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Articles 121 - 150 of 468
Full-Text Articles in Condensed Matter Physics
Quantitative Probing Of Vacancies And Ions Dynamics In Electroactive Oxide Materials, Jiaxin Zhu
Quantitative Probing Of Vacancies And Ions Dynamics In Electroactive Oxide Materials, Jiaxin Zhu
Doctoral Dissertations
Oxygen vacancy and ion dynamics in functional oxides are critical factors influencing electrical conductivity and electrochemical activity of oxides assemblies. The recent advancements in deposition and fabrication of oxide heterostructured films with atomic-level precision has led to discovery of intriguing physical properties and new artificial materials. While still under debate, researchers most often attribute these observed behaviors to unique oxygen vacancy distributions in the substrate near heterointerfaces. In electroactive oxides devices such as solid oxide cells (SOCs), oxygen vacancy and ion transport at the triple-phase boundary determines the performance of the device. This complex process motivates numerous remaining questions regarding …
Probing Quantized Excitations And Many-Body Correlations In Transition Metal Dichalcogenides With Optical Spectroscopy, Shao-Yu Chen
Probing Quantized Excitations And Many-Body Correlations In Transition Metal Dichalcogenides With Optical Spectroscopy, Shao-Yu Chen
Doctoral Dissertations
Layered transition metal dichalcogenides (TMDCs) have attracted great interests in recent years due to their physical properties manifested in different polytypes: Hexagonal(H)-TMDC,which is semiconducting, exhibits strong Coulomb interaction and intriguing valleytronic properties; distorted octahedral(T’)-TMDC,which is semi-metallic, is predicted to exhibit rich nontrivial topological physics. In this dissertation,we employ the polarization-resolved micron-Raman/PL spectroscopy to investigate the optical properties of the atomic layer of several polytypes of TMDC. In the first part for polarization-resolved Raman spectroscopy, we study the lattice vibration of both H and T’-TMDC, providing a thorough understanding of the polymorphism of TMDCs. We demonstrate that Raman spectroscopy is a …
Electromagnon Excitation In Cupric Oxide Measured By Fabry-Pérot Enhanced Terahertz Mueller Matrix Ellipsometry, Sean Knight, Dharmalingam Prabhakaran, Christian Binek, Mathias Schubert
Electromagnon Excitation In Cupric Oxide Measured By Fabry-Pérot Enhanced Terahertz Mueller Matrix Ellipsometry, Sean Knight, Dharmalingam Prabhakaran, Christian Binek, Mathias Schubert
Christian Binek Publications
Here we present the use of Fabry-Pérot enhanced terahertz (THz) Mueller matrix ellipsometry to measure an electromagnon excitation in monoclinic cupric oxide (CuO). As a magnetically induced ferroelectric multiferroic, CuO exhibits coupling between electric and magnetic order. This gives rise to special quasiparticle excitations at THz frequencies called electromagnons. In order to measure the electromagnons in CuO, we exploit single-crystal CuO as a THz Fabry-Pérot cavity to resonantly enhance the excitation’s signature. This enhancement technique enables the complex index of refraction to be extracted. We observe a peak in the absorption coefficient near 0.705 THz and 215 K, which corresponds …
Phonon Order And Reststrahlen Bands Of Polar Vibrations In Crystals With Monoclinic Symmetry, Mathias Schubert, Alyssa Mock, Rafal Korlacki, Vanya Darakchieva
Phonon Order And Reststrahlen Bands Of Polar Vibrations In Crystals With Monoclinic Symmetry, Mathias Schubert, Alyssa Mock, Rafal Korlacki, Vanya Darakchieva
Department of Electrical and Computer Engineering: Faculty Publications
In this Rapid Communication, we present the order of the phonon modes and the appearance of the reststrahlen bands for monoclinic symmetry materials with polar lattice vibrations. Phonon modes occur in associated pairs of transverse and longitudinal optical modes, and pairs either belong to inner or outer phonon modes. Inner modes are nested within outer modes. Outer modes cause polarization-dependent reststrahlen bands. Inner modes cause polarization-independent reststrahlen bands. The directional limiting frequencies within the Born-Huang approach are bound to within outer mode frequency regions not occupied by inner mode pairs. Hence, an unusual phonon mode order can occur where both …
Longitudinal Phonon Plasmon Mode Coupling In Β-Ga2O3, Mathias Schubert, Alyssa Mock, Rafal Korlacki, Sean Knight, Zbigniew Galazka, Günther Wagner, Virginia Wheeler, Marko Tadjer, Ken Goto, Vanya Darakchieva
Longitudinal Phonon Plasmon Mode Coupling In Β-Ga2O3, Mathias Schubert, Alyssa Mock, Rafal Korlacki, Sean Knight, Zbigniew Galazka, Günther Wagner, Virginia Wheeler, Marko Tadjer, Ken Goto, Vanya Darakchieva
Department of Electrical and Computer Engineering: Faculty Publications
