Disorder and/or density of states effect in YxLu1-xNi2B2C

The role of disorder and/or lattice strain due to the size mismatch between Y and Lu in the solid solution YxLu1-xNi2B2C was studied by specific heat measurements in magnetic fields up to 9 T. Thereby, the analysis of the sup erconducting and normal state heat capacity as well as the temperature depe ndence of the upper critical field H-c2 shows that the reported reduction o f T-c within the solid solution correlates with a reduction of the electron ic density of states N(E-f). Thus, the major effect of Y/Lu substitution up on superconductivity is due to a band broadening arising from the R-ion siz e mismatch rather than from disorder scattering of Cooper electrons. (C) 20 00 Elsevier Science B.V. All rights reserved.