Heat capacity ofYBa2Cu3O7−δat the superconducting transition temperature

The specific heat of a single phase sample of $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ is measured over the temperature range 3-400 K, revealing a discontinuity at $T_c$ of $\frac{\Delta C_p}{T_c}=55\mathrm{}$ mJ ${\mathrm{}(\mathrm{mole}\mathrm{f}.\mathrm{u}.\mathrm{})\mathrm{}}^{-1\mathrm{}}$ ${\mathrm{K}}^{-2\mathrm{}}$, where mole f.u. denotes mole formula unit. Magnetic susceptibility measurements give a temperature-independent contribution of 3.06×${10}^{-4\mathrm{}}$ emu ${\mathrm{}(\mathrm{mole}\mathrm{f}.\mathrm{u}.\mathrm{})\mathrm{}}^{-1\mathrm{}}$. These two measurements suggest that $\frac{\Delta C_p}{\gamma T_c}$ is near the weak-coupling BCS value of 1.43. Comparable measurements reported by other investigators on this compound and on ${\mathrm{La}}_{1.85}$ ${\mathrm{Sr}}_{0.15}$Cu${\mathrm{O}}_4$ are cited and discussed.