Nuclear Contribution to the Heat Capacity of Terbium Metal

Abstract

The heat capacity of terbium metal has been measured between 0.25° and 1.0°K. The high temperature data can be expressed as ${\text{C=28R×10}}^{\text{−3}}{\mathrm{/T}}^2$ cal/mole‐deg which is in excellent agreement with the paramagnetic resonance experiments of Baker and Bleaney on terbium ethyl sulfate. The data are compared with a Schottky formula for the heat capacity, assuming equal spacing between the nuclear hyperfine levels with an over‐all spacing of Δ=0.45°K, corresponding to the high temperature expression above. The agreement is within experimental error except at the very lowest temperatures obtained. The effective field at the nucleus of the terbium atom can be calculated and is found to be $H_{\mathrm{eff}}{\text{=4×10}}^6$ gauss.