Education Commons^™

Magnetic And Structural Effects In Interfacial Magnetism: Molecular Magnets And Ferrimagnetic Alloys, Jenae E. Shoup

USF Tampa Graduate Theses and Dissertations

Magnetic thin films are important for technological applications such as giant magnetoresistance,spin valves and magnetic tunnel junctions. A key feature for these applications to be possible is the interface between two materials. We will be studying two types of thin film magnetism; interfaces between molecular carbon, C60, and non-magnetic/ferromagnetic material and two layers of ferrimagnetic rare earth/ transition metal alloys (RE/TM) that have similar composition to engineer a magnetic tunable interface.

One of the most unexpected spin-related properties of C60 is the emergence of room-temperature ferromagnetism in multilayer films of C60 and non-ferromagnetic transition metals such as Cu or Mn …

Spin Coupling In Magnetic Core - Shell Nanoparticles, Corisa Kons

USF Tampa Graduate Theses and Dissertations

Magnetic nanoparticles (NPs) have garnered much interest due to the unique properties that emergewhen compared to their bulk counterparts. In particular, core-shell (CS) NPs offer the ability to tailor the magnetic properties of the system through careful selection of core and shell constituent materials. In this work, the magnetic ordering of CS NPs with contrast in core/shell features (moment, anisotropy, coercivity, etc.) have been investigated using a combination of X-ray magnetic circular dichroism spectroscopy (XMCD) and polarized small angle neutron scattering (SANS). First, temperature-dependent analyses of XMCD and SANS studies were carried out for CS NPs featuring a core composed …

Material And Topographically Optimized Thermal Dissipation For High-Performance Electronic Devices Utilizing Vapor Chambers, Derek Joseph Daniels

USF Tampa Graduate Theses and Dissertations

Advances in materials science and engineering in the field of thermal transport and dissipation enable the use of higher-performance electronic devices that are smaller and generate more heat. Phase change thermal transport systems such as heat pipes and vapor chambers enable passive dissipation from devices that generate excessive heat without the need for actively pumped cooling systems. Properly designed vapor chamber enabled systems easily exceed the thermal conductivity of manufactured diamond at a small fraction of the cost.[1][2][3] While heat pipe phase change systems are generally one-dimensional with a limited cross section, vapor chambers are generally two-dimensional with a small …

Laser-Induced Modifications In Two-Dimensional Materials, Tariq Afaneh

USF Tampa Graduate Theses and Dissertations

Atomically thin two-dimensional (2D) materials have attracted a growing interest in the lastdecade from the fundamental point of view as well as their potential applications in functional devices. Due to their high surface-to-volume ratio, the physical properties of 2D materials are very sensitive to the environmental factor such as surrounding media and illumination conditions (e.g. light-mater interaction). In the first part of this dissertation I will present recent advances in developing laser-assisted methods to tune the physical properties of 2D transition metal dichalcogenides (TMDs). We demonstrate laser-assisted chemical modification ultrathin TMDs, locally replacing selenium by sulfur atoms. The photo-conversion process …

Computational Discovery Of Energetic Polynitrogen Compounds At High Pressure, Brad A. Steele

USF Tampa Graduate Theses and Dissertations

High-nitrogen-content energetic compounds containing multiple N-N bonds are an attractive alternative towards developing new generation of environmentally friendly, and more powerful energetic materials. High-N content translates into much higher heat of formation resulting in much larger energy output, detonation pressure and velocity upon conversion to large amounts of non-toxic, strongly bonded N2 gas. This thesis describes recent advances in the computational discovery of group-I alkali and hydrogen polynitrogen materials at high pressures using powerful first-principles evolutionary crystal structure prediction methods. This is highlighted by the discovery of a new family of materials that consist of long-sought after all-nitrogen N􀀀 5 …

Organometal Halide Perovskite Solar Absorbers And Ferroelectric Nanocomposites For Harvesting Solar Energy, Chaminda Lakmal Hettiarachchi

USF Tampa Graduate Theses and Dissertations

Organometal halide perovskite absorbers such as methylammonium lead iodide chloride (CH₃NH₃PbI₃-_xCl_x), have emerged as an exciting new material family for photovoltaics due to its appealing features that include suitable direct bandgap with intense light absorbance, band gap tunability, ultra-fast charge carrier generation, slow electron-hole recombination rates, long electron and hole diffusion lengths, microsecond-long balanced carrier mobilities, and ambipolarity. The standard method of preparing CH₃NH₃PbI₃-_xCl_x perovskite precursors is a tedious process involving multiple synthesis steps and, the chemicals being used (hydroiodic acid …

Understanding Gas Sorption Mechanisms In Metal–Organic Materials Via Computational Experimentation, Katherine A. Forrest

USF Tampa Graduate Theses and Dissertations

Metal–organic materials (MOMs), a type of porous crystalline structure composed of organic ligands jointed with metal ions, have captured the interest of scientists as potentially useful in gas sorption applications. Some of the most crucial avenues of investigation are in H2 storage (for use as a clean burning fuel source) and CO2 capture and sequestration (to remove the greenhouse gas from the environment).

A major advantage of MOMs for such applications is their high variability in terms of physical dimensions and chemical moieties, based on composition and synthesis conditions, making them potentially customizable for specific application if necessary structural characteristics …