SPECIFIC HEAT OF NIOBIUM-TIN

The specific heat of Nb3Sn has been measured over the temperature range 1-42°K, and in magnetic fields up to 52.5 kG. The data can be interpreted to give =13.1 mJ/g atom°K2, CTc=2.4, H0=5350 G, and (Tc)=21.7. The Debye temperature appears to increase at the rate of 1°K/°K over most of the range of the measurements, with (0)=228K. Measurements have also been made on a sample of composition Nb4Sn, and on vapor-grown Nb3Sn similar to that exhibiting the cubic-tetragonal lattice transformation. The specific heat of Nb3Sn can be reconciled with elastic-constant data only if it is assumed that the lattice softening implied by the decreasing velocity of sound with decreasing temperatures is limited to frequencies considerably below the Debye frequency. © 1968 The American Physical Society.