Superconducting and magnetic properties of Sr3Ir4Sn13

Magnetization and muon spin rotation and relaxation (mu SR) measurements have been performed to study the superconducting and magnetic properties of Sr3Ir4Sn13. From magnetization measurements the lower and upper critical fields T = 0 K are found to be 8.5(1) mT and 1.44(2) T, respectively. Zero-field mu SR data show no sign of any magnetic ordering or weak magnetism. Transversefield mu SR measurements in the vortex state provide the temperature dependence of the magnetic penetration depth lambda. The temperature dependence of lambda(-2) is consistent with the existence of a single s-wave energy gap in the superconducting state of Sr3Ir4Sn13 with a gap value of 0.82(2) meV at absolute zero temperature. However, a two-gap s + s-wave model fit with gap values of 0.91(4) and 0.14(7) meV cannot be ruled out completely. The magnetic penetration depth at zero temperature. lambda(0) is 291(3) nm. The ratio Delta(0)/k(B)T(c) = 2.1(1) indicates that Sr3Ir4Sn13 should be considered a strong-coupling super-conductor.