Elastic Moduli and Magnetic Susceptibility of MonocrystallineNb3Sn

Abstract

The elastic moduli $c_{11}$, $c_{12}$, and $c_{44}$ and the magnetic susceptibility $\chi$ of single-crystal ${\mathrm{Nb}}_3$Sn have been measured as a function of temperature below 300 K. Detailed comparison is made between the experimental results and the predictions of simple one-dimensional band models. It is found that the behavior of the elastic moduli $c_{11}$ and $c_{12}$ above and below the cubic-tetragonal transformation at 45 K is well accounted for by the band model with an effective Fermi temperature of 80 K. Unlike the case of ${\mathrm{V}}_3$Si, the modulus $c_{44}$ is observed to undergo a considerable softening at low temperatures. This softening is not predicted by the theory. The susceptibility displays the predicted maximum near the lattice-transformation temperature. However, the decrease of $\chi$ in the tetragonal state, associated with a drop in the electronic density of states, is not nearly as large as expected. Furthermore, the cubic-state $\chi$ data indicate a much larger Fermi temperature (230 K) than is obtained from the $c_{11}$ and $c_{12}$ data. We review these anomalies in terms of available band-structure calculations. The implications of our experimental results for superconductivity in ${\mathrm{Nb}}_3$Sn are discussed.