Thermal spin injection and accumulation in CoFe/MgO tunnel contacts to n-type Si through Seebeck spin tunneling

We report the thermal spin injection and accumulation in crystalline CoFe/MgO tunnel contacts to n-type Si through Seebeck spin tunneling (SST). With the Joule heating (laser heating) of Si (CoFe), the thermally induced spin accumulation is detected by means of the Hanle effect for both polarities of the temperature gradient across the tunnel contact. The magnitude of the thermal spin signal scales linearly with the heating power and its sign is reversed as we invert the temperature gradient, demonstrating the major features of SST and thermal spin accumulation. We observe that, for the Si (CoFe) heating, the thermal spin signal induced by SST corresponds to the majority (minority) spin accumulation in the Si. Based on a quantitative comparison of thermal and electrical spin signals, it is noted that the thermal spin injection through SST can be a viable approach for the efficient injection of spin accumulation