Study of half-metallic ferromagnetism in V-doped CdTe alloys by using first-principles calculations

摘要

For investigating the structural, electronic and magnetic properties of zincblende (ZB) Cd_(1-x)V_xTe (0≤x≤l), we have employed the Wu-Cohen generalized gradient approximation (WC-CGA) and the modified Becke and Johnson local density approximation (mBJLDA) functionals within the frame-work of spin polarized density functional theory (DFT). The former exchange-correlation parameterization scheme has been used for optimizing the equilibrium structural properties, while the electronic band structures, electron density of states (DOS) and charge densities are computed using both functionals and their performances are compared. Our results show that the electron spin polarization in unfilled V-3d orbitals gives rise to spin exchange splittings (△_x(d) and △_x(pd)) which is the cause of half metallic (HM) ferromagnetism in the V-doped CdTe as revealed by the computed DOS. Consequently, the nature of effective potential is more attractive in spin-down case rather than that in spin-up case. The total magnetic moment for each of the compounds under study is 3_(μB) where the main contribution comes from the V atom, while the nonmagnetic sites Cd and Te are also bestowed with minor atomic magnetic moments due to Te-5p-V-3d hybridization. Furthermore, we calculated the exchange constants N_oα and N_oα to determine the conduction and valence band contributions in exchange splitting process. A comparison of the two functionals, considered in this work, shows that the mBJLDA provides a better description of the electronic structure especially of the ferromagnetic Cd_(1-x)V_xTe (0.75≤x≤l). Moreover, as compared to WC-GGA, the mBJLDA predicts high Curie temperatures in V-doped CdTe by providing significantly larger values of △_x(d), △_x(pd), N_oα, N_oβ and, importantly, a quite wide HM gap.