交换偏置多铁异质结构中电场调控的非易失性可逆磁矩翻转

Electric-field control of magnetism exhibits promising application prospect in spintronics devices and high-density information storage due to the advantages of low-power consuming, high response speed, and so on. In conventional ferromagnetic/ferroelectric multiferroic heterostructures, the strain-mediated electric-field-controlled magnetism can displays remarkable effect at room temperature. However, in general, the manipulation effect is volatile and needs the assistant of bias magnetic field, besides the magnetization rotates 90° at most. From the viewpoint of practical application in information storage, realizing reversible and non-volatile 180° magnetization reversal by an electric field under zero bias magnetic field is very important and is still an open challenge, which requires novel multiferroic heterostructures design. Aiming at the bottleneck problem, we investigate the FeGa/IrMn/PMN-PT multiferroic heterostructures composed of ferromagnetic/antiferromagnetic/ferroelectric in this project, which combines the electric-field control of exchange bias and specific PMN-PT ferroelectric substrate with non-volatile ferroelastic strain in this structure. Through modification of the ratio and angle between the unidirectional anisotropy induced by interfacial ferromagnetic/antiferromagnetic coupling and the electric-field-induced uniaxial anisotropy, optimizing the interface of films, coercivity, exchange bias field, the orientation and composition of single crystal substrate, ferroelastic domain switching pathway and so on, explore the approaches to realize purely electric-field-manipulated non-volatile and reversible magnetization reversal under zero magnetic field at room temperature. Furthermore, we will clarify the underlying physical mechanism and analyze the general rules of electric-field-controlled magnetization reversal in exchange-biased multiferroic heterostructures. This work can provide the experimental evidence and theoretical guidance for the development of low-power consuming magnetoelectric random access memory.

电场调控磁性因其低能耗、高速度等优势而在自旋电子学、信息存储领域极具应用前景。在常规铁磁/铁电多铁异质结构中，基于应变机制的电控磁在室温下具有显著效应，但其调控一般是易失性的、需要偏置磁场且一般最大驱动磁矩转动90°。从存储应用角度出发，实现无偏置磁场下电场调控的非易失性可逆180°磁矩翻转非常重要，目前仍然存在巨大挑战，需要新的异质结构设计。针对该研究瓶颈，本项目拟在由铁磁/反铁磁/铁电构成的FeGa/IrMn/PMN-PT多铁异质结构中，将电场调控交换偏置与具有非易失性铁弹应变的PMN-PT铁电衬底相结合，通过调节铁磁/反铁磁界面交换耦合产生的单向各向异性与电场诱导的单轴各向异性之间的比例和夹角、矫顽力、交换偏置场、铁弹畴翻转、衬底晶向与组分等因素，探索室温零偏置磁场下实现纯电场调控的非易失性可逆磁矩翻转。并对其中的物理机制和调控规律进行分析，为发展低能耗的磁电随机存储器奠定实验基础。

电场调控磁性因其低能耗、高响应速度等优势而在自旋电子学、信息存储领域极具应用前景。本项目将磁性薄膜生长在PMN-PT压电单晶衬底上，利用电场诱导应变机制对薄膜磁性进行调控。围绕本项目研究内容取得以下研究成果：（1）在不同取向的PMN-PT压电单晶衬底上生长了具有良好交换偏置效应的FeCo/IrMn薄膜，通过对PMN-PT衬底施加原位电场能够增大薄膜交换偏置场和矫顽场；（2）通过磁力显微镜原位研究Co/PMN-PT多铁异质结构中电场驱动的磁畴壁移动，并和宏观磁性以及磁输运性质相结合，揭示磁各向异性状态可以通过电场在面内各向同性与面内单轴各向异性之间可逆转换；（3）利用衬底铁弹应变，在Co/PMN-PT (011)多铁异质结构中实现脉冲电场对磁性的非易失性调控；（4）在单相多铁Y2CoMnO6体系中，利用A位Sr2+离子掺杂调节反位无序度来调控交换偏置效应，并且系统研究了掺杂对该体系结构、磁性等性能的影响。上述研究成果为发展新型低能耗磁电器件提供了实验依据和理论指导。