Spinel Ferrite:First-principles Study

The magnetic material has a wide range of applications. The spinel ferrite as an important class of magnetic materials, its unique electronic structure showing a strong association effect, has rich magnetic and electronic effects, such as Verwey phase transition, magnetoelectric effect and so on. Therefore, we use first-principles calculations and the generalized gradient approximation (GGA)+Hubbard U method to study the electronic structure of the spinel series, magnetic and electrical properties, and their associated physical mechanisms.The content and conclusions of the paper include the following aspects:1. The first chapter describes the historical background of the spinel magnetic materials, and its application.2. The second chapter describes the theoretical calculation method:The first-principles, GGA+U.3. The chapter III specifically addressed a variety of properties for magnetite (Fe3O4), including the situations:The Cubic structure at room temperature and the monoclinic structure at low temperature. The cube structure mainly include:inequality of octahedral(B-bit)site, half-metallic and magnetic anisotropy mechanism; The monoclinic structure mainly includes:the Verwey phase transition mechanism, charge and orbital ordering mechanism. Meanwhile, we also explore muiltiferrite properties of Fe3O4, and the related heterostructure for Fe3O4and other ferroelectric materials.4. The chapter IV specifically addressed the crystal structure of common spinel materials, and the electronic structure of magnetic and electrical properties for FeA (CoxFe1-x) BO4(X=0.00,0.25,0.50,0.75,1.00). We found in this section:different doping dose and doping position not only have an important impact on physical and chemical properties Fe3O4,but also the magnetic moment of the Co atoms also has been changed; When the doping dose is greater than a certain value, the semi-metallic state of CoFe2O4will change into the insulator. 5. The chapter V describes the electronic structure, magnetic and electrical properties of (Zn/Mn/Mg)xCo1-xFe2O4(X=0.00,0.25,0.50,0.75,1.00). We found in this section:the exchange interaction will change between the atoms with the doping dose, and thereby change the magnetic moment of the Co atoms. We also prove:when the doping dose is greater than a certain value, the semi-metallic structure will be transformed into an insulator.6. The chapter VI summarizes the results of this paper, and sent to the outlook.