Heat capacity of high-purity polycrystalline ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ from 0.4 to 400 K in applied magnetic fields of 0 and 70 kG

The heat capacities C(T) of high-purity polycrystalline pellet and powder samples of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ are reported for the temperature T in the range 0.4 to 400 K. In addition to the feature associated with the onset of superconductivity at ${\mathit{T}}_{\mathit{c}}$≃91 K, two clear anomalies in C(T) for the pellet sample were observed near 74 and 330 K; the origins of the latter two anomalies are unknown, but the temperatures at which they occur are similar to those at which anomalies are seen in the temperature-dependent magnetization M(T). The feature in M(T) at ≃70 K increases linearly with field H at a rate of 0.30 K/kG for 20 kG≤H≤40 kG. The anomaly in C(T) at ≃330 K observed for the pellet was not observed for the powder sample, which is consistent with the lack of an anomaly in M(T) near this temperature for the powder sample. For the pellet sample, the electronic entropy near ${\mathit{T}}_{\mathit{c}}$, the contribution of superconducting fluctuations to C(T) near ${\mathit{T}}_{\mathit{c}}$, and the influence of a 70-kG magnetic field on C(T) near ${\mathit{T}}_{\mathit{c}}$ and below 10 K are analyzed and discussed.