Imaging skyrmions in synthetic antiferromagnetic multilayers

Skyrmions是磁性材料中的圆形磁畴/畴壁，最近在自旋电子学应用中引起了极大的兴趣。由于材料的性质，skymrions具有一种称为拓扑保护的性质，这意味着它们在相互作用时很难湮灭。此外，当它们形成在磁性层之间具有反铁磁耦合的多层膜中时，它们没有Skyrmion Hall角，因此当使用自旋极化电流来移动它们时，它们与电荷流的方向一起移动而没有偏差。skyrmions的大小取决于至关重要的多层组合物在层的组成和厚度等，在这个项目中，skyrmions在不同的材料系统将进行研究。这些材料将通过透射电子显微镜（TEM）的方法进行表征，并通过洛伦兹成像模式对磁性结构进行成像。薄膜沉积将在利兹大学进行，表征将在格拉斯哥大学进行。在连续薄膜系统中，在一定的成核场作用下，skyrmion倾向于在任意位置形成。使用各种方法，我们的目标是成核位点特异性单个孤立的skyrmions。这是建议通过局部纳米结构缺陷和操纵的磁各向异性在表面网站。原位成像将揭示，特定位置的skyrmions成核是可能的。我们还将探讨如何用自旋极化电流移动skyrmions，以展示器件应用的可能性。除了TEM工作外，还将进行光束线实验，以补充TEM成像。该项目还包括与国家物理实验室的同事合作，他们也对通过扫描探针显微镜成像感兴趣。该项目与EPSRC在研究用于自旋电子学应用的新型和先进材料系统方面的优先事项保持一致。例如，这种材料系统是一个复杂的多层结构，具有磁性和非磁性层，具有3种不同的磁性交换相互作用，为skyrmion稳定提供合适的环境。原则上，几十纳米的Skyrmions可以提供具有可控移动磁性“比特”的动态设备，但没有机械移动部件。这可以通过逻辑设备或存储器来实现。

Skyrmions are circular magnetic domains/domain walls in magnetic materials and have attracted great interest recently for spintronic applications. By the nature of the materials the skymrions possess a property known as topological protection, which means that they are hard to annihilate when they interact. Additionally when they are formed in multilayer films with antiferromagnetic coupling between the magnetic layers they have no skyrmion Hall angle, so when a spin polarised current is used to move them they move with the direction of charge flow without deviation. The size of the skymrions depend crucially on the multilayer composition in terms of layer composition and thickness etc. In this project skyrmions in different materials systems will be studied. The materials will be characterised by the methods of transmission electron microscopy (TEM) with the magnetic structure imaged by Lorentz imaging modes. Deposition of films will be carried out at the University of Leeds and the characterisation will be performed at the University of Glasgow. Skymrions with sizes less than 100 nm are to be studied.In a continuous thin film system skyrmions tend to form at random positions at a certain nucleation field. Using various approaches we aim to nucleate site specific single isolated skyrmions. This is proposed via localised nanostructured defects and manipulation of the magnetic anisotropy at surface sites. In situ imaging will reveal that site specific nucleation of skyrmions is possible. We will also explore then moving the skyrmions with spin polarised currents to demonstrate possibilities for device application. In addition to TEM work beamline experiments will also be carried out to complement the TEM imaging. The project also involves working with colleagues at the National Physical Laboratory who are also interested in imaging via scanning probe microscopy.This project aligns with EPSRC priorities in investigating new and advanced materials systems for spintronics applications. For example this materials system is a complex multilayer with magnetic and non magnetic layers possessing 3 different magnetic exchange interactions to provide the right environment for skyrmion stabilisation. In principle skyrmions down to a few 10s of nanometres can provide dynamic devices with controllable moving magnetic "bits", but without mechanical moving parts. This could be implemented logic devices or memory storage.