Elastic Moduli of Tin at the Superconducting Transition

A composite oscillator technique was used to measure the elastic moduli of tin in the normal and superconducting states. The experiments were performed on single crystals at about 50 kc/sec. A difference in moduli was observed, indicating that the velocity of sound is less in the superconducting than in the normal state. At 3.7°K the relative change at the superconducting transition is about 4 parts in ${10}^6$ for the longitudinal modulus $S_{11}$ and about 6 parts in ${10}^6$ for the torsional modulus, $2(S_{44}+S_{66})$. These relative changes increase with decreasing temperature. At room temperature, the adiabatic modulus $S_{11}$ was found to be 1.55×${10}^{-12\mathrm{}}$ ${\mathrm{cm}}^2$/dyne, and $2(S_{44}+S_{66})$ was 9.4×${10}^{-12\mathrm{}}$ ${\mathrm{cm}}^2$/dyne.