同步辐射时间分辨的光电子显微磁成像技术和磁涡旋磁化状态控制的研究

It is well known that there is a vortex state in thin, soft ferromagnetic dot of submicrometer size. The vortex state can be characterized by two topological quantities: polarity, which is the up or down direction of the vortex core magnetization; chirality, which is the rotation direction of the in-plane magnetic moment, could be either clockwise (CW) or counterclockwise (CCW). Both of polarity and chirality can be used as a carrier of information. Magnetic nanometer array is the most promising high density magnetic storage medium and logic device on account of the advantage of high heat stability and high signal-to-noise ratio. To realize the application of the magnetic nanometer array in spintronics device, it is important for the independent control of both vortex chirality and polarity. . The time-resolved x-ray magnetic circular dichroism–photoelectron emission microscopy system is a powerful tool to research the reversal mechanism of the magnetic vortex. With this project, construction and development of a time-resolved x-ray magnetic circular dichroism–photoelectron emission microscopy system will be carried out. Time-resolved x-ray magnetic imaging technology has many advantages, such as element specification, nanometer space resolution, and the capability to investigate dynamical properties in electron or spin transport, spin motion, magnetization reversal, and so on. With these advantages, the research on the reversal mechanism and dynamics process of magnetic vortex can be carried out, which have the important significance to the independent control of both vortex chirality and polarity.

磁涡旋是纳米尺度的磁性结构存在的一种特殊的磁畴结构，它的两个参数手征性和极性均可作为信息的载体，而它高的热稳定性和信噪比使其在高密度磁存储和逻辑器件中有着广泛的应用前景。有效控制磁涡旋的手征性和极性是实现其在自旋电子器件方面应用的关键。. 具有时间分辨的同步辐射光电子显微磁成像技术（简称PEEM）是研究磁涡旋动力学和翻转机制，从而实现对其手征性和极性的有效控制的重要研究手段。基于用户需求和国内外的发展趋势，本项目将发展具有时间分辨的PEEM磁成像技术，为广大用户提供一个具备元素分辨能力的磁结构分析和磁成像的超快动力学研究平台。同时，基于建立的时间分辨PEEM平台，面向高密度的磁存储和逻辑器件，开展磁涡旋手征性和极性双重调控的研究，提出快速、低能耗地同时控制手征性和极性的方案，为实现磁涡旋在高密度磁存储和逻辑器件方面的应用奠定良好的理论和实验基础。

磁涡旋是纳米尺度的磁性结构存在的一种特殊的磁畴结构，它的两个参数手征性和极性均可作为信息的载体，而它高的热稳定性和信噪比使其在高密度磁存储和逻辑器件中有着广泛的应用前景，有效控制磁涡旋的手征性和极性是实现其在自旋电子器件方面应用的关键。而具有时间分辨的同步辐射磁动力学研究平台是研究磁涡旋调控机制和磁动力学过程的重要研究手段。基于用户需求和国内外的发展趋势，本项目基于上海光源结合pump-probe和XMCD/XMLD技术发展了具有时间分辨的磁动力学研究平台，为广大用户提供一个具备元素分辨能力和20皮秒时间分辨能力的超快磁结构动力学研究平台。项目面向高密度的磁存储和逻辑器件，开展了磁涡旋手征性和极性双重调控的研究，在具有D2h对称性的磁纳米结构可以通过外加磁场实现对涡旋手征性和极性的双重调控；利用脉冲磁场可以实现涡旋极性2ns的快速可控翻转，脉冲磁场幅度仅需要20~30 mT，提出了快速、低能耗地极性可控翻转的方案；发现利用铁磁和反铁磁双层薄膜纳米结构中交换偏置场也可以实现对涡旋手征性的控制，为实现磁涡旋在高密度磁存储和逻辑器件方面的应用奠定良好了的理论和实验基础。