Electronic Structure And Magnetism Of Cobalt Doped ZnO Dilute Magnetic Semiconductor

With the quantum mechanics and solid theory continuous improvement as well as therapid development of computer performance, using the materials simulationsoftware to predicate new material becomes more mature. In this paper, magneticproperties and electronic structure of Co-doped ZnO-based magnetic semiconductors areinvestigated based on density functional theory.To verify the feasibility of the method, this paper optimizes the structure of Co-dopedZnO and compares the degree of lattice distortion. The electronic structure and magneticproperties show that Co-doped ZnO is a semi-metal structure. The Co-3d electronic states inthe tetrahedral crystal field of the O atoms split into a double e state and the two threefold t2gstate. The Co atom has a spin polarization near the Fermi level.For the two Co atoms doped ZnO, the calculation total energy difference of theferromagnetic and antiferromagnetic, confirmed the total energy of ferromagnetism lower, soCo-doped ZnO is ferromagnetic stability. The magnetic of the material come from thecoupling of the two Co atoms through mediating of the O atom.Oxygen vacancies and zinc interstitial defects are the more common p-type defects inCo-doped ZnO system. This paper studies the effect of defects on the electronic structure andmagnetic properties. Oxygen vacancy (Vo) defect generated more easily in the close NeighborCo atoms. Oxygen vacancy makes the valence band to shift toward the Fermi level, whichbring at the larger spin polarization at the Fermi level. The introduction of Vo makes thetetrahedral crystal to generate a huge asymmetry, which make the Co atom in the crystal fieldto split increase and make the strengthening of the spin polarization. This provided thepreconditions for the generation of magnetic materials.Oxygen vacancy only effectsthe coupling between the neighbor Co atoms and less impact on the two far Co atoms. Whenthe two Co atoms neighbors, Vo is located in the middle of the two Co atoms, theantiferromagnetic are more stable; When Vo is located the one Co side, the ferromagnetism ismore stable; But when the two Co remote presence and Vo far from the Co atom, theantiferromagnetism is more stable. The introduction of oxygen vacancies also makes theCo atomic magnetic moment reduced, which due to Co atoms absorption the electrons.The introduction of Zni defects makes the crystal structure to produce a large distortion,which make Co to split more pronounced in the crystal field and Co atom near the Fermi levelwith a strong spin polarization. Obtained by optimizing the Zni easier existin the octahedral, the electronic of Zni introduction transfer between the Co atoms and Oatoms, thus affecting the magnetic moment.