Thermal Conductivity of High-Purity Iron at Low Temperatures

Thermal conductivity (λ) of a high-purity iron (99.998+% Fe) has been studied as a function of temperature (T) between 7° and 200°K. The λ vs T curve reaches a maximum of about 15 W-cm−1 °K−1 at 21°K. This value is considerably larger than that of 4.5 W-cm−1 °K−1 observed before by Kemp et al. in 1959. Our measurements are in qualitative agreement with the theoretical expectations for a high-purity iron. The problem, associated with accurate determination of the Lorenz number and the thermal resistivity due to electron-phonon scattering at low temperatures in iron, is briefly discussed.