Specific heat of bccHe3

Abstract

The specific heat of bcc ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been measured at five molar volumes between 21.5 and 24.5 ${\mathrm{cm}}^3$ and for temperatures between 50 mK and the melting curve. The data below 0.5 K show no evidence of the large anomalous contribution to the specific heat which has been observed in all previous measurements, indicating that this anomaly is not due to an intrinsic property of this quantum solid. Values of the nuclear exchange energy derived from the low-temperature data are in good agreement with values determined by others from various types of measurements. The specific-heat data above approximately 0.5 K are in agreement with previous results and show the large contribution which is generally attributed to thermally activated vacancies. Because of the absence in the present work of the low-temperature anomaly, however, the temperature dependence of the vacancy contribution could be determined more accurately than was previously possible. The measured vacancy contribution shows significant deviations from the expected behavior.