Manipulation of skyrmions with tailored acoustic potentials

磁skyrmions是纳米级的，粒子状的旋转自旋纹理与非零拓扑电荷，出现在一些凝聚态系统，如磁性多层膜。大约十年前，人们预测它们可以使用少量的电流沿着磁线沿着传输，这导致了它们在磁存储器和非冯·诺依曼计算架构中使用的各种建议。然而，在实践中，skyrmion运动受到磁性材料中的晶界和其他缺陷的阻碍，这意味着需要比预期更多的电流，导致主要以焦耳加热形式的能量浪费。在这个项目中，我们将完全避免使用电流，而是使用表面声波（SAW）来操纵skyrmion，而不是试图进一步改进磁性材料。博士项目的目的是进一步研究SAW对skyrmions的操纵，主要是通过实验，但辅之以微磁模拟。我们目前研究的合成反铁磁（SAF）多层膜包含比铁磁体中更小的skyrmion，并且有望实现低功率操纵，并且SAF材料将主要在本项目中进行研究。该项目的主要挑战是制造GHz频率的SAW换能器，用于操纵这些纳米级skyrmion和检测skyrmion响应。罗伊斯沉积系统和凝聚物质组内的磁性表征工具将用于存款和研究SAF多层膜。声表面波换能器将在该大学的沃尔夫森洁净室制造。将使用布拉格中心设施进行结构表征和显微镜检查。同步加速器技术将补充利兹现有的磁成像技术。

Magnetic skyrmions are nanoscale, particle-like swirling spin textures with a non-zero topological charge that appear in some condensed matter systems such as magnetic multilayers. About a decade ago it was predicted that they could be transported along a magnetic wire using small amounts of electrical current, and this has led to a variety of proposals for their use in magnetic memory and non-von Neumann computing architectures. However, in practice skyrmion motion is hindered by grain boundaries and other imperfections in the magnetic material, meaning that far more current is needed than predicted, leading to energy wastage mainly in the form of Joule heating. Rather than try to refine the magnetic material any further, what we will do in this project is avoid using currents altogether, and instead use surface acoustic waves (SAWs) to manipulate skyrmions. The aim of the PhD project is to further investigate the manipulation of skyrmions by SAWs, mainly by experiment, but complemented by micromagnetic simulations. Synthetic antiferromagnetic (SAF) multilayers that we currently study contain skyrmions that are even smaller than those in ferromagnets, and hold promise for low-power manipulation, and it is SAF materials that will mainly be investigated in this project. The main challenges of the project are to fabricate GHz frequency SAW transducers for the manipulation of these nanoscale skyrmions and to detect the skyrmion response. The Royce Deposition System and magnetic characterisation tools within the Condensed Matter Group will be used to deposit and study the SAF multilayers. SAW transducers will be fabricated in the university's Wolfson cleanroom. Structural characterisation and microscopy will be performed using Bragg Centre facilities. Synchrotron techniques will complement the magnetic imaging available in Leeds.