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Study of High Frequency Magnetisation Dynamics in Artificial Nanomagnets Using Micromagnetic Simulation and Spin Wave Spectroscopy

Dion, Troy; (2020) Study of High Frequency Magnetisation Dynamics in Artificial Nanomagnets Using Micromagnetic Simulation and Spin Wave Spectroscopy. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Study of High Frequency Magnetisation Dynamics in Artificial Nanomagnets Using Micromagnetic Simulation and Spin Wave Spectroscopy - Troy Dion.pdf - Accepted version

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V2_ASI_Resonance.mp4 - Supporting information

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Abstract

Artificial spin ice (ASI) is a metamaterial comprised of magnetic nanoislands arranged in a square or hexagonal lattice. ASI has been proposed as a reconfigurable magnonic crystal to be used in spin-wave based computing technologies. It also shares the necessary properties required for hardware-based neural networks, namely, nodes connected in a non-linear network via dipole-dipole interactions and memory capacity. In order to utilise these materials for future devices the collective magnetisation dynamics need to be explored. The frequency response can be tuned via shape anisotropy modification with differential patterning, microstate control or external magnetic field magnitude and orientation. Ferromagnetic resonance (FMR), spin-wave spectroscopy and micromagnetic simulations are used to investigate these systems. Control of the shape anisotropy by modifying the length and width of the elements in each sub-lattice of ASI can alter the magnetisation dynamics, suppress or allow modes and provide routes to microstates not practically feasible in homogeneous systems. Symmetry breaking in ASI via patterning causes degeneracy lifting and allows fingerprinting of underlying microstate using FMR which is relatively easier and quicker compared to other microstate reading techniques such as scanning probe or x-ray dichromism and can be integrated into future device designs. The effect of mode shifting due to changes in local field distributions is also discussed which is a sought after property in the field of magnonics. A one-dimensional reconfigurable magnonic crystal (1D-RMC) that can be placed in any desired microstate via topological magnetic defect injection is investigated. The system is prepared in various different microstates and spin-wave propagation is characterised. The spin-wave dispersion can be controlled by changing the pitch of reversed nanoislands. We also propose a spin-wave diode design based on these findings which may be an essential component in spin-wave based computing schemes.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Study of High Frequency Magnetisation Dynamics in Artificial Nanomagnets Using Micromagnetic Simulation and Spin Wave Spectroscopy
Event: UCL
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2020. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10113905
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