Thermal and Electrical Transport Properties of High Purity Single Crystal Beryllium

Abstract

Measurements of the electrical resistivity and thermal conductivity of a high purity single crystal of beryllium oriented along the c-axis have been made as a function of longitudinal magnetic field (up to 70 KG) and temperature (2 to 35 K). The residual resistivity ratio (RRR) as determined by the eddy-current method is about 2000. Completed results of the temperature dependent zero field thermal conductivity of this sample indicate a sharp peak of 143 watts/cm-K at a temperature of 13.5 K. The zero field electrical resistivity has a residual value of 1.85 × 10−9 ohm-cm, and Wiedmann Franz Lorenz (WFL) behavior typical for most metals is observed, with the residual plateau approaching the Sommerfeld value. A strong saturating magneto-thermal resistance is observed by 40 KG at selected temperatures both above and below the maximum in thermal conductivity. At 8.2 K, 14 K, 19 K and 25 K the thermal conductivity is observed to decrease by 73%, 65%, 58% and 51% respectively. Electrical resistivity is observed to increase by a similar factor, but the accuracy of the resistivity measurements was limited by excessive pickup in the higher field regions. Longitudinal D.C. electrical resistivity measurements give a RRR = 1750 in comparison to the eddy-current method. The same series of measurements are planned for a sample of RRR = 1000. Deviations from Matthiesson’s rule, and the field dependence of the WFL ratio as a function of sample purity will be presented at a later date.