Point-contact spectroscopy of superconducting energy gap in DyNi2B2C

The superconducting energy gap in DyNi2B2C has been investigated using a po int-contact technique based on the Andreev reflection from a normal (N)-sup erconductor (S) boundary, where N is Ag. The observed differential resistan ce dV/dl is well described by the Blonder-Tinkham-Klapwijk (BTK) theory bas ed on the BSC density of states with zero broadening parameter. Typically, the intensity of the gap structure amounts to several percentage of the nor mal state resistance, which is an order of magnitude less than predicted by the theory. For DyNi2B2C with T-c < T-N (the Neel temperature), we found g ap values satisfying the ratio of 2 Delta(0)/k(B)T(c) = 3.63 +/- 0.05 simil ar to other superconducting nickel-borocarbides, both nonmagnetic and magne tic with T-c greater than or equal to T-N. The superconducting gap nonlinea rity is superimposed on the antiferromagnetic structure in dV/dl(V) which i s suppressed at the magnetic field of the order of 3 T applied nominally in the ab-plane and temperature greater than or equal to 11 K. The observed s uperconducting properties depend on the exact composition and structure at the surface of the crystal. (C) 2000 Published by Elsevier Science B.V. All rights reserved.