Suitability of Fe/GaAs and (Co,Ni)Mn(Ga,Ge) for Spintronics Applications: An Ab Initio Study

In this paper, we use density functional theory to compare the usability of Fe(110)/GaAs(110) and new materials like the magnetic Heusler compound Co₂MnGe or Ni₂MnGa for spintronics applications. One quantity, which can easily be obtained and which is of major interest, is the degree of spin polarization at the Fermi level for the different systems under consideration. Therefore, we compare the spin polarization at the Fermi level for different configurations. For a Fe-GaAs multilayer system, a spin polarization of 19.6% is achieved at the interface, which increases towards the bulk polarization of Fe within a few monolayers. But, if only 1/4 monolayer of Fe is covering the GaAs surface, a strong ionic relaxation modifies the density of states, and thus, destroys the spin polarization. The Co₂ MnGe/MgO multilayer system shows an even larger polarization of 60.7% at the interface. Although a martensitic transformation shifts the pseudogap towards the Fermi level for the Ni₂ MnGa system, Co states close this gap.