Spin injection and detection up to room temperature in Heusler alloy/ n -GaAs spin valves

We have measured the spin injection efficiency and spin lifetime in Co2FeSi/n-GaAs lateral nonlocal spin valves from 20 to 300 K. We observe large (∼40μV) spin valve signals at room temperature and injector currents of 103A/cm2, facilitated by fabricating spin valve separations smaller than the 1μm spin diffusion length and applying a forward bias to the detector contact. The spin transport parameters are measured by comparing the injector-detector contact separation dependence of the spin valve signal with a numerical model accounting for spin drift and diffusion. The apparent suppression of the spin injection efficiency at the lowest temperatures reflects a breakdown of the ordinary drift-diffusion model in the regime of large spin accumulation. A theoretical calculation of the D'yakonov-Perel' spin lifetime agrees well with the measured n-GaAs spin lifetime over the entire temperature range.