In this letter, we investigate a set of n-type single crystals of monoclinic symmetry β-Ga2O3 with different free electron concentration values by generalized far infrared and infrared spectroscopic ellipsometry. In excellent agreement with our previous model prediction, we find here by experiment that longitudinal-phonon-plasmon coupled modes are polarized either within the monoclinic plane or perpendicular to the monoclinic plane. As predicted, all modes change the amplitude and frequency with the free electron concentration. The most important observation is that all longitudinal-phonon-plasmon coupled modes polarized within the monoclinic plane continuously change their direction as a function of …
Lattice Dynamics Of Orthorhombic Ndgao3, Alyssa Mock, Rafal Korlacki, Sean Knight, Megan Stokey, Alex Fritz, Vanya Darakchieva, Mathias Schubert
Lattice Dynamics Of Orthorhombic Ndgao3, Alyssa Mock, Rafal Korlacki, Sean Knight, Megan Stokey, Alex Fritz, Vanya Darakchieva, Mathias Schubert
Department of Electrical and Computer Engineering: Faculty Publications
A complete set of infrared-active and Raman-active lattice modes is obtained from density functional theory calculations for single-crystalline centrosymmetric orthorhombic neodymium gallate. The results for infrared-active modes are compared with an analysis of the anisotropic long-wavelength properties using generalized spectroscopic ellipsometry. The frequency-dependent dielectric function tensor and dielectric loss function tensor of orthorhombic neodymium gallium oxide are reported in the spectral range of 80–1200 cm−1. A combined eigendielectric displacement vector summation and dielectric displacement loss vector summation approach augmented by considerations of lattice anharmonicity is utilized to describe the experimentally determined tensor elements. All infrared-active transverse and longitudinal …
Limitations Of Zt As A Figure Of Merit For Nanostructured Thermoelectric Materials, Xufeng Wang, Mark Lundstrom
Limitations Of Zt As A Figure Of Merit For Nanostructured Thermoelectric Materials, Xufeng Wang, Mark Lundstrom
Department of Electrical and Computer Engineering Faculty Publications
Thermoelectric properties of nanocomposites are numerically studied as a function of average grain size or nanoparticle density by simulating the measurements as they would be done experimentally. In accordance with previous theoretical and experimental results, we find that the Seebeck coefficient, power factor and figure of merit, zT, can be increased by nanostructuring when energy barriers exist around the grain boundaries or embedded nanoparticles. When we simulate the performance of a thermoelectric cooler with the same material, however, we find that the maximum temperature difference is much less than expected from the given zT. This occurs because the …
Proximitized Materials, Igor Žutić, Alex Matos-Abiague, Benedikt Scharf, Hanan Dery, Kirill Belashchenko
Proximitized Materials, Igor Žutić, Alex Matos-Abiague, Benedikt Scharf, Hanan Dery, Kirill Belashchenko
Kirill Belashchenko Publications
Advances in scaling down heterostructures and having an improved interface quality together with atomically thin two-dimensional materials suggest a novel approach to systematically design materials. A given material can be transformed through proximity effects whereby it acquires properties of its neighbors, for example, becoming superconducting, magnetic, topologically nontrivial, or with an enhanced spin–orbit coupling. Such proximity effects not only complement the conventional methods of designing materials by doping or functionalization but also can overcome their various limitations. In proximitized materials, it is possible to realize properties that are not present in any constituent region of the considered heterostructure. While the …
Coupling Of Light's Orbital Angular Momentum To A Quantum Dot Ensemble, Alaa A. Bahamran
Coupling Of Light's Orbital Angular Momentum To A Quantum Dot Ensemble, Alaa A. Bahamran
Electronic Theses and Dissertations
We theoretically and experimentally investigate the transfer of orbital angular momentum from light to an ensemble of semiconductor-based nanostructures composed of lead sulfide quantum dots. Using an ensemble of quantum dots offers a higher cross-section and more absorption of twisted light fields compared to experimentally challenging single-nanostructure measurements. However, each quantum dot (except for on-center) sees a displaced light beam parallel to its own axis of symmetry. The transition matrix elements for the light-matter interaction are calculated by expressing the displaced light beam in terms of the appropriate light field centered on the nanoparticles. The resulting transition rate induced by …
Scanning Probe Microscopy Measurements On 2d Materials And Iridates, Armin Ansary
Scanning Probe Microscopy Measurements On 2d Materials And Iridates, Armin Ansary
Theses and Dissertations--Physics and Astronomy
In the past two decades, there has been a quest to understand and utilize novel materials such as iridates and two-dimensional (2D) materials. These classes of materials show a lot of interesting properties both in theoretical predictions as well as experimental results. Physical properties of some of these materials have been investigated using scanning probe measurements, along with other techniques.
