First-principles study of spin-polarized electronic band structures in ferromagnetic Zn1-xTMxS (TM = Fe, Co and Ni)

We report a first-principles study of structural, electronic and magnetic properties of crystalline alloys Zn1-xTMxS (TM = Fe, Co and Ni) at x = 0.25. Structural properties are computed from the total ground state energy convergence and it is found that the cohesive energies of Zn1-xTMxS are greater than that of zincblende ZnS. We also study the spin-polarized electronic band structures, total and partial density of states and the effect of TM 3d states. Our results exhibit that Zn0.75Fe0.25S, Zn0.75Co0.25S and Zn0.75Ni0.25S are half-metallic ferromagnetic with a magnetic moment of 4 mu(B), 3 mu(B) and 2 mu(B), respectively. Furthermore, we calculate the TM 3d spin-exchange-splitting energies Delta(x)(d), Delta x(x-d), exchange constants N-0 alpha and N-0 beta, crystal field splitting (Delta E-cryst = E-t2g - E-eg), and find thatp-d hybridization reduces the local magnetic moment of TM from its free space charge value. Moreover, robustness of Zn1-xTMxS with respect to the variation of lattice constants is also discussed. (c) 2010 Elsevier B.V. All rights reserved.