B-11 and Pt-195 NMR studies in the normal state of substituted borocarbide superconductors Y0.98Er0.02Ni2B2C and LaPt1.5Au0.6B2C

Abstract

We report, B-11 NMR studies on Y0.98Er0.02Ni2B2C and B-11 and Pt-195 NMR studies on LaPt1.5Au0.6B2C superconductors. The variation of (1/T1T) with temperature in the normal state of Y0.98Er0.02Ni2B2C shows a similar behaviour as in YNi2B2C. However, its magnitude is one order more than that observed in YNi2B2C. This suggests that T-1 is dominated by the thermal fluctuations of Er local moments in this case. From B-11 and Pt-195 NMR in LaPt1.5Au0.6B2C, we demonstrate that the Pt 5d band is full and the compound exhibits Korringa behaviour as expected for a normal Fermi-liquid. This is in contrast to YNi2B2C where an enhancement of the B-11 (1/T1T) is observed at low temperatures along with a deviation from Korringa behaviour, suggesting that the enhancement seen in YNi2B2C could be due to the anti-ferromagnetic fluctuations from nickel 3d-electrons.