Temperature Dependence of the Far-Infrared Reflectivity of Magnesium Stannide

The reflectivity of pure samples of magnesium stannide has been measured in the infrared region from 50 to 370 ${\mathrm{cm}}^{-1\mathrm{}}$ at temperatures from 100 to 600°K. The reflection spectra have been analyzed by means of a fit with a classical dispersion formula including Drude terms for the free-carrier effects. At low temperatures the influence of the lattice dispersion on the reflectivity dominates, while at high temperatures the free-carrier effects dominate. The electrical properties of ${\mathrm{Mg}}_2$Sn in the intrinsic conduction range as determined from the reflectivity are in good agreement with the data obtained by Busch and Winkler from electrical measurements.