多铁性材料异质结和原型器件的设计、制备及性能调控研究

The project is aimed to design and fabricate novel multiferroic materials related thin films, heterostructures and prototype devices, in which there are complex interactions and competitions among charge, spin, orbit and lattice degrees of freedom. Based on our advantages in multi-disciplinary linkage and close connection between theory and experiment, we are able to study many crucial problems related to the electromagnetic properties of multiferroic materials, so as to understand their essential physics, manipulation laws and build next generation of prototype devices. These investigations not only have important scientific significances but also are the fundamentals of the research and development for the new generation of information and energy technologies. The key problems in these researches are:. 1) Exploration and characterization of new multiferroic materials: especially explore layered multiferroics with different ordered phases; systematically investigate the key factors affecting the magnetoelectric coupling effect through various electrical and magnetic measurements and microstructural analysis; and establish the composition-structure-performance relationship.. 2) Growth of the multiferroicity related thin films and heterostructures: explore the preparation technology and growth mechanism of the epitaxial thin films and heterostructures; concern the effects of dopant concentration, atmosphere, microstructure, strain, lattice mismatch and interface state on the growth of thin films; study the important roles of the spin, orbit and charge orders on the physical properties; and achieve the controllable preparation of functional thin films and heterostructures.. 3) Designs, preparations and relevant physical effects of multiferroicity related prototype devices, including resistance switching and tunnel junction based multi-state memory devices; manipulate various magnetoelectric coupling effects of the devices through electric, magnetic, and light fields, etc..We hope to achieve breakthroughs in designing and synthesizing new materials, and building new prototype devices, etc.

设计与制备多铁性量子功能材料薄膜异质结，研究其各种序参量之间的耦合及竞争机制，从中发现新的量子现象、规律和调控方法，并由此发展多铁性相关的原型器件，有重要的科学意义和应用前景。为此，我们将主要开展如下研究：. 1）新型多铁性材料的探索及性能表征：重点探索不同有序相共存的层状结构多铁性新材料，并通过各种电磁性能测量和微结构分析，系统地研究影响材料磁电耦合效应的关键因素，建立材料的成分－结构－性能关系。. 2）多铁性相关的薄膜和异质结制备：探索外延薄膜的生长技术、工艺和机理，关注掺杂浓度、气氛、微结构、应力、晶格失配及界面态等对薄膜生长的影响，探讨自旋、轨道及电荷有序化的重要作用，实现薄膜和异质结的可控制备。. 3）原型器件设计及相关物理效应研究：设计并构建多铁性相关的阻变器件和隧道结等原型器件，通过电场、磁场、光场等实现对器件的综合调控，探索其中与磁电耦合关联的多种效应。

本项目的核心目标是研发多铁性异质结及其信息存储原型器件。主要开展：设计与制备多铁性量子功能异质结，调控各种序参量之间的耦合及竞争，构建多铁性异质结信息存储原型器件。项目执行期内，完成了研究计划，达到了预期目标。主要进展如下：.1、多铁性异质结制备及磁电耦合：1）制备出La0.7Sr0.3MnO3 (LSMO)/BaTiO3/LSMO、LSMO/BiFeO3/LSMO等多铁隧道结，发现了非对称界面离子和电荷的重构现象。2）构建了磁性/PMN-PT薄膜异质结，揭示出铁电场效应对磁性半导体薄膜磁性的影响。3）构筑了多铁性BiFeO3纳米异质结阵列并实现高开关比阻变效应。.2、多铁性信息存储原型器件：1）实现了超快(6 ns)、超低写入电流密度(3x10^3 A/cm^2)、多阻态且具有良好保持和重复特性的非易失多铁性隧道结信息存原型储器；设计了Au/YIG/n-Si异质结构，获得了具有高电阻开关比(~ 10^4)、超快(~ 540 ps)和多阻态的存储器原型。2）构建了磁电耦合异质结忆阻器并实现了塑性特征可调的人工突触模拟。3）构建了自旋阀(Co/Cu/Ni)/PMN-PT多铁电子学存储器原型，实现了纯电场调控的自旋阀多态阻变效应。.3、新材料探索：1）发现了层状结构Bi4NdTi3Fe1-xCoxO15体系的多铁性特征。2）合成了Bi4.2K0.8Fe2O9+δ纳米带，发现了其向一维BiFeO3纳米链的转化规律。3）预测了YMnO3材料的磁电耦合效应，发现反铁磁结构对电极化行为的影响规律；模拟研究了Tm掺杂GdMnO3体系的多铁性行为和Al掺杂CuCrO2体系的多铁相竞争。.在项目的资助下，共发表SCI学术论文101篇，包括Appl. Phys. Rev., Adv. Mater., Adv. Funct. Mater., ACS Nano, ACS Appl. Mater. Interf., Phys. Rev. Lett.等，论文得到国际上的广泛关注。申请发明专利8项，已授权2项。国际会议邀请报告5次，国内会议邀请报告13次。联合举办了4次中国材料大会多铁性材料分会。.在人才培养方面，1人获得国家优秀青年基金资助，3位副教授晋升为正教授。培养毕业博士生10名，毕业硕士生10名，有4人获“国家研究生”奖，2人获“朱李月华”奖。此外，在实验室建设方面也取得一定的进展。

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