Heat Capacity of Thulium from 15° to 360°K

Abstract

Thulium shows a lambda anomaly in its heat capacity near 55°K which is associated with magnetic ordering and which shows thermal hysteresis. In addition, there are anomalous changes in the slope of the heat capacity curve near 88°, 162°, and 180°K. These changes and the unexpectedly low value of the slope near room temperature complicate the analysis of the data, but there is evidence that the effective exchange integral in thulium is appreciably larger than that for neighboring rare earths. The results in the temperature range from 14° to 21°K support a T3 dependence of the magnetic specific heat as predicted by spin wave theory for an antiferromagnet. The thermodynamic functions are tabulated for the temperature range studied.