One-dimensional (1D) catalytic etching was investigated in few-layer hexagonal boron nitride (hBN) films. Etching of hBN was shown to share several similarities with that of graphitic films. As in graphitic films, etch tracks in hBN commenced at film edges and …
Electron Transport In One And Two Dimensional Materials, Samuel William Lagasse
Electron Transport In One And Two Dimensional Materials, Samuel William Lagasse
Legacy Theses & Dissertations (2009 - 2024)
This dissertation presents theoretical and experimental studies in carbon nanotubes (CNTs), graphene, and van der Waals heterostructures. The first half of the dissertation focuses on cutting edge tight-binding-based quantum transport models which are used to study proton irradiation-induced single-event effects in carbon nanotubes [1], total ionizing dose effects in graphene [2], quantum hall effect in graded graphene p-n junctions [3], and ballistic electron focusing in graphene p-n junctions [4]. In each study, tight-binding models are developed, with heavy emphasis on tying to experimental data. Once benchmarked against experiment, properties of each system which are difficult to access in the laboratory, …
Straintronic Nanomagnetic Devices For Non-Boolean Computing, Md Ahsanul Abeed
Straintronic Nanomagnetic Devices For Non-Boolean Computing, Md Ahsanul Abeed
Theses and Dissertations
Nanomagnetic devices have been projected as an alternative to transistor-based switching devices due to their non-volatility and potentially superior energy-efficiency. The energy efficiency is enhanced by the use of straintronics which involves the application of a voltage to a piezoelectric layer to generate a strain which is ultimately transferred to an elastically coupled magnetostrictive nanomaget, causing magnetization rotation. The low energy dissipation and non-volatility characteristics make straintronic nanomagnets very attractive for both Boolean and non-Boolean computing applications. There was relatively little research on straintronic switching in devices built with real nanomagnets that invariably have defects and imperfections, or their adaptation …
Transient Transmission Oscillations In Doped And Undoped Lithium Niobate Induced By Near-Infrared Femtosecond Pulses, Bryan J. Crossman, Gregory J. Taft
Transient Transmission Oscillations In Doped And Undoped Lithium Niobate Induced By Near-Infrared Femtosecond Pulses, Bryan J. Crossman, Gregory J. Taft
Physics Faculty Publications
Transient transmission oscillations in X-cut and Z-cut congruent, iron-doped, and magnesium-doped lithium niobate samples were measured using 50 fs, 800 nm, 0.5 nJ pulses from a self-mode-locked Ti:sapphire laser in an optical pump–probe system. Several Raman-active oscillation modes excited by these pulses were observed as changes in the transmitted probe intensity versus time delay between the pump and probe pulses. The samples were rotated to determine how the incident polarization of the pump pulses affects the mode excitations. The observed Raman-active oscillations correspond to previously reported symmetry modes measured with traditional, continuous-wave, Raman spectroscopy using the same scattering …
Physical Electronic Properties Of Self-Assembled 2d And 3d Surface Mounted Metal-Organic Frameworks, Radwan Elzein
Physical Electronic Properties Of Self-Assembled 2d And 3d Surface Mounted Metal-Organic Frameworks, Radwan Elzein
USF Tampa Graduate Theses and Dissertations
Metal-organic frameworks stand at the frontiers of molecular electronic research because they combine desirable physical properties of organic and inorganic components. They are crystalline porous solids constructed by inorganic nodes coordinated to organic ligands to form 1D, 2D, or 3D structures. They possess unique characteristics such as ultrahigh surface area crystal lattices up to 10000 m2 g-1, and tunable nanoporous sizes ranging from 0.2 to 50 nm. Their unprecedented structural diversity and flexibility beyond solid state materials can lead to unique properties such as tailorable electronic and ionic conductivity which can serve as interesting platforms for a …
Genetic Algorithm Design Of Photonic Crystals For Energy-Efficient Ultrafast Laser Transmitters, Troy A. Hutchins-Delgado
