Three-dimensional magnetic textures in strongly coupled cylindrical nanowires

  • John Fullerton

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

Over the past few decades, the field of nanomagnetism has brought profound technological advances into the world. This extremely successful research area has both revealed and allowed the control of a rich variety of magnetic phenomena such as domain walls and skyrmions. Spintronic technologies in particular show great promise for meeting the demands of future computing and data storage applications. However, the focus so far has largely been on two-dimensional (2D) thin film systems that do not fully utilise the spin textures and geometries allowed in three-dimensional (3D) space. For example, for most data storage devices we remain as a 3D observer exerting an influence on a 2D system, whether that be in the form of a person writing information on a piece of paper, or a read/write head over a spinning hard drive. The ability to now study 3D magnetic nanostructures has been made possible by advances in fabrication methods. In this thesis, we utilise the 3D nanoprinting technique focused electron beam induced deposition (FEBID), which allows the direct deposition of fully functional 3D nanostructures. Through the use of FEBID experimentally, and replicating the process in simulations, we study how to create and influence 3D magnetic textures in coupled nanostructures.

A move to 3D systems brings with it new and exciting research challenges. In this thesis, we aim to contribute overcoming some of them and as such, we present results in three categories: using micromagnetic simulations to understand the impact of coupling between nanowires and growth mechanism employed when using FEBID; assessing the viability of iron FEBID for the creation of free-standing nanostructures; and uncovering the influence of geometry and material purity on the magnetisation and reversal process in cobalt FEBID nanohelices. Consequently, we demonstrate how 3D magnetic textures can be created and controlled through: the design of coupled nanostructures, understanding of the nano-printing process, and tuning material properties. We further explore the potential to control the magnetisation in a 3D space.

Thesis is embargoed until 31 December 2026.
Date of AwardDec 2023
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsUniversity of Glasgow & Engineering & Physical Sciences Research Council
SupervisorDonald A. Maclaren (Supervisor), Amalio Fernández-Pacheco (Supervisor) & Miryam Arredondo (Supervisor)

Keywords

  • Nanomagnetism
  • electron microscopy
  • focused electron beam induced deposition
  • nanofabrication
  • nanowires
  • x-ray microscopy
  • micromagnetic modelling

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