A MU-SR DETERMINATION OF THE PENETRATION DEPTH IN SUPERCONDUCTING YNI2B2C

Muon spin rotation (mu SR) and magnetisation measurements have been used to characterise the superconducting state of YNi2B2C below T-c=15 K. A measured B-c2(0) of 6.0(5) T and B-c1(0) of 36.9(5) mT from magnetisation measurements, together with the mu SR measurements, provide a coherence length, xi(0), of 8.1 nm and a magnetic penetration depth, lambda(0), of 103 nm. The temperature dependence of the penetration depth deduced from the mu SR measurements is consistent with the BCS model and implies conventional s wave pairing in YNi2B2C. Using these results together with existing thermodynamic data we estimate a superconducting carrier density of 1.9 per formula unit and an electron-mass enhancement factor of 9.4.