外延多铁异质结中磁化翻转路径的电场调控与磁阻检测的研究

Electric field control of magnetization switching in multiferroic materials through inverse magnetoelectric coupling effect lays the foundation for the preparation of magnetoelectric random access memory. Compared with amorphous and polycrystalline ferromagnetic films, epitaxial films with cubic magnetocrystalline anisotropy have four stable in-plane easy magnetization directions, which provides an opportunity for us to understand the physical mechanism and regulation process of magnetization switching. Nevertheless, we can't get the detail magnetization switching routes according to the electric field induced 90° magnetic easy axis switching. To solve the problem, in this project, we will choose epitaxial Fe3Si/PMN-PT heterostructures as the research objects due to its high spin polarization at room temperature. On the basis of systematically analyzing of the regulation of magnetic field and electric field on magnetization reversal path, shape magnetic anisotropy is introduced to overcome the uncertainty of 90° magnetization reversal path in epitaxial thin films. Then, under zero magnetic field, we will conduct an exploitation on determinate and controllable 90° and 180° magnetization switching by pure electric field. Finally, through measuring magnetic transport properties to recognize the magnetization state, the corresponding relationship of electric field, magnetization and magnetic resistance state will be established. This investigation could provide technology reserves and experimental foundation for the multistate electronic memory devices.

利用多铁材料的逆磁电耦合效应来实现电场对磁化翻转的调控是制备磁电随机存储器的基础。相比于非晶和多晶铁磁薄膜，具有立方磁晶各向异性的外延薄膜在面内存在四个稳定的易磁化方向，这为磁化翻转的机制研究和过程调控提供了契机。但是目前基于磁易轴方向90°翻转的电场调控磁性并不能给出纯电场对磁化翻转路径的调控。针对这一问题，本项目拟以室温下具有高自旋极化率的外延Fe3Si/PMN-PT异质结为研究对象，在系统分析磁场和电场共同调控磁化翻转路径的基础上，引入形状磁各向异性克服外延薄膜中90°磁化翻转路径的不确定性，在零磁场下，探究纯电场对面内确定方向的90°和180°磁化翻转路径的调控；拟通过磁输运方法检测磁化状态，建立外加电场-磁化状态-磁阻之间的对应关系，为多阻态存储器件的设计和应用提供技术储备与实验基础。

磁性材料中磁化状态调控和检测是实现磁信息写入和读取的关键，然而如何实现磁化翻转的表征、调控和检测具有非常重要的意义。本项目基于外延薄膜的面内四重磁各向异性，系统研究衬底温度与Fe75Si25/MgO(001)薄膜结晶性、磁各向异性变化、静态和动态磁性参量之间的关系。在最佳温度下制备了外延Fe75Si25/MgO(001)薄膜，得到了外磁场作用下的磁化翻转过程并观测到实时的磁畴变化。在此基础上制备了相应的Fe75Si25/ (011)PMN-0.3PT、Fe80Si20/ (011)PMN-0.3PT、Fe80Si20/ (011)PMN-0.32PT多铁异质结，在零磁场下得到纯电场对磁化强度和磁畴的调控。掌握了磁场&电场和纯电场独立作用下的磁化翻转路径的内在物理机制。并通过引入形状各向异性，在微磁学模拟中实现了纯电场作用下确定路径的180°磁化翻转。为研究纯电场作用下薄膜磁化翻转过程中磁电阻的变化，搭建了磁电输运测试系统并进行纯脉冲电场下的稳定性测试，可检测电场对磁化翻转的调控效果。本项目的研究工作为新型磁电随机存储器的设计提供依据和实验数据支持。