Skyrmions have attracted significant interest due to their topological spin structures and fascinating physical features. The skyrmion phase arises in materials with Dzyaloshinskii-Moriya (DM) interaction at interfaces or in volume of non-centrosymmetric materials. However, although skyrmions were generated experimentally, one critical intrinsic relationship between fabrication, microstructures, magnetization and the existence of skyrmions remains to be established. Here, two series of CoFeB ultrathin films with controlled atomic scale structures are employed to reveal this relationship. By inverting the growth order, the amount of defects can be artificially tuned, and skyrmions are shown to be preferentially formed at defect sites. The stable region and the density of the skyrmions can be efficiently controlled in the return magnetization loops by utilizing first-order reversal curves to reach various metastable states. These findings establish the general and intrinsic relationship from sample preparation to skyrmion generation, offering an universal method to control skyrmion density.
Excitation and detection of short-waved spin waves in ultrathin Ta/CoFeB/MgO-layer system suitable for spin-orbit-torque magnonics
我们报告的激发和检测的短波自旋波的波矢高达约$40\,\mathrm{rad}\,μ\mathrm{m}^{-1}$自旋波波导制成的，在平面内磁化的Co $_{8}$ Fe $_{72}$ B $_{20}$（CoFeB）。CoFeB被并入Ta/CoFeB/MgO的层堆叠中，该层堆叠是具有大的自旋轨道转矩和大的垂直磁各向异性常数的层系统。短波自旋波由纳米共面波导激发，并通过自旋整流和微聚焦布里渊光散射光谱检测。我们发现，大的垂直磁各向异性的自旋波寿命大大受益，导致在没有界面阻尼的散装系统的寿命相媲美。所提出的结果铺平了道路，成功地扩展磁振子的非对称层堆叠具有大的自旋轨道扭矩。
Dynamics of domain growth driven by dipolar interactions in a perpendicularly magnetized ultrathin film
对垂直磁化的Fe/2 ML Ni/W（110）双金属薄膜的交流磁化率的测量表明，该系统支持的条纹状畴结构中畴生长和畴密度变化的动力学特征是清晰的。在0.20 K/s < R < 0.70 K/s范围内，随着升温速率的增加，磁化率峰向高温移动。使用松弛模型的分析表明，定量的动力学驱动的非平衡域密度在（近）零场（即偶极相互作用），和温度的变化是由于响应时间由局部域壁段的钉扎结构缺陷。由偶极相互作用驱动的畴密度弛豫的基本时间尺度比由外加场驱动的单个巴克豪森步骤的基本时间尺度慢10^5倍。基本时间尺度的增加反映了偶极子和塞曼能量的相对大小，以及需要许多局部畴壁段的相关运动来影响畴生长。
Magnetic phase transitions in Ta/CoFeB/MgO multilayers
我们研究了Ta/Co $_{20}$ Fe $_{60}$ B $_{20}$ /MgO多层膜的电输运特性和磁性隧道结纳米柱。这些测量结果表明，在Co $_{20}$ Fe $_{60}$ B $_{20}$ /MgO界面处形成了磁性氧化物层。在大约160 K时，氧化物经历从低温下的绝缘反铁磁体到高温下的导电弱铁磁体的相变。这种界面磁性氧化物有望对用于自旋扭矩存储器的CoFeB基多层膜的磁性产生重大影响。
Tailoring Ultrathin Magnetic Multilayers at Terraced Topologically Insulating Interfaces for Perpendicularly Magnetized Domains
University of Leeds（利兹大学）；ISIS Neutron and Muon Source, STFC Rutherford Appleton Laboratory（STFC卢瑟福阿普尔顿实验室中子与μ子源）；Diamond Light Source（钻石光源）；Imperial College London（伦敦帝国理工学院）
Collective Coordinate Descriptions of Magnetic Domain Wall Motion in Perpendicularly Magnetized Nanostructures under the Application of In-plane Fields
