First-principles Study Of Transition Metal Atoms Doped With ZnS

The 100%spin polarization of Half-metallic(HM)material made it to be a promising material for the future spintronic applications.The materials have two different spin bands.One spin channel crosses the Fermi level EF which is a sign of metallic character,the other spin channel exhibit the semiconducting or Insulatoring characters.HM materials can be classified according to the different properties,such as the crystal structure,the magnetic properties and the origin of the HM nature,and so on.Studies have shown that transition metal(TM)doped ZnS system exhibits a HM character.In this paper,the structural,electronic,magnetic and optical properties of TM atom-doped ZnS systems are investigated within the density functional theory(DFT)using the Vienna ab initio simulation package(VASP)with the projector augmented-wave(PAW)pseudopotential.We find that Mo-doped zinc-blende ZnS exhibits a HM character.When the content of Mo in the zinc-blende ZnS is 25at%,the total magnetic is nearly 4.00 ?B for Zn0.75Mo0.25S,which mainly originates from the Mo atom and a few contributions from the nearest neighboring S atoms and next-nearest neighboring Zn atoms.The ZnS,ZnSe and ZnTe are typical ?-? semiconductors thus have a deeper investigation of the instructual,electronic and magnetic properties of the Zn0.75MoO25M(M=S,Se and Te)with the content of Mo of 25at%.The results indicate that the equilibrium lattice constants are 5.535,5.836 and 6.274 A for M=S,Se and Te,respectively.Such an increasing order is related to the increasing atomic radius of 1.09,1.22 and 1.42 A for S,Se and Te atoms successively.The Zn0.75Mo0.25M system exhibits a HM character,since only one spin channel crosses the Fermi level EF while the other spin channel opens a band gap.In this paper,we systematically investigate the electronic and magnetic properties of not only a single TM atom but also two identical TM atoms X(X=V,Cr,Mn,Fe,Co and Ni)doped ZnS systems.We take X to make a comparison among different TM atoms as well as survey the influence of separation distances between two identical TM atoms.Combining the valance electronic configurations of the TM atoms,we analyze the ferromagnetic and antiferromagnetic coupling between two identical TM atoms X in detail from the double-exchange and superexchange mechanisms.For a single TM atom V,Cr,Mn,Fe,Co or Ni doped ZnS,a magnetic HM character is obtained for the V,Cr,Fe or Ni doped ZnS systems,while a magnetic semiconducting character is obtained for the Mn or Co doped ZnS system.For two identical TM atoms doped ZnS systems,we pay more attention on the effects of separation distances of the two doped TM atoms on their coupling states and from energy minimization we find that two V,Cr or Ni atoms doped ZnS systems are HM with ferromagnetic coupling and two Mn or Co atoms doped ZnS systems are semiconductors with antiferromagnetic coupling regardless their separation distances,while two Fe atoms doped ZnS system is metal with antiferromagnetic coupling at the nearest separation of two Fe atoms and HM with ferromagnetic coupling at the farther separations of two Fe atoms.