First-Principle Study On The Electronic Structure And Spin Structure Of Half-metallic Ferromagnets

In the past decades, half-metallic ferromagnets, in which one of the two spin channels is metallic, while the other has an energy gap around the Fermi energy, have attracted increasing research interest because of their promising application to spintronics. The ordered spin arrangement of electrons is formed by the exchange correlation of the electrons, which provides the static magnetic moment of this compound.The information carrier of traditional electronic components such as diode and audion, is electronic charge, but the electronic spin is not considered. In recent years, studies on the semiconductor spintronics indicate that the diluted magnetic semiconductors can be used to manage and store information by means of the electronic charge and spin. However, nowadays, the key to semiconductor spintronics is that the efficiency of spin-polarized electrons injected into semiconductors is very low, one needs to find some magnetic materials with high spin-polarization. Half-metallic ferromagnet has a higher Curie temperature and almost 100% spin-polarization. Therefore, it will become the perfect spin injection fountain to semiconductor.In this paper, our purpose is to predict new half-metallic ferromagnets by the computer simulations in two aspects: organic and inorganic ferromagnetics. With the help of the full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT), we investigated the electronic structure and the magnetism of the organic ferromagnet [(CH3)aN]2MGe4Slo (M = Fe, Cd). They belong to tetragonal system, space group I4 (82), the result shows that [(CH₃)₄N]₂MGe₄S₁₀ are half-metallic ferromagnets. Relative inorganic half-metallic ferromagnets, organic half-metallic ferromagnets are easier to be synthesized, processed, and there has been no corresponding work in experimental field. Hence, whether in theoretical aspect or the aspect of experimental synthesis, much attention has been paid to investigate the mechanism behind the half-metallic ferromagnetism and to study its implication in various physical properties.Dilute magnetic semiconductor (DMS) is also called semi-magnetic semiconductors, by means of magnetic transition metal atoms or ions of rare earth magnetic, alternative non-magnetic cation that formed a kind of magnetic semiconductors material. Under doping different transition metals and different proportion of doping, it shows the different magnetic properties, for example, paramagnetic, anti-ferromagnetic, ferromagnetic and so on. The calculations of the electronic structure and the magnetism of the transition metal Mn- doped semiconductor GaAs(110) orientation indicate that GaAsMn-α, GaAsMn-β, GaAsMn-γare the half-metallic ferromagnets. The spin magnetic moment per molecule originates from the Mn d-d orbit exchange and As p-Mn d orbit hybridization.