New spin injection scheme based on spin gapless semiconductors: A first-principles study.

Spin injection efficiency based on a conventional and/or half-metallic ferromagnet/semiconductor is greatly limited by the Schmidt obstacle due to conductivity mismatch; here we proposed that by replacing the metallic injectors with spin gapless semiconductors can significantly reduce the conductive mismatch to enhance spin injection efficiency. By performing first-principles calculations based on superlattice structure, we have studied a representative system of Mn₂CoAl/semiconductor spin injector scheme. The results showed that a high spin polarization was maintained at the interface in systems of Mn₂CoAl/Fe₂VAl constructed with (100) interface and Mn₂CoAl/GaAs with (110) interface, and the latter is expected to possess long spin diffusion length. Inherited from the spin gapless feature of Mn₂CoAl, a pronounced dip was observed around the Fermi level in the majority spin density of states in both systems, suggesting fast transport of the low-density carriers. [ABSTRACT FROM AUTHOR]