LiNbO3结构过渡金属氧化物的多铁性的第一性原理研究

Multiferroics represent an attractive class of compounds which combine rich and fascinating fundamental physics with a technologically appealing potential for applications. However, relatively few multiferroics have been identified, and in those that are known, the underlying mechanism is often controversial. In this work, by means of first-principles calculations within the GGA, GGA+U, and HSE functionals, we will investigate the multiferroic behavior in the known transition-metal oxides with the LiNbO3-type structure. The aim of our work is to search the multiferroic compounds with possibly high ferroelectric polarization and strong coupling between magnetism and ferroelectricity. Meanwhile, we will explore the mechanism driving the ferroelectricity and characterize the magnetic properties in those systems. Additionally, considering the fact that transition-metal oxides with a polar structure would be potential multiferroic candidates, we will attempt to theoretically predict new multiferroic materials by substituting transition-metal ions for the A (or B)-site atoms in ABO3-type ferroelectrics with the R3c symmetry. We hope that our results will not only expand our understanding on the multiferroic properties, but also provide a new avenue for synthesizing and designing novel multifunctional materials.

多铁材料具有重要的科学研究和技术应用价值。然而，至今被发现的多铁材料的数量仍十分有限，并且它们的物理机制还不是很清晰。本课题利用第一性原理不同近似方法（GGA、GGA+U、HSE杂化泛函）研究具有LiNbO3结构的过渡金属氧化物的多铁性，找寻具有更高铁电极化值和强磁电耦合的体系，同时探讨它们的铁电驱动机制和磁电耦合机制。此外，通过以过渡金属元素替代LiNbO3结构的ABO3构型铁电体中A位或者B位离子，从而实现极化结构和磁性离子相结合的潜在多铁体系，并理论预测它们的相稳定性和多铁性，同时为实验合成和新功能材料的设计提供理论依据。

多铁材料是一种重要的磁电耦合材料，鉴于其潜在的应用前景和丰富的物理内涵，本课题基于密度泛函理论的第一性原理计算方法，展开了对LiNbO3结构过渡金属氧化物的多铁性的理论研究。我们已经完成对LiNbO3结构过渡金属氧化物MnSnO3和MnTiO3体系的晶体结构、电子/磁结构和铁电性质的研究，理论预测了MnSnO3和MnTiO3体系是一种潜在的多铁材料。研究了双钙钛矿结构Sr2FeOsO6和La2NiCrO6体系的结构、磁电性能，理论解释其磁耦合作用机理。探讨了压力对Sr3Fe2O5结构、电子和磁性的影响，以及四配位FeO4准二维结构对体系电子性质和磁结构的影响。研究类钙钛矿型结构K4Fe3F12体系中电荷有序以及磁电耦合行为。此外，通过与实验课题组的合作，研究SrTiO3体系电子性质，首次在理论上证明立方钙钛矿SrTiO3体系中可以形成极化子。在项目执行的三年时间内，我们已在国际著名物理和化学期刊发表SCI收录学术论文9篇。这些研究工作将为优化和改善现有材料性能及新材料设计提供理论依据和指导。