纳米晶多铁性材料中子衍射研究

Multiferroic materials, in which more than one primary ferroic order parameters (ferromagnetism, ferroelectricity, ferroelasticity) coexist, which have received much attention due to their potential applications in information storage, spintronic devices and magnetic sensor et al. Neutron diffraction can precisely determine the atom positions of light elements and magnetic structure, which has become the most important technique for multiferroic material research. The goal of this project is to optimize the multiferroic properties of BiFeO3 by changing the composition at Bi and Fe sites and the size of nanocrystalline powders. Combining X-ray and neutron powder diffraction, the variation of microscopic structures and electric-magnetic properties with nanocrystallize size, chemical element, temperature, pressure, magnetic field will be investigated. The targets of this project are (i) to provide new ideas for the relationship between microscopic structures and multiferroic properties; (ii) to elucidate the mechanism of the magnetoelectric coupling. This research will have great significance for the development of multiferroic materials.

多铁材料是指同时具备两种或两种以上初级铁性体（铁电性、磁性和铁弹性）特征的材料，在信息储存、自旋电子器件、磁传感器等领域具有广阔的应用前景。中子衍射技术可以准确测定轻元素的原子位置以及微观磁结构信息，已成为研究多铁材料不可或缺的重要技术手段。本项目拟以BiFeO3多铁性材料为研究对象，通过改变Bi和Fe位化学组分，制备系列不同尺寸的纳米晶粉体，从微观结构上调制其螺旋磁性和铁电性。结合中子及X射线粉末衍射等研究手段，系统研究材料微观结构（晶体结构和磁结构）与基本电磁性随晶粒尺寸、化学成分、温度、磁场和压力的演化规律，拓展多铁材料微观结构与物性之间关系的认识，揭示磁电耦合的产生机制，促进多铁材料的发展。

本项目制备了Bi0.9Pr0.1Fe1-xCoxO3、Bi(Fe1-xMnx)O3-BaTiO3等系列样品，通过改变样品制备方法、Bi/Fe位化学组分和烧结温度，制备一系列不同尺寸的纳米晶样品，系统研究了材料微观结构、基本电磁性随晶粒尺寸、化学成分的变化规律。对于Bi0.9Pr0.1Fe1-xCoxO3，在低掺杂区域x≤0.1时，样品的剩余磁化强度随着Co元素掺杂量的增大明显增强，样品Bi0.9Pr0.1Fe0.9Co0.1O3的剩余磁化强度最大，可达0.39 emu/g。在 x>0.1的高掺杂区域样品的磁性开始随着掺杂浓度的进一步增大而减弱。烧结温度升高导致Bi0.9Pr0.1Fe0.9Co0.1O3颗粒尺寸增加，饱和磁化强度减小。