¹¹B and ¹⁹⁵Pt NMR studies in the normal state of substituted borocarbide superconductors Y_0.98Er_0.02Ni₂B₂C and LaPt_1.5Au_0.6B₂C

Abstract

We report, ¹¹B NMR studies on Y_0.98Er_0.02Ni₂B₂C and ¹¹B and ¹⁹⁵Pt NMR studies on LaPt_1.5Au_0.6B₂C superconductors. The variation of (1/T₁T) with temperature in the normal state of Y_0.98Er_0.02Ni₂B₂C shows a similar behaviour as in YNi₂B₂C. However, its magnitude is one order more than that observed in YNi₂B₂C. This suggests that T₁ is dominated by the thermal fluctuations of Er local moments in this case. From ¹¹B and ¹⁹⁵Pt NMR in LaPt_1.5Au_0.6B₂C, 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 ¹¹B (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.