First-Principle Study On The Electronic Structure And Spin Structure Of The Magnetic Materials

With the development of computer, the computation of electronic structure for practical materials (up to one hundred atoms) has become available. On the other hand, density function theory gives a firmly theoretical foundation for the study of ground states of materials, so the first principle calculation based on density function theory has become one of the most powerful tools in condensed matters. With the first principle calculation, we can not only get the ground state properties of material, but also simulate their behaviors under different conditions. This means that we can predict the properties of materials or design the required materials.Here we use the first principle calculation based on density function theory to study the electronic structures of several magnetic materials. Our work can be divided into two parts: one is about the electronic structure and magnetism of FeS₄Sb₂; the other one is about the calculations of the electronic structure and magnetism of the transition metal Mn- doped diluted semiconductor GaAs' supercell. The calculations have been done with the WIEN2K code. It adopts the full-potential linear augmented plane wave method, which is among the most accurate methods for performing electronic structure calculations for crystals.In this paper, with the help of the full potential linear augmented plane wave (FP-LAPW) method based on the density function theory (DFT), we investigated the electronic structure and the magnetism of the ferromagnetic FeSa₄Sb₂. It belongs to space group Pnma (62)。The result shows that at T=295K, the material is the half-metallic ferromagnetism while at T=370K, the material is the metallic ferromagnetism.Dilute magnet semiconductor (DMS) is also called semi-magnetic semiconductor, which is formed by replacing the non-magnetic cations with the magnetic transition metal atoms or rare earth metallic ions. Under doping different transition metals or doping one kind of transition metal with different proportion, DMS shows that the different magnetic properties. In this thesis, we investigate the total local moments and the electronic properties of the ferromagnetic Ga_1-XMn_XAs(X=0.125, 0.5, 0.875). The space group of the Ga_1-XMn_XAs are P(1). And the result shows that the physical properties of the Ga_1-XMn_XAs have great changes with the concentration of the transition metal Mn- doped.