Raftrey David, Finizio Simone, Chopdekar Rajesh V, Dhuey Scott, Bayaraa Temuujin, Ashby Paul, Raabe Jörg, Santos Tiffany, Griffin Sinéad, Fischer Peter
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
Physics Department, University of California Santa Cruz, Santa Cruz, CA 95064, USA.
Sci Adv. 2024 Oct 4;10(40):eadp8615. doi: 10.1126/sciadv.adp8615. Epub 2024 Oct 2.
Magnetic skyrmions have so far been treated as two-dimensional spin structures characterized by a topological winding number. However, in real systems with the finite thickness of the device material being larger than the magnetic exchange length, the skyrmion spin texture extends into the third dimension and cannot be assumed as homogeneous. Using soft x-ray laminography, we reconstruct with about 20-nanometer spatial (voxel) size the full three-dimensional spin texture of a skyrmion in an 800-nanometer-diameter and 95-nanometer-thin disk patterned into a 30× [iridium/cobalt/platinum] multilayered film. A quantitative analysis finds that the evolution of the radial profile of the topological skyrmion number is nonuniform across the thickness of the disk. Estimates of the micromagnetic energy densities suggest that the changes in topological profile are related to nonuniform competing energetic interactions. Our results provide a foundation for nanoscale metrology for spintronics devices using topology as a design parameter.
迄今为止，磁斯格明子一直被视为具有拓扑缠绕数特征的二维自旋结构。然而，在器件材料厚度有限且大于磁交换长度的实际系统中，斯格明子自旋纹理会延伸到第三维度，且不能假定为均匀的。利用软X射线断层成像技术，我们以约20纳米的空间（体素）尺寸重建了一个直径800纳米、厚度95纳米的磁盘中斯格明子的完整三维自旋纹理，该磁盘被图案化为30×[铱/钴/铂]多层膜。定量分析发现，拓扑斯格明子数的径向分布在磁盘厚度方向上的演变是不均匀的。微磁能密度的估计表明，拓扑分布的变化与不均匀的竞争能量相互作用有关。我们的结果为将拓扑作为设计参数的自旋电子器件的纳米级计量学提供了基础。
