Non-volatile multi-state magnetic domain transformation in a Hall balance

High performance of the generation, stabilization and manipulation of magnetic skyrmions prompts the application of topological multilayers in spintronic devices. Skyrmions in synthetic antiferromagnets (SAF) have been considered as a promising alternative to overcome the limitations of ferromagnetic skyrmions, such as the skyrmion Hall effect and stray magnetic field. Here, by using the Lorentz transmission electron microscopy, the interconversion between the single domain, labyrinth domain and skyrmion state can be observed by the combined manipulation of electric current and magnetic field in a Hall balance (a SAF with the core structure of [Co/Pt]₄/NiO/[Co/Pt]₄ showing perpendicular magnetic anisotropy). Furthermore, high-density room temperature skyrmions can be stabilized at zero field while the external stimulus is removed and the skyrmion density is tunable. The generation and manipulation method of skyrmions in Hall balance in this study opens up a promising way to engineer SAF-skyrmion-based memory devices.     

基于迭代反演的非磁性材料复介电常数测量及初值选取方法

复介电常数是反映材料宏观电磁性质的重要参数,电磁领域相关材料和器件的选取、设计及应用都必须基于材料在工作频段的电磁参数.数值迭代法是反演计算材料复介电常数的重要方法,但一直存在难以准确给出迭代初始值的问题.本文基于吸波材料介电常数与反射率的关系,提出了一种迭代法反演吸波材料介电常数的初值选取方法,以此为基础构建了一种利用反射参数反演计算单层吸波材料、多层材料中唯一未知层材料复介电常数的方法,并通过实例测试验证了方法的有效性.