Temperature dependence of the nonlocal voltage in an Fe/GaAs electrical spin-injection device

The nonlocal spin resistance is measured as a function of temperature in a Fe/GaAs spin-injection device. For nonannealed samples that show minority-spin injection, the spin resistance is observed up to room temperature and decays exponentially with temperature at a rate of 0.018 K(-1). Postgrowth annealing at 440 K increases the spin signal at low temperatures but the decay rate also increases to 0.030 K(-1). From measurements of the diffusion constant and the spin lifetime in the GaAs channel, we conclude that sample annealing modifies the temperature dependence of the spin-transfer efficiency at injection and detection contacts. Surprisingly, the spin-transfer efficiency increases in samples that exhibit minority-spin injection.