Enhancement ofTcin CeIr(In1–xCdx)5studied by In-NQR

We report on superconducting nature under pressure in CeIr(In1–xCdx)5 by In-Nuclear-Quadrupole-Resonance (NQR) studies. In CeIr(In0.925Cd0.075)5, the inhomogeneous antiferromagnetic order at TN ~ 2.3 K is induced by Cd-dopants and superconductivity disappears at ambient pressure. However, the measurements of a nuclear-spin-lattice-relaxation rate 1/T1 have revealed that the superconductivity suddenly occurs above 2.1 GPa. It is observed that the superconducting gap is enhanced in the Cd-doped sample, indicating that the Cd-doping induces the strong coupling superconductivity leading to the enhancement of Tc in the CeIrIn5 system. Furthermore, we found that the residual density of states at the Fermi level increases with increasing pressure, suggesting that the superconducting nature of CeIrIn5 is quite different from those of CeCoIn5 and CeRhIn5.