A high-pressure apparatus with in situ electron spin resonance probe for the characterization of phase transitions in magnetic materials and superconductors

I have developed a sapphire ball cell high pressure apparatus with an in situ microwave electron spin resonance (ESR) probe for the study of phase transitions in magnetic materials and superconductors at microwave frequencies (10 GHz). The resonant structure is based on two sapphire ball dielectric resonators which also serve to compress a gasket enclosed sample region. This high pressure microwave apparatus facilitates the study of the magnetic properties of materials as a function of pressure, temperature, and applied magnetic field. In this dissertation, I present the design, fabrication, and application of the sapphire ball cell cavity in our physics laboratory to the study of both colossal magnetoresistive and superconducting materials. My presentation includes an introduction to methods of high pressure research and microwave spectroscopy as well as detailed descriptions of the methods of pressure generation, pressure calibration, and the characterization of phase transitions within our specific experiments.; To design the resonant microwave cavity structures used in my experiments, I incorporated a number of computational techniques for the solution of the electromagnetic wave equation. These techniques have led to other interesting projects. I will discuss one of these projects in my final chapter where I present an analytical, computational, and experimental study of an effective dielectric medium with plasmonic response at microwave frequencies.