Fe3O4/BiFeO3多铁隧道结的电场调控及磁电耦合效应研究

BiFeO3 is a lead-free room-temperature multiferroic material with antiferromagnetic and ferroelectric properties. Therefore it is the best choice for the investigation of room-temperature multiferroics. Note that the use of BFO as the barrier layer has an important role in developing high-performance ferroelectric or multiferroic tunnel junctions. Besides, Fe3O4 is a stable half-metallic oxide with high Curie temperature and the ideal material for spin injection research. The subject of this project is to prepare a series of Fe3O4/BiFeO3 heterostructures and full oxide multiferroic tunneling junctions on single crystal substrates, and mainly focus on the study of electrical and magnetic transport of BFO multiferroic tunneling junctions. The research also includes: the formation mechanism of BFO domain wall under different strain conditions and its influence on the exchange coupling effect of Fe3O4/BiFeO3 heterostructures; the size effect and the influence of the electric field and magnetic field on the anisotropic magnetic properties of multiferroic tunneling junctions; the designing of magnetoelectric devices where the electric field could modulate several important physical properties simultaneously. The intensive study and exploitation of the full oxide multiferroic tunnel junctions composed of half-metal and magnetoelectric multiferroic oxides can provide experimental model as well as theoretical basis for the application of new magnetoelectric coupling devices.

BiFeO3是具有反铁磁性和铁电性的无铅绿色室温多铁材料，是研究室温多铁性能的首选，利用BiFeO3作为势垒层是开发高性能铁电及多铁隧道结的重要环节。Fe3O4是相结构稳定且具有高居里温度的半金属材料，是研究自旋注入的理想材料。本申请课题拟在单晶基底上制备系列Fe3O4/BiFeO3全氧化物异质结及多铁隧道结，重点研究多铁隧道结中的电输运和磁输运；探索不同应变条件下BiFeO3的畴结构及畴壁的形成机理、对Fe3O4/BiFeO3异质结交换耦合效应的影响机制；研究尺寸效应及外加电场和磁场对多铁隧道结各向异性磁电性能的影响；设计实现电场对多个重要物理性质同时进行协同调控的磁电耦合器件。通过对半金属氧化物/磁电多铁氧化物构成的全氧化物多铁隧道结的深入研究与探索，为新型磁电耦合器件的应用提供实验模型及理论基础。

BiFeO3 (BFO)是一种单相多铁材料，具有高铁电居里温度、高反铁磁奈尔温度和高剩余铁电极化强度等优点，可以应用于非易失存储器件。Fe3O4是相结构稳定且具有高居里温度的半金属材料。本工作利用磁控溅射技术制备高质量BFO、Fe3O4薄膜及Fe3O4/BFO异质结构，系统研究其多铁性、磁性与输运特性。利用不同单晶基片，研究了应力下BFO薄膜的界面匹配生长规律，由于高应变类四方相BFO内非对称FeO5五面体诱导的自旋倾斜产生净磁矩，BFO薄膜表现出巨大净磁矩；进一步利用磁控溅射技术制备高质量Fe3O4薄膜，系统研究应变效应下Fe3O4薄膜矫顽场、Verwey相变等特性；构造了Fe3O4/BFO全氧化物异质结，研究了其界面磁电耦合特性；在BFO基异质结中实现了室温电场调控输运特性，解明了电场调控BFO异质结磁电耦合效应的机制。相关结果主要以学术论文形式发表在Appl. Phys. Lett., Adv. Electron Mater., ACS Appl. Mater. Interfaces等学术期刊上。