Sign determination of spin polarization inL21-orderedCo2FeSiusing a Pt-based spin Hall device

Abstract

So far, we have demonstrated markedly high spin polarizations ($\ensuremath{\sim}0.8$) in one of the $L{2}_{1}$-ordered Heusler compounds, ${\mathrm{Co}}_{2}\mathrm{FeSi}$ (CFS), by detecting pure spin currents using nonlocal spin-valve measurements. Here, we experimentally determine the sign of the spin polarization in the $L{2}_{1}$-ordered CFS using the electrical spin Hall effect (SHE) measurements in a lateral device with Pt. Inverse SHE signals with a positive-sign hysteresis loop are clearly detected at 20 K. Since the spin Hall conductivity of Pt is the positive sign, the pure spin current generated by the CFS electrode with $L{2}_{1}$-ordered structures has positive spin polarization. The SHE measurement is a powerful tool to determine the sign of the spin polarization in unknown spin injectors.