Effective Mass in Gray Tin from Knight Shift Measurements

The nuclear magnetic resonance of Sn¹¹⁹ in gray tin was measured between 200^∘{}K and 300^∘{}K and the effective g factor was found to increase by about 4 parts in 10⁵ over this temperature range. This increase in Knight shift is thought to arise from an increase in the number of conduction electrons. By combining this result with Busch and Mooser's measurements of the magnetic susceptibility over the same temperature range mₗ, the single-valley effective mass of the lighter of the charge carriers, is found to be (0.3±0.05)m if the electron g factor is 2. The experiment also allows one to determine the Knight shift without making a comparison with a diamagnetic substance. The Knight shift of intrinsic gray tin is found to be 6×{}10^-5 at 300^∘{}K. The fact that the Knight shift is positive shows that the electron g factor is not negative as would be expected if the band structure of gray tin were similar to that of InSb.