Half-metallicity at the Heusler alloy Co2Cr0.5Fe0.5Al(001) surface and its interface with GaAs(001)

Electronic and magnetic properties of the Heusler alloy Co2Cr0.5Fe0.5Al(001) surfaces and its interfaces with GaAs(001) are studied within the framework of density functional theory by using the plane-wave pseudopotential approach. The phase diagram obtained by ab initio atomistic thermodynamics shows that the CrAl surface is the most stable (001) termination of this Heusler alloy. We discuss that, at the ideal surfaces and interfaces with GaAs, half-metallicity of the alloy is lost, although the CrAl surface keeps high spin polarization. The energy band profile of the stable interface is investigated and a negative p Schottky barrier of -0.78 eV is obtained for this system.