Genetic Algorithm Design Of Photonic Crystals For Energy-Efficient Ultrafast Laser Transmitters, Troy A. Hutchins-Delgado
Shared Knowledge Conference
Photonic crystals allow light to be controlled and manipulated such that novel photonic devices can be created. We are interested in using photonic crystals to increase the energy efficiency of our semiconductor whistle-geometry ring lasers. A photonic crystal will enable us to reduce the ring size, while maintaining confinement, thereby reducing its operating power. Photonic crystals can also exhibit slow light that will increase the interaction with the material. This will increase the gain, and therefore, lower the threshold for lasing to occur. Designing a photonic crystal for a particular application can be a challenge due to its number of …
Two-Dimensional Layered Materials (Graphene-Mos2) Nanocatalysts For Hydrogen Production, Jacob Dobler, Taylor Robinson, Sanju Gupta 7455940
Two-Dimensional Layered Materials (Graphene-Mos2) Nanocatalysts For Hydrogen Production, Jacob Dobler, Taylor Robinson, Sanju Gupta 7455940
Posters-at-the-Capitol
Recent development of two-dimensional layered materials including graphene-family and related nanomaterials have arisen as potential game changer for energy, water and sensing applications. While graphene is a form of carbon arranged hexagonally within atomic thin sheet, MoS2 is becoming a popular, efficient, and cost-effective catalyst for electrochemical energy devices, in contrast to expensive platinum and palladium catalysts. In this work, we electrochemically desulfurize few-layer molybdenum disulfide (MoS2) and aerogels with reduced graphene oxide (rGO) prepared under hydrothermal conditions ((P< 20 bar, T< 200 oC), for improving hydrogen evolution reaction (HER) activity via point defects (S-vacancy). Moreover, the interactions between rGO …
Physical Properties Of Engineered Nanocomposites For Defense Applications, Alex Henson, Sanju Gupta
Physical Properties Of Engineered Nanocomposites For Defense Applications, Alex Henson, Sanju Gupta
Posters-at-the-Capitol
Polymer nanocomposites are significant for modern and future technologies (aerospace, defense, water purification etc.) due to their tailored properties, lightweight and low cost. However, ‘forward’ engineered polymer (host matrix) composites with smaller size nanoparticles (guest) providing desired properties targeting specific applications remains a challenging task as they depend largely on nanoparticles size, shape and loading (volume fraction). This study develops polymer nanocomposites impregnated with ‘organic-inorganic’ silsesquioxane nanoparticles and graphene nanoribbons, and investigates microscopic structure and dynamics of interfacial layer to predict macroscale properties. The nanocomposites consist of poly(2-vinylpyridine) (P2VP) polymer (segment ~5nm) with spherical silsesquioxane nanoparticles (diameter ~2-5nm) and planar …
Magnetoelectric Memory Cells With Domain-Wall-Mediated Switching, Kirill Belashchenko, Oleg Tchernyshyov, Alexey Kovalev, Dmitri Nikonov
Magnetoelectric Memory Cells With Domain-Wall-Mediated Switching, Kirill Belashchenko, Oleg Tchernyshyov, Alexey Kovalev, Dmitri Nikonov
Kirill Belashchenko Publications
A magnetoelectric memory cell with domain - wall - mediated switching is implemented using a split gate architecture . The split gate architecture allows a domain wall to be trapped within a magnetoelectric antiferromagnetic ( MEAF ) active layer . An extension of this architecture applies to multiple gate linear arrays that can offer advantages in memory density , programmability , and logic functionality . Applying a small anisotropic in - plane shear strain to the MEAF can block domain wall precession to improve reliability and speed of switching
Current-Driven Production Of Vortex-Antivortex Pairs In Planar Josephson Junction Arrays And Phase Cracks In Long-Range Order, Francisco Estellés-Duart, Miguel Ortuño, Andrés M. Somoza, Valerii M. Vinokur, Alex Gurevich
Current-Driven Production Of Vortex-Antivortex Pairs In Planar Josephson Junction Arrays And Phase Cracks In Long-Range Order, Francisco Estellés-Duart, Miguel Ortuño, Andrés M. Somoza, Valerii M. Vinokur, Alex Gurevich
