基于巴克豪森噪声与涡流显微镜的磁性薄膜残余应力无损检测方法

Magnetic thin film materials play a key role in the fabrication of advanced magneto-optical recording devices, magnetic field sensors and microwave devices. Residual stress can change the localized magnetic parameters of the film and even induce new easy magnetization axis to result in deterioration of the magnetic properties of the thin films. In addition, the residual stress may lead to lamination between the thin film and its adjacent layers to cause device failure. In this proposal, a novel residual stress measurement method based on magnetic Barkhausen noise and eddy current microscopy is proposed. The homogeneity in magnetic properties will be measured for evaluating the residual stress distribution in the thin film. The main research contents include: (1) Establishment of dynamic hysteresis model and Barkhausen noise model, in which the stress, grain size and film thickness, etc. are involved. Based on the theoretical prediction results, new methods of characterizing residual stress using multiple magnetic parameters will be proposed. (2) Research on special technologies for the excitation, control and precise measurement of the localized dynamic magnetic field. Barkhausen noise and eddy current microscopy with high lateral resolution will be constructed to help investigate the dependency of the localized magnetic parameters (such as the amplitude of Barkhausen noise, eddy current impedance and incremental permeability) on the residual stress. (3) Development of method for residual stress inversion based on theoretical model and model for quantitative prediction of residual stress using intelligent algorithm. Finally, the imaging of distribution of residual stress in the magnetic thin film can be realized. The outcomes of the above research will provide technical supports and solutions for the characterization and process optimization of magnetic thin film.

磁性薄膜是先进磁光存储、磁场测量和微波器件制备中的重要材料。残余应力可以改变薄膜的局域化磁参量甚至诱发新的易磁化轴，大幅降低薄膜磁性能；也可能导致薄膜与相邻层间出现分层，引发器件失效。本项目提出一种基于巴克豪森噪声与涡流显微镜的残余应力磁检测新方法，利用薄膜磁均匀性检测结果评价残余应力分布，主要研究内容包括：（1）建立考虑薄膜应力、晶粒尺寸、厚度等因素的动态磁滞和巴克豪森噪声理论模型，提出残余应力的多种磁参量表征新方法；（2）研究局域化动态磁场的激励、控制和高精度测量技术，研制具有高空间分辨率的巴克豪森噪声与涡流显微镜，实验探究局域化磁参量（巴克豪森噪声幅值、涡流阻抗和增量磁导率等）与残余应力的关系；（3）发展残余应力的理论模型反演和智能定量预测方法，实现薄膜残余应力分布的扫查成像。通过上述研究，为磁性薄膜表征和工艺优化提供技术支持和解决方案。

磁性薄膜是先进磁光存储、磁场测量和微波器件制备中的重要材料，残余应力测试是磁性薄膜制备工艺优化及质量评价的重要内容。本项目研究利用磁巴克豪森噪声和增量涡流方法实现磁性薄膜均匀性无损评价及应力定量检测，在检测理论、高分辨率磁传感器方面取得了有益进展，集成开发了一套磁巴克豪森噪声与涡流显微镜系统，开展了典型实验充分验证了所提出方法和研发系统的有效性。主要进展包括：.（1）建立了含厚度、应力和晶粒尺寸等特性参数的薄膜磁滞方程，推导得到了薄膜磁巴克豪森噪声时域波形理论模型，揭示了薄膜特性参数对磁巴克豪森噪声幅值包络特征的影响规律；引入双高斯函数描述材料和系统对磁巴克豪森噪声频谱的双重滤波效应，得到了改进的磁巴克豪森噪声幅值谱模型，应用改进模型对沿深度方向的应力分布进行定量反演，精度比传统模型得到显著提升。.（2）建立了考虑磁芯几何结构、磁/电特性参数的磁传感器理论模型，定量分析了关键参数对传感器幅频特性的影响规律，指导高空间分辨率磁传感器结构优化设计；构建了磁传感器加工线，基于磁芯末端双侧研磨工艺成功制备出一批次磁传感器，第三方测试结果表明传感器的横向分辨率可达100μm×100μm。.（3）集成四轴运动平台、微型力加载装置及高分辨率磁检测模块，开发了磁检测主控程序、信号处理算法，构建了一套磁巴克豪森噪声与增量涡流显微镜系统；实验测试了传感器提离距离、励磁参数等因素对磁巴克豪森噪声和增量涡流检测信号的影响规律，重复性测试结果表明系统具有良好的稳定性。.（4）利用研制的系统对磁性薄膜材料开展了典型实验测试，提出了组合磁巴克豪森噪声和切向磁场强度的特征参量，实现镍膜厚度和拉应变的定量检测方法；构建了增量涡流特征参量和镍薄膜厚度、应变的关系曲面，实现了不同厚度镍薄膜中拉应变的高精度检测；利用磁巴克豪森噪声扫查方法，实现了材料表面残余应力均匀性成像及定量无损检测。