Imaging skyrmions in synthetic antiferromagnetic multilayers

Skyrmions是磁性材料中的圆形磁畴/畴壁，近年来引起了人们对自旋电子学应用的极大兴趣。根据材料的性质，天空粒子具有一种被称为拓扑保护的特性，这意味着它们在相互作用时很难被湮灭。此外，当它们在多层膜中形成时，磁性层之间具有反铁磁耦合，它们没有斯基米子霍尔角，因此当使用自旋极化电流移动它们时，它们与电荷流动方向移动而没有偏差。天际线的大小主要取决于多层的组成，包括层的组成和厚度等。在这个项目中，将研究不同材料系统中的天空。材料将通过透射电子显微镜（TEM）的方法进行表征，并用洛伦兹成像模式对其磁性结构进行成像。电影的沉积将在利兹大学进行，刻画将在格拉斯哥大学进行。尺寸小于100纳米的skyymrions将被研究。在连续的薄膜体系中，在一定的成核场下，粒子倾向于在随机位置形成。使用各种方法，我们的目标是形成特定地点的单个孤立的天空。这是通过局部纳米结构缺陷和对表面磁各向异性的操纵提出的。原位成像将显示，特定部位的核是可能的。我们还将探索用自旋极化电流移动天幕，以展示设备应用的可能性。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，具有磁性和非磁性层，具有3种不同的磁交换相互作用，为skyrmion稳定提供合适的环境。原则上，小到几十纳米的skyrmions可以为动态设备提供可控的移动磁“位”，但没有机械运动部件。这可以通过逻辑器件或存储器来实现。

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.