Multi-modal electron microscopy of 3D racetrack memory

现代社会越来越依赖数字数据，然而大多数数据存储在消耗大量能源和可靠性有限的磁盘驱动器上。随着数据中心和服务器数量的增长，探索更高效的未来数字存储技术变得越来越有必要。域墙(DW)存储器是一种固态磁随机存取存储器，它控制磁畴沿纳米级磁道的运动和位置，即跑道(RT)存储器。DWS的磁矩是通过在外加电流脉冲中传递电子的自旋角动量来驱动的。DW的位置也可以通过沿RT包含缺陷来控制，这些缺陷将DW固定在电流脉冲之间。如果将传统的RT存储器扩展到三维(3D)RT系统，则可以极大地提高其存储密度和连通性。然而，这使得他们的制作和理解DW的行为非常具有挑战性，因为访问减少。本项目的目标是使用先进的电子显微镜技术来构建3D RT存储器，提供对其在手术条件下(电流脉冲和加热)下的化学、结构和DW运动的直接的纳米尺度分析。这将允许对其操作进行有效的工程设计，将3D RTS的功能性能带入一个全新的理解领域。通过优化3DRTS的组成、几何设计和电流脉冲参数，我们可以解决在复杂的3D纳米磁阵列中一致、高效地控制DWS运动的关键问题。这一结果不仅将导致高影响力的出版物和会议演讲，而且还将为将自旋电子学领域扩展到具有复杂3D几何结构的先进纳米磁系统提供丰富的信息。

Modern society is becoming increasingly reliant on digital data, yet most data is stored on magnetic hard disk drives that consume large amounts of energy and are limited in reliability. As data centres and volumes of servers grow it is becoming necessary to explore more efficient future digital storage technologies.Domain wall (DW) memory is a type of solid-state magnetic random-access memory that controls the motion and position of magnetic domains along a nano-scale magnetic track, i.e., racetrack (RT) memory. The magnetic moments of DWs are driven by transferring spin angular momentum from electrons in an applied current pulse. The position of the DWs can also be controlled by including defects along the RT that hold the DWs in place between current pulses.Conventional RT memories can vastly improve their storage density and connectivity if they expand into three-dimensional (3D) RT systems. However, this makes their fabrication and understanding the behaviour of DWs very challenging due to reduced access.The aim of this project is to use advanced electron microscopy techniques to construct 3D RT memories that provide direct, nano-scale analysis of their chemistry, structure and DW motion under operando conditions (current pulsing and heating). This will allow effective engineering of their operation, taking the functional performance of 3D RTs into a brand-new realm of understanding. Through optimising the composition, geometrical design and current pulse parameters of the 3D RTs we can address the key issue of consistent, power-efficient control of DWs motion in complex 3D nanomagnetic arrays.The results will not only lead to high impact publications and conference presentations, but also provide a wealth of information for expanding the field of spintronics into advanced nanomagnetic systems with complex 3D geometries.