双钙钛矿结构稀土镍锰氧化物超晶格的多铁性质

发布时间：2018-04-24 09:33

本文选题：多铁 + 双钙钛矿　；参考：《电子科技大学》2016年硕士论文

【摘要】：多铁材料应用前景令人瞩目,已经成为功能材料研究领域的热点。钙钛矿结构氧化物拥有丰富的物理性质特别是潜在的室温多铁特性,这类材料可以用来设计制作四存储态存储器、可调微波器件等多种新型自旋器件,因而有望成为推动信息产业革新的关键力量。当前对钙钛矿结构多铁材料的研究焦点主要集中在寻找铁磁序、高自发极化强度、具有室温以上转变温度的体系。以密度泛函理论为基础的第一性原理具有准确、简便的特点。随着计算速度的不断提升,第一性原理日益成为物理学、化学、生物医药学、材料学等学科领域重要的研究手段。利用第一性原理有助于研究钙钛矿结构材料的多铁特性。本文采用第一性原理计算软件VASP研究双钙钛矿结构的稀土镍锰氧化物有序超晶格的多铁性质。第一,对Pr2NiMnO6/La2NiMnO6有序超晶格结构的多铁性质进行研究。首先按照B位的不同排列方式以及不同的磁序分别计算六种超晶格结构,从中找出了满足产生铁电自发极化条件非金属态的[111]FM序。然后详细分析[111]FM序的基态几何结构,给出其八面体旋转角、A位离子位移等结构信息,分析结构畸变对3d电子态的影响。最后利用现代极化方法的Berry Phase算法计算体系的自发极化。第二,研究Er2NiMnO6/La2NiMnO6有序超晶格结构多铁性质。首先计算体系的结构特征,给出一系列畸变参数。然后结合间接交换作用阐述其结构畸变对体系电子结构特别是磁矩的影响。最后分析结构极化强度的方向以及幅度与A位离子半径的关系。第三,在掌握上述超晶格多铁性质的情况下,尝试调控铁电极化强度。首先,按照A位离子半径不同分别计算若干连续超晶格结构的极化强度,分析极化强度与离子半径的联系。接着,构建间断超晶格结构,引入库伦相互作用,尝试提高体系的极化强度,分析极化强度增大的原因。最后,分析间断超晶格间断处上下两部分的结构特点,阐述上下两部分畸变程度的不同与B位离子排列方式的关系。从结构设计到理论计算与分析,本文得出了一些有益的结论,这些结论可以为以后多铁材料的研究提供参考。
[Abstract]:The application prospect of multi-iron materials has attracted much attention and has become a hot spot in the field of functional materials research. Perovskite oxides have abundant physical properties, especially the potential room temperature polyferric properties. This kind of materials can be used to design and fabricate a variety of novel spin devices, such as four-storage memory, tunable microwave devices, etc. As a result, it is expected to become a key force in promoting innovation in the information industry. At present, the research focus of perovskite multi-iron materials is to find ferromagnetic order, high spontaneous polarization, and have the transition temperature above room temperature. The first principle based on density functional theory is accurate and simple. With the improvement of computing speed, first principles have become an important research tool in physics, chemistry, biomedicine, materials science and so on. The first principle is helpful to study the multi-iron properties of perovskite structure materials. In this paper, the properties of the ordered superlattices of rare earth nickel manganese oxides with double perovskite structure have been studied by the first-principle calculation software VASP. Firstly, the polyferric properties of Pr2NiMnO6/La2NiMnO6 ordered superlattices are studied. At first, six superlattice structures are calculated according to the different arrangement of B sites and different magnetic order, and the [111] FM order which satisfies the condition of generating ferroelectric spontaneous polarization is found out. Then the ground state geometric structure of [111] FM order is analyzed in detail, and the structure information of the octahedron rotation angle A position is given, and the influence of structural distortion on 3D electronic state is analyzed. Finally, the spontaneous polarization of the system is calculated by using the Berry Phase algorithm of the modern polarization method. Secondly, the polyferric properties of Er2NiMnO6/La2NiMnO6 ordered superlattices are studied. First, the structural characteristics of the system are calculated, and a series of distortion parameters are given. Then the influence of the structural distortion on the electronic structure, especially the magnetic moment, of the system is discussed in combination with the indirect exchange action. Finally, the relationship between the direction and amplitude of polarization intensity and the ion radius at site A is analyzed. Thirdly, we try to regulate the intensity of iron electrode under the condition of mastering the properties of the superlattice. Firstly, the polarization intensity of several continuous superlattices is calculated according to the different ion radius at site A, and the relationship between polarization intensity and ion radius is analyzed. Then the discontinuous superlattice structure was constructed and the Coulomb interaction was introduced to try to improve the polarization intensity of the system and analyze the reasons for the increase of the polarization intensity. Finally, the structural characteristics of the upper and lower parts of the discontinuous superlattice are analyzed, and the relationship between the degree of distortion of the upper and lower parts and the arrangement of B site ions is discussed. From structural design to theoretical calculation and analysis, some useful conclusions are obtained in this paper, which can be used as a reference for the study of multi-iron materials in the future.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB34

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