Physics Faculty Publications
Proliferation of topological defects like vortices and dislocations plays a key role in the physics of systems with long-range order, particularly, superconductivity and superfluidity in thin films, plasticity of solids, and melting of atomic monolayers. Topological defects are characterized by their topological charge reflecting fundamental symmetries and conservation laws of the system. Conservation of topological charge manifests itself in extreme stability of static topological defects because destruction of a single defect requires overcoming a huge energy barrier proportional to the system size. However, the stability of driven topological defects remains largely unexplored. Here we address this issue and investigate numerically …
Tailoring The Asymmetric Magnetoimpedance Response In Exchange-Biased Ni - Fe Multilayers, Ufuk Kilic, Carolina Ross, Carlos Garcia
Tailoring The Asymmetric Magnetoimpedance Response In Exchange-Biased Ni - Fe Multilayers, Ufuk Kilic, Carolina Ross, Carlos Garcia
Ufuk Kilic
Aftershocks In Slowly Compressed Bulk Metallic Glasses: Experiments And Theory, Louis W. Mcfaul, Wendelin Wright, Xiaojun Gu, Jonathan T. Uhl, Karin A. Dahmen
Aftershocks In Slowly Compressed Bulk Metallic Glasses: Experiments And Theory, Louis W. Mcfaul, Wendelin Wright, Xiaojun Gu, Jonathan T. Uhl, Karin A. Dahmen
Faculty Journal Articles
We observe two distinct interevent time patterns in the slip avalanches of compressed bulk metallic glasses (BMGs). Small slip avalanches cluster together in time, but large slip avalanches recur roughly periodically. We compare the timing patterns of BMG slip avalanches with timing patterns of earthquakes and with the predictions of a mean-field model. The time clustering of small avalanches is similar to the known time clustering of earthquake foreshocks and aftershocks.
Modeling Recombination In Solar Cells, Paul Chery
Modeling Recombination In Solar Cells, Paul Chery
Macalester Journal of Physics and Astronomy
Solar cells are a competitive alternative to nonrenewable energy sources such as fossil fuels. However, the efficiency of these devices is limited by photogenerated carrier recombination. We use a finite difference numerical model to study recombination phenomena in the absorber layer of solar cells including alternate recombination models and the effects of spatial distribution of recombination centers. We compare the effect of using the constant lifetime approximation for recombination to the full Shockley-Read-Hall expression in Silicon solar cells and find that the constant lifetime approximation holds for high defect densities but not for high photon flux densities. Finally, we simulate …
Measuring The Double Layer Capacitance Of Electrolytes With Varied Concentrations, Geoffrey Rath
Measuring The Double Layer Capacitance Of Electrolytes With Varied Concentrations, Geoffrey Rath
Senior Theses
When electric potentials are applied from an electrolytic fluid to a metal, a double layer capacitor, Cdl, develops at the interface. The layer directly at the interface is called the Stern layer and has a thickness equal to roughly the size of the ions in the fluid. The next layer, the diffuse layer, arises from the gathering of like charges in the Stern layer. This layer is the distance needed for ionic charges to return to equilibrium. This distance, called the Debye length, λ, depends on the square root of the electrolyte concentration. To study the properties of …
Functionalized Nanoporous Carbon Scaffolds For Hydrogen Storage Applications, Christopher Carr
Functionalized Nanoporous Carbon Scaffolds For Hydrogen Storage Applications, Christopher Carr
Dissertations
Recent efforts have demonstrated confinement in porous scaffolds at the nanoscale can alter the hydrogen sorption properties of metal hydrides, though not to an extent feasible for use in onboard hydrogen storage applications, proposing the need for a method allowing further modifications. The work presented here explores how the functionalization of nanoporous carbon scaffold surfaces with heteroatoms can modify the hydrogen sorption properties of confined metal hydrides in relation to non-functionalized scaffolds (FS). Investigations of nanoconfined LiBH4and NaAlH4indicate functionalizing the carbon scaffold surface with nitrogen can shift the activation energy of hydrogen desorption in excess of …
