低维有机多铁材料的相变及磁电耦合机理研究

项目名称： 低维有机多铁材料的相变及磁电耦合机理研究

项目编号： No.11504078

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 数理科学和化学

项目作者： 王淑玲

作者单位： 河北工程大学

项目金额： 20万元

中文摘要： 多铁材料是具有铁电性、铁磁性和铁弹性等多种铁有序的新型多功能材料，在传感器、信息存储、自旋电子学器件等方面有很大的应用前景，成为凝聚态物理和材料科学的热门课题之一。本项目基于实验上合成的有机电荷转移复合物和有机-金属配合物两种有机多铁材料对铁电相变和磁电耦合机理进行研究。一方面，对于有机电荷转移复合物，考虑晶格、电荷、自旋和轨道等自由度以及它们的耦合作用，分析体系的电荷和自旋分布，并研究外场(如电场、磁场和温度)对体系铁电性和磁性及相变的影响，阐明磁电耦合微观机理。另一方面，对于有机-金属配合物，研究氢键引发铁电序的内禀机制，并探讨磁场(电场)对体系电极化强度(磁化强度)的调控。此外，采用第一性原理方法讨论掺杂或者化学修饰对体系的电子分布和晶格畸变以及磁电耦合强度的影响，为有机多铁材料的设计及其在分子元器件上的应用提供理论指导，促进有机自旋电子学的发展。

中文关键词： 多铁性材料；格林函数理论；铁电相变；有机电荷转移复合物；磁电耦合

英文摘要： Multiferroics, defined for those multifunctional materials in which more than one primary ferroic orders coexist simultaneously, such as ferroelectricity, ferromagnetism, and ferroelasticity. And it has become one of the hottest topics of condensed matter physics and material science due to its huge potential application in novel devices, such as sensors, memories, spintronics devices and so on. Based on the organic multiferroics synthesized experimentally, we propose theoretical quantum models to investigate ferroelectric phase transition and magnetoelectric coupling mechanism for two kinds of organic multiferroics, such as organic charge transfer compounds and organic metal complex，by means of Green’s function theory. On the one hand, for organic charge transfer compounds, we study the distribution of charge and spin, the effect of external fields(such as electronic field, magnetic field and temperature) on their magnetic properties, ferroelectric properties and phase transition, and explain the microscopic mechanism of megnetoelectric coupling, considering the lattice, charge, spin and orbital degrees of freedom and the interaction among them. On the other hand, for organic metal complex, we discuss the mechanism of ferroelectricity induced by hydrogen bonding, and the effect of magnetic field(electronic field) on polarization(magnetization). In addition, we study the influence of doping and chemical modification on the electron distribution and lattice distortion, as well as the strength of magnetoelectric coupling, by means of ab initio calculations. This will provide theoretical guide for the design of organic multiferroics and applications in molecular devices, and promote the development of organic spintronics.

英文关键词： Multiferroics;Green's function theory;Ferroelectric phase transition;Organic charge transfer compounds;Magnetoelectric coupling