Thermal Conductivity of Dysprosium, Erbium, and Lutetium Single Crystals

The thermal conductivity of dysprosium, erbium, and lutetium single crystals has been measured as a function of temperature from 5° to 300°K. Measurements were made along the 〈0001〉 (c axis) direction and along a basal plane direction. Electrical resistivity measurements were made on the same crystals so that the Lorenz functions could be calculated. The magnetic transitions in dysprosium and erbium produced a pronounced effect on the c‐axis thermal conductivity. With increasing temperature a precipitous drop occurred at the ferromagnetic‐antiferromagnetic transition. A sharp rise occurred as the antiferromagnetic‐paramagnetic transition was approached. Only slight effects were seen in the basal plane measurements. The results were interpreted on the basis of magnetic superzone energy gaps. The thermal conductivity of nonmagnetic lutetium showed a temperature dependence similar to non‐rare earth metals. The Lorenz‐function values were considerably higher than expected for pure electronic heat transport in...