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

Abstract The role of disorder and/or lattice strain due to the size mismatch between Y and Lu in the solid solution Y x Lu 1− x Ni 2 B 2 C was studied by specific heat measurements in magnetic fields up to 9 T. Thereby, the analysis of the superconducting and normal state heat capacity as well as the temperature dependence of the upper critical field H c2 shows that the reported reduction of T c within the solid solution correlates with a reduction of the electronic density of states N ( E f ). Thus, the major effect of Y/Lu substitution upon superconductivity is due to a band broadening arising from the R -ion size mismatch rather than from disorder scattering of Cooper electrons.