Studies in magnetoelasticity

Thesis

This thesis is divided into two halves: the first reports on the study of surface acoustic waves (SAWs) in thin magnetic films and their magnetoelastic coupling with spin waves; the second describes a study of magnetoelastic torque sensors used in electric bicycles.

Chapter 1 motivates the need for alternative computing architectures to improve performance and reduce energy consumption. One such alternative, spin-wave computing, is introduced, alongside a possible energy-efficient mechanism for spin-wave excitation using SAWs.

Chapter 2 describes the experimental process used to fabricate yttrium iron garnet zinc oxide heterostructures, in which the coupling between SAWs and spin waves can be studied.

Chapter 3 sets out a theoretical model to determine the properties of SAWs in thin film multilayers. Chapter 4 outlines a theoretical model to describe the coupling of SAWs with spin waves.

Chapter 5 presents the micro-focused Brillouin light scattering data used to analyse the samples. Firstly, the SAW transducer frequency response and SAW group velocities are measured; following this, data showing the coupling of SAWs with spin waves is presented. The coupling is highly non-reciprocal, which agrees with the predictions from the theoretical model. Finally, in Chapter 6, concluding remarks on this first part of the thesis are given.

Authors: Ryburn, F

• DOI: 10.5287/ora-amv8ayyba
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: phonon; spin wave; surface acoustic wave; magnon; magnonics; multilayer thin films; magnetoelastic coupling; magnetoelasticity; magnon computing
• Subjects: Acoustic surface waves; Physics; Magnetism