Superconducting state magnetization and critical fields of single- crystal YNi 2B 2C

Abstract

Single crystals of YNi 2B 2C have been grown via high-temperature flux growth, using Ni 2B as a solvent. Magnetization measurements have been carried out over a large portion of the magnetic field-temperature plane on a single crystal of YNi 2B 2C for field applied parallel to the c-axis in order to determine the range of thermodynamic reversibility and the critical magnetic fields. The magnetization is thermodynamically reversible within 2% of the magnetization for fields above 0.5 T and temperatures above 3 K. Near T c, the upper critical field has a slope of -0.32 T/K. The zero-temperature Ginzburg-Landau parameter κ is 13≈15, the penetration depth λ ab is about 150 nm, and the coherence distance λ ab is about 10 nm. The irreversibility line H irr ( T) obeys H irr ( T) = H irr (0) (1- T/ T c) 1.16. The magnetization data below T c closely follow a logarithmic dependence on applied field, in the intermediate region, as predicted by the London model. The magnetization versus temperature curves shift uniformly to lower temperature as the field increases. Based on these measurements, YNi 2B 2C seems more similar to conventional low- T c superconductors than to high- T c superconductors.