低维层状多铁性材料的构建与物性研究

Multiferroic material is one of the new quantum material systems with the richest physical connotations, and has important implications for both the fundamental study of condensed matter physics and exploitation of new functional device applications. It is anticipated that multiferroics can be used in information storage, energy transfer, high-precision magnetoelectric sensing and other fields, and it is notable that exploring novel layered multiferroics is becoming a new hot issue for the multiferroic material research. In this project, the process investigations and property researches of low-dimensional layered multiferroic materials will be launched, and a particular attention will be given to the exploration of new materials and novel effects. The main researches include: 1) design and fabricate new type low-dimensional layered magnetoelectric materials, effectively control the composition, crystal structure as well as microstructure of the materials via analyzing the growth mechanism of crystals and controlling the preparation process; 2) make systematically characterizations of the magnetic and electric properties of the low-dimensional layered multiferroic materials, confirm the internal relationship between the layered structure feature and the magnetoelectric coupling effect, then establish the related phase diagram of "growth condition?crystal structure?magnetic/electric property", and further select the best performance material among the material system studied; 3) through various advanced measurement and analysis methods, in-depth understand the interactions and impacts between the surface/interface effect and the magnetoelectric coupling effect in low-dimensional layered multiferroics, sequentially exploit the structural advances of the layered magnetoelectric materials, and design prototype functional devices.

多铁性材料是有着最为丰富物理内涵的新型量子材料体系之一，在凝聚态基础物理研究和新型功能器件开发方面都有深远的意义，预计会在信息存储、能量转换、高精度磁电传感等领域获得应用，而探索新型层状多铁性材料则是多铁性材料研究的一个新兴热点。本项目拟开展低维层状多铁性材料的构建与物性研究，尤其关注新材料与新效应的探索。主要研究内容包括：1）设计并制备新型低维层状磁电材料，通过分析晶体生长机理、改变制备工艺，对材料的成分、晶体结构、微结构等进行有效地调控；2）系统地表征低维层状材料磁电特性，探明层状结构特征和磁电耦合效应的内在关联，建立相应的"生长条件?晶体结构?磁电特性"相图，并进一步筛选得到所研究体系中性能最优的层状多铁性材料；3）通过多种现代测量分析手段，深层次地认识多铁性低维层状材料中的表/界面效应和磁电耦合效应之间的相互作用和影响，从而发掘层状磁电材料的结构优势，设计原型功能器件。

通过对新型低维层状多铁材料材料的探索，能够获得居里温度较高和磁电耦合更强的相关器件。本项目通过水热法、固相反应法、磁控溅射、脉冲激光沉积和分子束外延等多种技术手段，开发生长包括新型低维层状多铁纳米结构、薄膜及复合多层薄膜等多种材料，对它们的结构、微结构和磁电基本性质进行全方位的深入的表征，并探索其中的结构与磁电性能之间的内在联系，取得以下成果：（1）利用水热法合成新室温多铁材料Bi4.2K0.8Fe2O9+δ，通过对其生长机理的研究，可以对该材料的纳米结构的形貌进行细致调控进而改变其磁学特性；更有趣的是，我们还发现Bi4.2K0.8Fe2O9+δ纳米带在真空环境下经过热处可以转化为纯相的一维的BiFeO3纳米链；（2）利用传统的固相反应法制备出层状共生结构Bi4NdTi3Fe1-xCoxO15 - Bi3NdTi2Fe1-xCoxO12-δ，获得了系列样品在室温下的多铁性和磁电耦合效应，探明其中Co含量对其微结构和磁电效应的重要影响；（3）利用磁控溅射生长BiFeO3/La0.625Ca0.375MnO3多铁异质结，探明磁性电极对异质结物性的影响；（4）使用脉冲激光沉积等镀膜技术生长得到La0.6Sr0.4MnO3/BiFeO3/La0.6Sr0.4MnO3、La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3等铁磁/铁电（多铁）/铁磁三明治薄膜结构，利用微纳加工技术制备出多铁隧道结结构，并最终实现了具有非易失的四重阻态和各项异性相关的八重阻态等特性；（5）利用分子束外延技术，生长出高质量的新型磁性层状（二维）材料Sn1-xMnxSe2薄膜体系，在其中观察到了室温的弱铁磁性，并且通过对Mn含量的控制，发现可以实现材料结构从二维到三维的调控。.项目执行期间共发表相关SCI检索学术论文11篇（含2篇已接收但尚未正式发表论文），包括Nanoscale 1篇，Applied Physics Letters 1篇，APL Materials 1篇，Scientific Reports 1篇，Physical Review B 1篇，CrystEngComm 1篇，IEEE Transactions on Magnetics 1篇，Advanced Electronic Materials 1篇，Journal of Applied Physics 3篇。