Topological Structures in Ferroic Materials
type: CreativeWork
description: The study of topological defects in condensed matter involves those regions in which the chosen order parameter ceases to vary continuously, such as points, lines, and surfaces. In ferroic materials, these defects include planar domain walls, which separate regions of uniform orientation of the order parameter, as well as more complex structures such as vortices and skyrmions, which are spiralling configurations of the order parameter. This thesis investigates topological structures arising in both magnetic and ferroelectric structures, highlighting both the similarities and the differences in these material systems. The first experiment outlined in this thesis is the growth and characterisation of thin films of CoxZnyMnz alloys. Previous work by Tokunaga et al has shown that alloys of CoxZnyMnz (x+y+z=20) crystallise in the -Mn structure, which is non-centrosymmetric and analogous to the B20 structure of common skyrmion-hosting materials such as MnSi. These alloys were shown to exhibit a skyrmion phase at moderate fields just below their Curie temperature, which for some compositions was close to room temperature; an essential feature for potential skyrmion-based devices. Results in the literature also provide evidence that the reduced dimensionality of thin plates or films of skyrmion-hosting materials can increase the range of the skyrmion phase across the field-temperature phase diagram. Consequently, growing thin films of these CoxZnyMnz alloys could prove advantageous. In this thesis, the successful growth of polycrystalline CoxZnyMnz thin films using magnetron sputtering on a lattice-matched BaF2 single-crystal substrate is demonstrated. Crystal structure was confirmed to be the -Mn structure in polycrystalline form by x-ray diffraction (XRD) and electron diffraction performed by transmission electron microscopy (TEM). In addition, the stoichiometry of the alloys was confirmed to be the required ratios using energy dispersive x-ray spectroscopy (EDX) via bo…
abstract: The study of topological defects in condensed matter involves those regions in which the chosen order parameter ceases to vary continuously, such as points, lines, and surfaces. In ferroic materials, these defects include planar domain walls, which separate regions of uniform orientation of the order parameter, as well as more complex structures such as vortices and skyrmions, which are spiralling configurations of the order parameter. This thesis investigates topological structures arising in both magnetic and ferroelectric structures, highlighting both the similarities and the differences in these material systems. The first experiment outlined in this thesis is the growth and characterisation of thin films of CoxZnyMnz alloys. Previous work by Tokunaga et al has shown that alloys of CoxZnyMnz (x+y+z=20) crystallise in the -Mn structure, which is non-centrosymmetric and analogous to the B20 structure of common skyrmion-hosting materials such as MnSi. These alloys were shown to exhibit a skyrmion phase at moderate fields just below their Curie temperature, which for some compositions was close to room temperature; an essential feature for potential skyrmion-based devices. Results in the literature also provide evidence that the reduced dimensionality of thin plates or films of skyrmion-hosting materials can increase the range of the skyrmion phase across the field-temperature phase diagram. Consequently, growing thin films of these CoxZnyMnz alloys could prove advantageous. In this thesis, the successful growth of polycrystalline CoxZnyMnz thin films using magnetron sputtering on a lattice-matched BaF2 single-crystal substrate is demonstrated. Crystal structure was confirmed to be the -Mn structure in polycrystalline form by x-ray diffraction (XRD) and electron diffraction performed by transmission electron microscopy (TEM). In addition, the stoichiometry of the alloys was confirmed to be the required ratios using energy dispersive x-ray spectroscopy (EDX) via bo…
author: Mackel, Jennifer
language: eng
date published: 2020-7
date modified: 2026-07-24T03:55:18Z
provider: Queen's University Belfast
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Queen's University Belfast