce-In plane) Knight shift in CeCoIn5 decreases for both parallel and perpendicular directions to the tetragonal c axis in the superconducting state, which shows that the spin susceptibility decreases i n all directions. These results indicate that CeCoIn5 and CeIrIn5 exhibit n on-s-wave even parity (probably d-wave) superconductivity.