Using electrons to fabricate magnetic nano-circuits

畴壁（DW）存储器是一种固态磁性随机存取存储器，它控制磁畴沿纳米级磁道的运动和位置，即赛道（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的位置也可以通过包括沿RT的缺陷来控制，这些缺陷使dw在电流脉冲之间保持在适当的位置。传统的RT存储器如果扩展到三维RT系统，可以极大地提高存储密度和连通性。然而，这使得它们的制造和理解dw的行为非常具有挑战性，因为访问减少了。本博士项目的主要目的是利用聚焦电子束诱导沉积（FEBID）在原位透射电子显微镜（TEM）纳米芯片上制造3D RT存储器。这将允许复杂3D RT架构的纳米打印，并提供直接访问其局部化学，结构和控制DW运动。通过优化3D RTs的组成、几何设计和电流脉冲参数，该项目将有助于解决复杂3D纳米磁阵列中DWs运动的一致、节能控制的关键问题。学生将专注于使用FEBID制造3D RT存储器，并在TEM中表征其化学，结构和磁性。特别地，重点将放在焦耳加热/退火如何通过FEBID结构影响饱和磁化和畴壁运动。该博士生还将优化磁成像技术，以便在3D RT存储器中实时成像动态磁性。

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 main aim of this PhD project is to fabricate 3D RT memories on in-situ transmission electron microscopy (TEM) Nano-chips using focused electron beam induced deposition (FEBID). This will allow nano-printing of complex 3D RT architectures and provide direct access to their localised chemistry, structure and controlled DW motion. Through optimising the composition, geometrical design and current pulse parameters of the 3D RTs the project will help address the key issue of consistent, power-efficient control of DWs motion in complex 3D nanomagnetic arrays.The student will focus on fabricating 3D RT memories using FEBID and characterising their chemical, structural and magnetic properties within the TEM. In particular, focus will be placed on how joule heating / annealing affects the saturation magnetisation and domain wall motion through the FEBID structures. The PhD student will also optimise the magnetic imaging techniques for live imaging of dynamic magnetism within the 3D RT memories.