The First-principles Study On Half-metallic Ferromagnets Based On ZnO And ZnS

In this thesis, the electronic structures and magnetism of the intrinsic non-magnetic elements carbon-doped zinc-blende zinc oxide and titanium-doped zinc sulfide are investigated using the full-potential linearized augmented plane wave (FP-LAPW) based on the density functional theory (DFT).We find that C-doped zinc-blende ZnO is a half-metallic ferromagnetic semiconductor. When the content of carbon in the zinc-blende ZnO is 6.25at%, the total magnetic moment is 2.00μB for the ZnO1-xCx (x=0.0625), which mainly originates from the carbon atom and a few contributions from the nearest neighboring Zn atoms and next-nearest neighboring O atoms. Furthermore, it indicates C-doped zinc-blende ZnO can induce ZnO to p-type ferromagnetic semiconductors. After investigating the ferromagnetic stability of C-doped zinc-blende ZnO, we find that when the distance between the carbon atoms is adjacent the carbon atoms are prone to form paramagnetic clusters, which is unfavorable to the formation of ferromagnetism, when the distance between the carbon atoms is appropriate, the half-metallic ferromagnet can be achieved. Therefore, we should take some measures to avoid the carbon clusters in the experiment. Finally, the ferromagnetic mechanism is analyzed.Additionally, we carried out the calculations for the electronic structures and magnetism of titanium-doped zinc sulfide in detail. Based on our theoretical calculations, it reveals that the Ti-doped zinc sulfide possesses apparent magnetism. When the content of titanium in the ZnS is 6.25at%, the total magnetic moment is 2.00μB for the ZnS1-xTix (x=0.0625), which mainly originates from the titanium atom. After investigating the ferromagnetic stability of Ti-doped zinc-blende ZnS, we find that the Ti-doped ZnS is prone to form stable ferromagnetic ground state, and its ferromagnetic interaction can be analyzed by using free-ion mediated double exchange. Because zinc, oxygen, sulfide, carbon and titanium are no magnetic, and neither is any compound with (Zn, O, S, C and Ti) ferromagnetic, so the magnetism for C-doped zinc-blende ZnO and Ti-doped zinc-blende ZnS is intrinsic, and both of them are free of magnetic impurity phases. Therefore, they will be promising for developing spintronics devices.