柔性磁性非晶薄膜中应力对磁各向异性的调控及其机理研究

The currently rapid development of flexible electronic devices requires the flexibility of traditional devices. Magnetic materials are important components to fabricate the electronic devices and the multi-functions of the magnetic device are closely related to their magnetic anisotropy. Therefore, it is very important to study the relationship between the magnetic anisotropy and applied stress/strain in magnetic materials on flexible substrates, and to clarify the microscopic mechanism of the modulation. In this project, the applicant proposes to apply stressduringfilm growth processbased on stress engineering to modulatethe magnetic anisotropy of magnetic materials. The magnetic materials with strain nonsensitivity of easy magnetization axis will be prepared bysolving the controllability of stress-induced and magnetic field-induced magnetic anisotropies. The electronic density and microstructure under different stress will be studied by synchrotron radiation X-ray spectrum, which can be used to clarify microscopic mechanism of magnetoelastic anisotropy. These results will have important significances for the development of flexible magnetic devices.

传统功能器件的柔性化是当前发展柔性电子设备的迫切需求。磁性材料不仅是制备电子器件的重要组成部分，而且其磁各向异性大小和方向与器件的功能特性密切相关。因此，研究柔性衬底上应力/应变对磁性材料的磁各向异性的调控规律，阐明调控的微观机制具有重要的意义。在本项目中，申请人拟基于应力工程在薄膜生长的过程中预加应力来调控磁性薄膜的磁各向异性；通过解决制备过程中磁场和应力诱导的磁各向异性的可控性问题，获得易磁化轴方向对应变不敏感的磁性薄膜的制备方法与工艺；通过同步辐射X射线吸收谱研究不同应力状态下材料的电子态密度和微结构特性，阐明磁性非晶薄膜中磁弹各向异性产生的微观起源。研究结果对研发柔性磁性器件具有重要的指导意义。

磁各向异性是磁性材料的重要内秉参量之一，不仅决定着磁性材料的磁矩取向和矫顽力，也会影响到磁性器件的工作频率乃至功耗。研究如何调控磁各向异性及其调控机理一直是个磁性材料和磁性物理中的核心问题之一。在柔性PVDF衬底上沉积非晶CoFeB薄膜，利用PVDF各向异性热膨胀给薄膜施加应力，通过测各向异性磁阻对于不同应力状态下的磁弹各向异性常数进行了研究。在柔性的PET衬底上通过弯曲和施加磁场制备磁性薄膜，这样可以预先诱导出一个较强的单轴磁各向异性，使得薄膜在随后的弯曲受力过程中，薄膜可以在一定应变范围内能保持在一个方向。利用XMCD测量了不同应力状态下非晶CoFeB薄膜中Co和Fe的轨道磁矩，外加应力导致了轨道磁矩发生变化是产生磁弹各向异性的主要起源。研究结果为进一步理解磁弹各向异性和发展柔性磁电子器件奠定了基础。