基于原子力显微技术的多铁纳米材料力电磁多场耦合性能表征

Multiferroic materials possess multiple ferroic orders simultaneously, rendering them interesting multi-physics couplings，which makes the multiferroic materials promising for a wide range of applications in multifunctional nanodevice. The state of art characterization techniques for magnetoelectric coupling, however, are limited to bulk multiferroic materials, and it is also very difficult to accurately characterize the multi-physics couplings at nanoscale. Motivated by these difficulties, we seek to develop novel scaning probe microscopy based techniques,including piezomagnetic force microscopy (PmFM) and magnetoelectric force microscopy (MeFM), to enable nanoscale characterization of multiferroic materials. Using these newly developed techniques in combination with conventional piezoresponse force microscopy (PFM) and magnetic force microscopy (MFM) that are well established, we will investigate the ferroelectric and magnetic domains of multiferroic materials, as well as their evolution under external mechanical,electric and magnetic fields. Special attention will be paid on the magneto-electro-mechanical couplings at the interfaces between ferroelectric and ferromagnetic phases, so that deep understanding on magnetoelectric coupling in multiferroic nanocomposites can be obtained, making it possible to guide experimental development and analysis of multiferroic materials with superior magnetoelectric coupling.

由于多重有序共存，多铁材料蕴含着非常丰富的力电磁多场耦合效应，在多功能纳米电子器件中具有广阔的应用前景。然而，当前表征多铁材料磁电耦合性能的实验力学手段，主要适用于宏观的块体材料，而且在定量表征方面存在明显的不足，无法对低维多铁纳米复合材料的力电磁耦合作用进行有效的测量。因此本项目的研究目标，在于发展新型的压磁模式和磁电模式的原子力显微技术，并结合传统的压电模式和静磁模式等成熟的原子力显微技术，实现多铁材料纳米尺度力电磁多场耦合效应的原位表征，为低维及纳米结构的多铁材料研究提供强有力的实验力学工具。运用这一系列的原子力显微技术，我们将对低维多铁纳米复合材料及结构的力电磁多场耦合性能进行系统地研究。我们将着重关注力电磁等各种外场作用下的电畴磁畴结构及其演化和翻转，深入探讨多铁材料两相界面处的力电磁相互作用，从而深刻理解其磁电耦合机制，为多铁纳米材料的开发和应用提供指导。

多铁纳米材料制作的传感器、驱动器和多态存储器，可以实现器件的微型化、多功能和低功耗等特色，具有广泛的应用前景。发展纳米尺度表征多铁材料性能的方法能促进多铁纳米器件的研发。本项目中实验方面我们制备了BaTiO3/Fe3O4异质结、GaFeO3薄膜和CoFe2O4-BiFeO3芯壳纳米纤维等一系列不同成分和结构的多铁纳米材料，并基于原子力显微技术，发展了压磁原子力显微技术（PmFM）和新的线圈感应压电力显微技术（PFM）表征方法，采用PFM和可变磁场模式（VFM）组合的原子力显微技术，表征了多铁复合材料纳米尺度的磁电耦合性能。理论方面采用Hankel积分变换方法和等效点电荷模型，建立了一套分析PFM响应的力电全耦合方法，对PFM技术进行了定量分析，研究了畴壁厚度对材料压电响应的影响。相关研究工作已在Acta Materialia、Journal of Applied Physics、Applied Physics Letters、Journal of Materials Researchs等期刊发表SCI论文9篇,EI论文1篇。