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 300K is estimated to be 1.68 +/- 6.03 ns and monotonically increased with decreasing temperature down to 100K. Below 100K, 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 100K and a weak temperature dependence below 100K. 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 X 10(-6), which is more than two orders of magnitude smaller than that of copper.