Probing the electronic band structure of ferromagnets with spin injection and extraction

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We study spin injection and spin extraction signals in lateral spin-valve structures consisting of ferromagnetic Co₂FeSi contacts on n-type GaAs transport channels. The dependence of the spin-valve signals on the bias current is found to strongly depend on the degree of ordering in the Co₂FeSi lattice. For the fully ordered L2₁ phase, the signal is equal for injection and extraction and independent of the bias current. In contrast, a strong dependence of the relative signal strengths (spin injection versus extraction) on the bias current is observed for the partially disordered $B2$ phase. We explain the strongly different behavior by the crucial influence of the respective electronic band structure on the spin generation processes.