新型电子铁电体系LuFe2O4(LuFeO3)n（n＝0, 1, 2）的电荷调制结构和物理性能研究

项目名称： 新型电子铁电体系LuFe2O4(LuFeO3)n（n＝0, 1, 2）的电荷调制结构和物理性能研究

项目编号： No.10874227

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 电工技术

项目作者： 杨槐馨

作者单位： 中国科学院物理研究所

项目金额： 36万元

中文摘要： 本研究项目中，我们主要关注电子铁电体及和电荷序相关的多铁体系的结构和物性。主要研究内容包括：系统研究了电荷阻挫体系(RFe2O4)(RFeO3)n结构和物理性能；分析了氧含量对LuFe2O4-δ65288;n=0）铁电性能和电荷序的影响，在低温下观察到了多重电荷序和电子相分离现象；利用球差校正电镜对氧空位进行了直接观察。合成了系列(RFe2O4)(RFeO3)n掺杂样品，发现在Mn掺杂的Lu2Fe3O7（n=1）中, 电荷序有所改变，漏导现象和铁电性能得到了改善。开展了多铁材料Fe2OBO3中的纳米极化畴及磁电耦合效应研究。利用低温原位电子显微镜技术在Fe2OBO3中观察到了明显的无公度调制结构及其对应的从室温几个纳米到低温数百纳米随温度演变的反相条带状畴结构，结合结构和介电分析推测Fe2OBO3可能是一种新的电荷有序电子型铁电体，而条带状反相畴对应系统的铁电极化畴，并预测Fe2OBO3在相变点存在磁电耦合效应。实验证实了在相变点附近外电场可以改变材料的磁化状态，而相变点的磁电耦合效应最为强烈，在5kV/cm的外场下，δ#21487;达33%。

中文关键词： 电子铁电体；电荷有序；多铁性；结构相变；透射电镜

英文摘要： In this project, our work focus on the microstructure and physical property correlation in electronic ferroelectric compounds and other multiferroic materials related with charge ordering. Structural and physical properties of charge/spin frustrated (RFe2O4)(RFeO3)n system have been systematically investigated. The notable oxygen-deficient effect on charge ordering and ferroelectric properties have been analyzed in LuFe2O4-δ=0) materials; Multi-mode charge ordered states and electronic phase separation have been observed at low temperature. Our study also reveals that Mn substitution for Fe in Lu2Fe3O7(n=1) can notably suppress the conducting leakage current and results in clear hysteresis loops in the polarization-electric field switching curves. Polar nanodomains and magnetoelectric effect in multi-ferroic Fe2OBO3 have been systematically investigated. In-situ TEM investigations demonstrate that the charge ordering (CO) transition in Fe2OBO3 can be well characterized by a temperature-dependent incommensurate modulation. The anti-phase nanodomains in the CO state transform into ferroelectric domains at low temperature. These domains could play a critical role in triggering a high dielectric constant and notable dielectric dispersion. Moreover, measurements of the magnetoelectric coupling show the existence of giant electrically induced changes in magnetization (M≈3% under 5kV/cm) around the magnetic transition.

英文关键词： Electronic ferroelectricity; Charge ordering; Multiferroics; Phase transition; TEM