Investigation of spin scattering mechanism in silicon channels of Fe/MgO/Si lateral spin valves

The temperature evolution of spin relaxation time, {\tau}sf, in degenerate silicon (Si)-based lateral spin valves is investigated by means of the Hanle effect measurements. {\tau}sf at 300 K is estimated to be 1.68+-0.03 ns and monotonically increased with decreasing temperature down to 100 K. Below 100 K, in contrast, it shows almost a constant value of ca. 5 ns. The temperature dependence of the conductivity of the Si channel shows a similar behavior to that of the {\tau}sf, i.e., monotonically increasing with decreasing temperature down to 100 K and a weak temperature dependence below 100 K. The temperature evolution of conductivity reveals that electron scattering due to magnetic impurities is negligible. A comparison between {\tau}sf and momentum scattering time reveals that the dominant spin scattering mechanism in the Si is the Elliott-Yafet mechanism, and the ratio of the momentum scattering time to the {\tau}sf attributed to nonmagnetic impurities is approximately 3.77*10^-6, which is more than two orders of magnitude smaller than that of copper.