We report on a pressure(P )-induced evolution of superconductivity and spin correlations in CeIrIn5 via the 115 In nuclear-spin-lattice-relaxation rate measurements. We find that applying pressure suppresses dramatically the antiferromagnetic fluctuations that are strong at ambient pressure. At P = 2.1 GPa, Tc increases to Tc = 0.8 K that is twice Tc(P = 0 GPa), in the background of Fermi liquid state. This is in sharp contrast with the previous case in which negative, chemical pressure (replacing Ir with Rh) enhances magnetic interaction and increases Tc. Our results suggest that multiple mechanisms work to produce superconductivity in the same compound CeIrIn5.The cerium (Ce)-based heavy-fermion compounds CeMIn 5 (M = Co, Rh, and Ir) discovered a few years ago provides a unique opportunity to investigate the interplay between antiferromagnetism and superconductivity [1,2,3]. Among CeMIn 5 , CeIrIn 5 and CeCoIn 5 show superconductivity at P = 0 below T c = 0.4 K and 2.3 K, respectively [2,3]. Antiferromagnet CeRhIn 5 becomes superconducting at relatively lower critical pressure P c ∼ 1.6 GPa and yet exhibits a higher T c ∼ 2 K [1]. Measurements of nuclear-quadrupole-resonance (NQR) [4,5,6,7], thermal transport and heat capacity [8] on CeMIn 5 found that the superconductivity is unconventional, with line-nodes in the superconducting gap function. NQR [4,5,7,9] and inelastic neutron diffraction [10] measurements also found strong antiferromagnetic spin fluctuations in the normal state. In addition, in CeIrIn 5 , the antiferromagnetic spin fluctuations are found to be anisotropic [4], namely, a magnetic correlation length ξ plane within the tetragonal plane grows up more dominantly than ξ c along the c-axis associated with their two-dimensional crystal structure. The nuclearspin-lattice-relaxation rate(1/T 1 ) was found to follow the relation of 1/T 1

We present a systematic 115 In NQR study on the heavy fermion compounds CeRh 1−x Ir x In 5 (x=0.25, 0.35, 0.45, 0.5, 0.55 and 0.75). The results provide strong evidence for the microscopic coexistence of antiferromagnetic (AF) order and superconductivity (SC) in the range of 0.35 ≤ x ≤ 0.55. Specifically, for x=0.5, T N is observed at 3 K with a subsequent onset of superconductivity at T c =0.9 K. T c reaches a maximum (0.94 K) at x=0.45 where T N is found to be the highest (4.0 K).Detailed analysis of the measured spectra indicate that the same electrons participate in both SC and AF order. The nuclear spin-lattice relaxation rate 1/T 1 shows a broad peak at T N and follows a T 3 variation below T c , the latter property indicating unconventional SC as in CeIrIn 5 (T c =0.4 K). We further find that, in the coexistence region, the T 3 dependence of 1/T 1 is replaced by a T -linear variation below T ∼0.4 K, with the value (T 1 ) Tc (T 1 ) low−T increasing with decreasing x, likely due to low-lying magnetic excitations associated with the coexisting magnetism.

No abstract

No abstract