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

TL;DR

This study demonstrates effective spin injection and detection at room temperature in Heusler alloy/$n$-GaAs spin valves, achieving large signals through optimized device fabrication and biasing, with results supported by numerical modeling and theoretical calculations.

Contribution

It reports the first observation of large spin valve signals at room temperature in Co$_2$FeSi/$n$-GaAs devices, with a detailed analysis of spin transport parameters and model validation.

Findings

Large spin valve signals (~40 μV) at room temperature.

Spin transport parameters match numerical models accounting for drift and diffusion.

Theoretical D'yakonov-Perel spin lifetime agrees with measurements.

Abstract

We have measured the spin injection efficiency and spin lifetime in Co$_2$FeSi/$n$-GaAs lateral nonlocal spin valves from 20 to 300 K. We observe large ($\sim$40 $\mu$V) spin valve signals at room temperature and injector currents of $10^3~$A/cm$^2$, facilitated by fabricating spin valve separations smaller than the 1 $\mu$m 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.