Studies in magnon spintronics

This thesis is a thesis of two halves. The first investigates the Spintronic idea of generating charge-decoupled spin currents in metallic systems, whereas the second contains discussions on the topic of Magnon Computing. Chapters 2 and 3 investigate the relevance of the ‘old knowledge’ of Magnetic Resonance to the modern-day research field of Spintronics. A model based on the Overhauser Effect is presented that explains microscopically how a pure spin current can be generated in a metallic bilayer system, and an experiment is proposed to explore this model, which is dubbed the ‘Overhauser Spin Battery’. Chapter 3 contains details of all three aspects of the Spin Battery experimental process - that of sample fabrication, sample experimentation, and a presentation of the results. The results support the model presented in Chapter 2, and suggest that the Overhauser Spin Battery can indeed be used to generate pure spin currents. Chapter 4 looks at the problem of how information is encoded into magnonic streams. A simple device for converting between amplitude modulated (AM) and phase modulated (PM) signals is demonstrated. Potential novel applications of this device are also considered. Chapter 5 investigates methods of separating magnonic signals of differing frequencies that have been transmitted down a single waveguide simultaneously, which is known as multiplexing. It was determined that heterodyning is a viable method for extracting signals from a multiplexed data stream, and that it is applicable to both AM and PM signals. Quadrature phase-shift keying is shown to be a valid method for doubling the information transmitted down a magnonic waveguide, and a discussion is presented about how the principles of phase-shift keying could be applied to wider questions in Magnon Computing. Chapter 6 summarises the key ideas and results of the thesis, and considers some further experiments that may be of interest.