复合势垒层多铁隧道结中磁电耦合机制及界面调控研究

Multiferroic tunneling junction has a good potential application in multi-states memories due to its unique magnetoelectric coupling effect and excellent storage function. Because of low Curie temperatures and/or weak magnetoelectric coupling effect in single-phase multiferroic materials, multiferroic tunneling junction is limited to the application. For this motivation,multiferroic tunneling junction with composite barriers of ferroelectric/ferromagnetic layers will be studied in this proposal. Tunneling junctions with ferroelectric/ferromagnetic barriers will be prepared by using laser molecular beam epitaxy technology and MEMS technology. Energy bands will be designed to match the energy band structures of these interfaces. The effects of the characteristic parameters and converse-piezoelectric effect of the interfaces on the spin transport will be researched. A model will be given to investigate the technique and mechanism of controlling the spin transport.The impacts of electric structure,stress and characteristic parameters of the barriers upon the magnetoelectric coupling will be studied to explore the method and mechanism of strengthening such coupling. The realtions among the stuctures,intefaces properties and storage properties of the junction will be clarified. The functions of low-power electric writing and nondestructive reading of the multiferroic tunneling junction will be gained.The results of this proposal will help us gain an insight into the spin transport and magnetoelectric coupling mechanism of the multiferroic tunneling junctions and give an applicative advice of novel memory devices based on tunneling junctions.

多铁隧道结由于其独特的磁电耦合效应和优异的存储功能，在多态存储器领域有着很好的应用前景。但现有单相多铁材料的居里温度过低或者磁电耦合效应不强，限制了多铁隧道结的应用开发。本项目拟采用激光分子束外延方法，结合表面微加工技术，研制铁电/铁磁复合势垒层的多铁隧道结；应用能带工程设计方法实现多个界面的能带结构匹配设计，研究界面势垒层特征参数及势垒层逆压电效应对电子自旋输运的作用规律，建立多铁隧道结中自旋输运的理论模型，探索自旋输运的调控机理和方法；研究多个界面的电子结构、应力分布以及势垒特征参数对磁电耦合效应的影响，探索磁电耦合增强的技术手段和调控机理；阐明隧道结的微观结构、界面特性与其存储特性的关联，实现多铁隧道结的低功率电写入和非破坏磁读取功能。本项目的研究成果将有助于进一步认识多铁隧道结的自旋输运和磁电耦合机制，对于开发新型隧道结存储器件也具有很好的实际意义。

多铁隧道结具有独特的磁电耦合效应和优异的存储功能，在存储器领域有很好的应用前景。本项目采用激光外延方法，结合表面微加工技术，研制出铁电/铁磁复合势垒层的多铁隧道结；研究了铁电/铁磁薄膜在多种底电极和衬底上的外延生长工艺。分析了不同电极（衬底）与势垒层形成的界面能带结构，界面结构对电势分布特征的影响。研究了势垒层的铁磁性/铁电性、势垒层的逆压电性、势垒宽度及高度等因素对电子输运的作用和影响规律。探索了隧道结中自旋输运的调控手段与调控机理。研究了多个界面的电子结构、应力分布以及势垒层的特征参数对磁电耦合的作用。计算了势垒层的铁电/铁磁性、界面的磁矩分布及电极/基片因素对磁电耦合系数的影响。研究了在外加电场及磁场的作用下，隧道结的TMR及TER效应及其变化规律。分析了多态存储特性的电子输运规律，多态存储特性与外加电场及磁场的关联。运用铁电体的唯象理论和偶极子对交变电场的响应，提出了在电滞回线测量中偶极子的滞后冷冻效应模型，对极化的低温退化现象做了合理解释。理论分析指出，在低温下铁电体的铁电性没有失效。. 在完成本项目中，已发表相关的学术论文10篇，其中SCI收录6篇，EI收录1篇。本项目的研究成果将有助于进一步认识多铁隧道结的电子输运过程和磁电耦合机制，对于开发新型隧道结存储器件也具有很好的理论借鉴意义。