低维多铁材料涡流畴结构相变机理及其力电磁耦合效应研究

Ferromagnetic/Ferroelectric vortex domain structures in low-dimensional multiferroics can exhibit complicated coupling behaviors (i.e., mechanical, electrical, magnetic and thermal, etc.) and novel physical effects, which leads to the features of polymorphism and multi-controllability that are significantly important in both basic research and device applications. However, currently it is still not very clear about the formation, transition, stability and controllability mechanisms of vortex domain structures in low-dimensional multiferroics. More importantly, so far no investigations have been conducted to systematically study the electro-magneto-elastic coupling effects of vortex domain structures in low-dimensional multiferroics and explore their polymorphism and multi-controllability, with the prospects for their applications to be further discovered. In this project, with comprehensively considering the mechanical, electrical and magnetic factors of materials, we will conduct a systematical investigation on vortex domain structures in low-dimensional multiferroics, including the formation, transition, stability and controllability mechanisms, related properties, response behaviors to external fields, and the prediction of potential electro-magneto-elastic coupling effects. The project will combine theoretical modeling, multi-scale and -fields simulation as well as experimental analysis to make an in-depth study on the effects of material composition, ambient temperature, interface, size, applied loads (mechanical, electrical and magnetic loads) and other factors on the properties of vortex domain structures in low-dimensional multiferroics, and to find optimal solutions for applying vortex states in multiferroics, which should lay a research foundation for related device applications.

低维多铁材料磁电涡流畴结构具有复杂的力、电、磁、热耦合行为和奇异物理特性，其多态性和多重可调控性使其在理论基础和器件研发方面均具有重要研究价值。当前，针对低维多铁材料涡流畴结构的形成、相变、稳定及可控性机理仍不清晰，更未见针对低维多铁材料涡流畴结构力-电-磁耦合效应的深入探讨以及探索其多态性和多重可调控性的相关研究报道，其应用前景也待进一步开发。本项目将综合考虑低维多铁材料力、电、磁等诸多要素，系统研究低维多铁材料中磁电涡流畴结构的形成、相变、反转及稳定机理，揭示磁电涡流畴结构相关特性及外场响应行为，预报可能存在的力-电-磁耦合效应机制。本项目更重点结合理论解析、多场跨尺度模拟和实验分析，深入研究材料组分、温度、表面、界面、尺寸及载荷(力、电、磁)等因素对低维多铁材料中磁电涡流畴结构相关特性的影响规律，寻求应用多铁材料磁电涡流态的最优方案，为低维多铁功能器件应用奠定研究基础。

低维多铁材料磁电涡流畴结构具有复杂的力、电、磁、热耦合行为和奇异物理特性，其多态性和多重可调控性使其在理论基础和器件研发方面均具有重要研究价值。项目围绕低维材料磁电涡流畴结构相变机理及其力电磁耦合效应展开了系统、深入的理论和实验研究。理论预报了表面屏蔽和温度对铁电纳米点涡流畴结构稳定性的影响规律，给出涡流畴结构的稳定相图及相变路径；发展了针对铁磁纳米点体系的铁磁相场模型，系统研究了铁磁涡流畴结构的稳定性及单畴-涡流畴相变的力电调控；揭示了非均匀载荷下铁电涡流畴的电学翻转方案及涡流畴结构的力学写入机制；进而对铁电/铁磁涡流畴结构手性翻转难题展开了深入研究，提出了三种针对涡流畴结构手性翻转的力电机制；基于结构设计实现铁电材料呈现极化-涡旋多序态，并发现该态具有高力电耦合特性及在扭力下的可控性；发展了基于LLG模型的微磁学模拟方法及自旋晶格动力学方法，深入揭示了铁磁斯格明子态力电磁耦合效应。实验方面，对铁性纳米材料的实验制备及涡流畴结构表征进行了大量探索，获得高质量的外延单晶PZT和BFO纳米点阵列，并对其中的涡流畴结构和其他畴结构进行了表征分析和调控，针对界面磁性斯格明子的实验研究也在顺利进展中，为下一步实验研究磁电涡流畴结构的力电磁耦合效应奠定了良好的基础。研究成果在力学、物理及材料学术期刊包括JMPS、Acta Mater.、npj Comput. Mater.、ACS AMI、Sci. Rep.、Phys. Chem. Phys. Chem.、Appl. Phys. Lett.、JPCM等国际重要期刊发表SCI论文30余篇，并有一些成果待整理发表中。由于对磁电涡流态力学可控研究贡献，我们获邀在顶级期刊Rep. Prog. Phys.撰写长达87 页综述论文，全面总结了磁电涡流态力学可控性相关研究，并提出诸多力学机理及创新思路。本项目提出了一批低维铁性材料磁电涡流畴结构的力电磁热耦合调控方案，对低维材料磁电涡流畴结构的应用具有重要的指导意义。