稀土正铁氧体中奇异磁相变与铁电、磁介电的关联效应研究

项目名称： 稀土正铁氧体中奇异磁相变与铁电、磁介电的关联效应研究

项目编号： No.11274221

项目类型： 面上项目

立项/批准年度： 2013

项目学科： 数理科学和化学

项目作者： 曹世勋

作者单位： 上海大学

项目金额： 82万元

中文摘要： 钙钛矿结构稀土正铁氧体具有丰富而奇异的磁特性，部分稀土正铁氧体被预言是极具前景的磁电材料。针对目前发现的(Dy,Gd)FeO3的磁电耦合效应在极低温这一问题，本课题将从考察磁相变附近的铁电、介电异常开展系统的工作，寻找新的室温附近的多铁性体系。拟选取稀土正铁氧体为研究对象，采用光学浮区法制备高质量单晶样品，以物性测量为主要手段，辅以第一性原理计算，系统深入地研究该体系的磁电性质。研究磁相变在温度和磁场诱导下的行为及其对晶体结构、晶格畸变的依赖性，阐明磁相变与铁电、磁介电异常之间的关联以及对磁电耦合的影响。探讨A位和B位离子掺杂对自旋重取向、负磁化等磁相变及铁电、磁介电的影响，搞清其独特磁结构中稀土与铁离子之间的交换收缩效应。结合变温XRD和拉曼测试，澄清铁电、磁介电与自旋-声子耦合的内在关联。结合理论分析，设计有效掺杂，提高磁相变温区，寻找接近室温的多铁性体系，探索新的磁电耦合机制。

中文关键词： 稀土正铁氧体；磁相变；自旋开关效应；磁电耦合；关联效应

英文摘要： Rare-earth orthoferrites with perovskite structure have unique magnetic properties. Some rare-earth orthoferrites have been predicated to be promising candidates as magnetoelectric materials from the viewpoint of the magnetic symmetry.However,the gigantic magnetoelectric coupling in (Dy,Gd)FeO3 appears at very low temperature. In this project, we will systemly examine the anomalies of ferroelectric and dielectric around exotic magnetic transitions, looking forward to find a new multiferroic system at around room temperature. We will comprehensively study the magnetoelectric properties of rare-earth orthoferrites. The high quality single crystals of orthoferrites are prepared by optical floating zone technique and the properties are mainly measured by the physical properties measurement system. The first-principle calculation will be also developed to assist the understanding the properties.The behavior of magnetic transition induecd by the applied magnetic field and temperature, the dependence of magnetic transition on the crystal structure and distortion, and the relevance of ferroelectricity and magnetodielectric effect with magnetic transition will be comprehensively carried out.In addition, the substitution effect of A site and B site on the magnetic transition, ferroelectricity, and magnetodielectric effec

英文关键词： rare earth orthoferrites；magnetic phase transition；spin switching effect；magnetoelectric coupling；correlation effectg