Strain-Induced Half-Metallicity of Alkaline-Earth Alloyed Zinc-Blende SiC and GaN

Using first-principles calculations within generalized gradient approximation, the electronic and magnetic properties of zinc-blende (Si, AE)C and (Ga, AE)N (AE = Mg, Ca, Sr and Ba) superlattice are investigated. We focus on two simple layer-by-layer delta doping structures with the alkaline earth substituting along the (1 0 0) planes and (0 0 1). Ga0.5Ca0.5N, Ga0.5Sr0.5N, Ga0.5Ba0.5N and Si0.5Ca0.5C are found to be half-metallic ferromagnets according to our calculations. Meanwhile, GaN substrates with Ca- or Sr- show robust half-metallicity property. The electronic structures revealed that the zinc-blende Si0.5Sr0.5C have a tendency to exhibit half-metallicity on the isotropic strain; however, Ga0.5Ca0.5N and Ga0.5Sr0.5N superlattices became half-metal when the biaxial strains were imposed. Furthermore, phase transitions from AFM to FM states are also considered for the strain of Ba-alloyed GaN and Mg-alloyed SiC. This study provides a general picture of the magnetic and half-metallic properties of alkaline earth-alloyed SiC and GaN thin films, which is helpful in exploring half-metallic ferromagnets in future.