Microwave delay echoes in insulating ferrimagnetic single crystals

Adam, John D. (1967) Microwave delay echoes in insulating ferrimagnetic single crystals. MSc(R) thesis, University of Glasgow.

Abstract

This thesis describes experimental observations on the parametric amplification, in single crystal Yttrium Iron Garnet of elastic, magnetoelastic modes, by application of a pump pulse of twice the frequency of the L-band micro-wave signal pulse, and the excitation of a delayed pulse by the application of two time separated microwave pulses of the frequency. Details of experiments performed to determine the internal magnetostatic field profile of a magnetised rectangular cross-section Yttruim Iron Garnet rod are derived. The experimental internal fields are compared with those derived theoretically. It was found to be possible to reduce the attenuation of elastic echoes by parametric amplification. Details are given of saturation levels, attenuation and timing of the pump pulse. In the magnetolelastic regime details are given of the variation of gain wit, timing of the pump pulse, pump power, signal power orientation of the rod to the external field. Magnetostatic propagating mode, the amplitude of the parametrically excited echo is plotted against, time of application of the pump pulse, pump power and signal power. Magnetostatic standing wave mode, the amplitude of the parametrically excited echo is plotted against, time application of the pump pulse, pump power and signal power. Magnetostatic wave mode echo, parametrically excited by the application of two time separated pulses of the same frequency, plots are shown of gain relative to the first pulse with variation of, second pulse amplitude, the first pulse amplitude and time between the application of the two pulses. Parametric amplification of magnetostatic modes due to subsidiary absorbtion of the pump frequency. Plots of attenuation of the delayed pulse against signal power, pump power and time of application of the pump pulse are given. This is found to be a two port phenomenon. At L-band subsidiary absorbtion is coincident with the main absorbtion, due to the low signal frequency used, 12KMc/s, the ends of the rod were not saturated.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Keywords: Electromagnetics.
• Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering
• Supervisor's Name: Collins, Mr. J.H.
• Date of Award: 1967
• Depositing User: Enlighten Team
• Unique ID: glathesis:1967-73326
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jun 2019 08:56
• Last Modified: 10 May 2022 15:09
• Thesis DOI: 10.5525/gla.thesis.73326
• URI: https://theses.gla.ac.uk/id/eprint/73326