铁磁相晶体学结构的非中心对称性的研究

项目名称： 铁磁相晶体学结构的非中心对称性的研究

项目编号： No.51471125

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 一般工业技术

项目作者： 杨森

作者单位： 西安交通大学

项目金额： 85万元

中文摘要： 近年来，随着高精度同步辐射XRD对磁性相变的深入研究，越来越多的磁性材料表明其铁磁相变不仅仅是一个纯磁性相变，亦是一晶体结构的相变；同时又随着铁磁相和铁电相共存的多铁材料的研究进展，铁磁相晶体也开始被认为可能具有非中心对称的晶体结构。基于此，本项目提出对铁磁相的晶体结构是否具有非中心对称性这一晶体学难题进行研究。为此，我们分两步进行了前期基础研究：一是通过同步辐射XRD实验和理论证明铁磁相变涉及晶体结构的变化；二是通过晶体结构精修和磁介电常数的测量初步证明铁磁相晶体具有非中心对称的晶体结构。在此研究基础之上，我们拟从宏观性能、微观结构、理论分析等三个方面对铁磁相晶体学结构的非中心对称性进行深入研究。通过本项目的研究，不仅将从实验上直接证实铁磁相晶体具有非中心对称的晶体结构，同时也从理论上阐释这一具有非中心对称晶体结构的铁磁相的物理起源，为探索和发现具有奇特物理性质的新材料提供一种有效途径。

中文关键词： 晶体结构；非中心对称；铁磁相变；同步辐射X射线衍射；多铁性

英文摘要： Recently, ferromagnetic transitions of more and more magnetic materials are proved to involve not only purely an ordering of magnetic moment, but also a change of crystal structure or symmetry, by using of high-resolution synchrotron x-ray diffractometry (XRD). Furthermore, some ferromagnetic materials are believed to possess the noncentro-symmetrical crystal structures. Therefore, we propose a proposal to systematically study the noncentro-symmetrical crystal structure of ferromagnets. To successfully fulfill this proposal, we have performed some research work in advance. For example, we have proved that the ferromagnetic transition is also a transition of crystal structure, by employing the synchrotron XRD and phenomenological theory. For further detail, we have explored the possibility of noncentro-symmetrical crystal structure of ferromagnets by using method of structure refinement. At the same time, our experimental studies on the magnetodielectric effect indirectly proved this possibility of noncentro-symmetrical crystal structure in ferromagnets. Here, based on our previous results about crystal structure change of ferromagnetic transition, we are willing to study the noncentro-symmetrical crystal structure of ferromagnets from the views of physical property test, microstructure observation and theoretical analysis. Through this study, we look forward to the following three goals. First, we will directly prove that the ferromagnets possess the noncentro-symmetrical crystal structure. Second, we will clarify the underlying physical mechanism of noncentro-symmetrical crystal structure of ferromagnets. Third, we will provide a new way to explore and discover the functional materials with exotic properties.

英文关键词： Crystal structure;Noncentro-symmetry;Ferromagnetic transition;Synchrotron XRD;Multiferroic