First-Principles Study of Doped Half-Metallic Spinels: Cu0.5Zn0.5Cr2S4, Cu0.5Cd0.5Cr2S4, Li0.5Zn0.5Cr2O4 and Li0.5Zn0.5Cr2S4

Electronic structure and magnetic properties of Cu0.5Zn0.5Cr2S4, Cu0.5Cd0.5Cr2S4, Li0.5Zn0.5Cr2O4 and Li0.5Zn0.5 Cr2S4 are investigated using the first-principles calculation based on the density functional theory. GGA+U exchange correlation is used in the calculation to correct the effective Coulomb repulsion energy of Cr underestimated by LSDA or GGA. The calculation results reveal that half-metallic Cu0.5Zn0.5Cr2S4 and Cu0.5Cd0.5Cr2S4 can be achieved by doping CuCr2S4 with Zn or Cd, though CuCr2S4 is not half-metallic. Half-metallic LiCr2O4 is experimentally unstable, but half-metallic Li0.5Zn0.5Cr2O4 and Li0.5Zn0.5Cr2S4 can be achieved by doping Li into experimentally stable ZnCr2O4 and ZnCr2S4, though ZnCr2O4 and ZnCr2S4 are not half-metallic. The influence of +U on the electronic structure and half-metallicity of the doped systems is also presented.