Spin-Injection into GaAs using ferromagnetic (Ga,Mn)As contacts

In our work we have employed a successful all electrical and all semiconductor spin injection scheme. Our samples base on a new class of so-called diluted magnetic semiconductors, namely its best known representative GaMnAs. In our experiments we were able to reliably achieve spin injection efficiencies of remarkably high 50% and slightly above. The results obtained from nonlocal in-plane spin-valve measurements were thereby consistent with our out-of-plane Hanle experiments in terms of injection efficiencies as well as spin diffusion lengths. These were roughly 3 µm, what corresponds to a spin lifetime in the range of 5 ns. We additionally investigated the anisotropies of tunneling MR and spin polarization. For in-plane TAMR we gained values of up to ≈ 1.5 % while for out-of-plane configuration we observed ≈ 8 %. In the case of in-plane TASP the effect had a magnitude of ≈ 8% and the out-of-plane TASP reached ≈ -25 %. For a second wafer with slightly lower doping of the conduction channel and thicker GaMnAs the spin diffusion length easily exceeded 10 µm. Our experiments on this second wafer have confirmed that a lithographically induced control of magnetic anisotropies in GaMnAs is possible due to strain relaxation of the GaMnAs layer perpendicular to the structure edges.