Depression of the superconducting transition temperature of the Heusler alloyPd2YSn with the addition of magnetic rare-earth metals

The compound ${\mathrm{Pd}}_2$YSn, having the cubic Heusler L$2_1$ structure, is superconducting with a transition temperature ($T_c$) of 4.55 K. The effect on $T_c$ of replacing Y by other magnetic rare-earth metal has been investigated in the series ${\mathrm{Pd}}_2$ ${\mathrm{Y}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{R}}_{\mathrm{x}}$Sn (R=Gd, Dy, Ho, Er, Tm, and Yb). The depression in $T_c$ is the largest with Gd substitution. The initial rate of depression of $T_c$ shows deviation from the de Gennes function. The results of $T_c$ measurements are analyzed in terms of Abrikosov-Gor’kov theory, taking into account the effects of crystalline electric fields acting on rare-earth ions. Values of the density of states times the exchange constant, [N(0)$J_{\mathrm{sf}{}^2}$], are derived from these measurements.