The heat capacity of high-purity gadolinium from 0.5 to 4 K and the effects of interstitial impurities

Two sets of experiments are presented. In the first, the effects of interstitial impurities on the heat capacity are explored in a gadolinium specimen of moderate purity. The second set consists of measurements on a number of samples of the highest available purity prepared by the solid-state electrotransport process. The heat capacities of the two highest-purity specimens are found to agree to 1% or better, and that of the most pure specimen can be represented by the expression C p =4.48T+1.37T 1.5 +0.404T 3 mJ K -1 mol -1 implying that the electronic specific heat coefficient gamma =4.48+or-0.07 mJ K -2 mol -1 and the Debye temperature theta 0 =169+or-1 K. The quoted errors are standard deviations derived from the scatter in the experimental points, and do not include systematic errors; these are discussed in the text.