Nanostructural Origin Of Semiconductivity And Large Magnetoresistance In Epitaxial Nico2O4/Al2O3 Thin Films, Congmian Zhen, Xiaozhe Zhang, Wengang Wei, Wenzhe Guo, Ankit Pant, Xiaoshan Xu, Jian Shen, Li Ma, Denglu Hou
Nanostructural Origin Of Semiconductivity And Large Magnetoresistance In Epitaxial Nico2O4/Al2O3 Thin Films, Congmian Zhen, Xiaozhe Zhang, Wengang Wei, Wenzhe Guo, Ankit Pant, Xiaoshan Xu, Jian Shen, Li Ma, Denglu Hou
Xiaoshan Xu Papers
Despite low resistivity (~1 mΩ cm), metallic electrical transport has not been commonly observed in inverse spinel NiCo2O4, except in certain epitaxial thin films. Previous studies have stressed the effect of valence mixing and the degree of spinel inversion on the electrical conduction of NiCo2O4 films. In this work, we studied the effect of nanostructural disorder by comparing the NiCo2O4 epitaxial films grown on MgAl2O4 (1 1 1) and on Al2O3 (0 0 1) substrates. Although the optimal growth conditions are similar for the …
Elevated Temperature Dependence Of The Anisotropic Visible-To-Ultraviolet Dielectric Function Of Monoclinic Β-Ga2o3, Alyssa Mock, Jeremy Vanderslice, Rafal Korlacki, John A. Woollam, Mathias Schubert
Elevated Temperature Dependence Of The Anisotropic Visible-To-Ultraviolet Dielectric Function Of Monoclinic Β-Ga2o3, Alyssa Mock, Jeremy Vanderslice, Rafal Korlacki, John A. Woollam, Mathias Schubert
Department of Electrical and Computer Engineering: Faculty Publications
We report on the temperature dependence of the dielectric tensor elements of n-type conductive β-Ga2O3 from 22 °C to 550 °C in the spectral range of 1.5 eV–6.4 eV. We present the temperature dependence of the excitonic and band-to-band transition energy parameters using a previously described eigendielectric summation approach [A. Mock et al., Phys. Rev. B 96, 245205 (2017)]. We utilize a Bose-Einstein analysis of the temperature dependence of the observed transition energies and reveal electron coupling with average phonon temperature in excellent agreement with the average over all longitudinal phonon plasmon coupled modes reported previously [M. …
Anisotropy And Phonon Modes From Analysis Of The Dielectric Function Tensor And The Inverse Dielectric Function Tensor Of Monoclinic Yttrium Orthosilicate, Alyssa Mock, Rafal Korlacki, Sean Knight, Mathias Schubert
Anisotropy And Phonon Modes From Analysis Of The Dielectric Function Tensor And The Inverse Dielectric Function Tensor Of Monoclinic Yttrium Orthosilicate, Alyssa Mock, Rafal Korlacki, Sean Knight, Mathias Schubert
Department of Electrical and Computer Engineering: Faculty Publications
We determine the frequency dependence of the four independent Cartesian tensor elements of the dielectric function for monoclinic symmetry Y2SiO5 using generalized spectroscopic ellipsometry from 40–1200 cm−1. Three different crystal cuts, each perpendicular to a principle axis, are investigated. We apply our recently described augmentation of lattice anharmonicity onto the eigendielectric displacement vector summation approach [A.Mock et al., Phys. Rev. B 95, 165202 (2017)], and we present and demonstrate the application of an eigendielectric displacement loss vector summation approach with anharmonic broadening. We obtain an excellent match between all measured and model-calculated dielectric …
Saw Assisted Domain Wall Motion In Co/Pt Multilayers, Westin Edrington, Uday Singh, Maya Abo Dominguez, James Rehwaldt Alexander, Rabindra Nepal, Shireen Adenwalla
Saw Assisted Domain Wall Motion In Co/Pt Multilayers, Westin Edrington, Uday Singh, Maya Abo Dominguez, James Rehwaldt Alexander, Rabindra Nepal, Shireen Adenwalla
Shireen Adenwalla Papers
The motion of domain walls in thin ferromagnetic films is of both fundamental and technological interest. In particular, the ability to use drivers other than magnetic fields to control the positions of domain walls could be exciting for memory applications. Here, we show that high frequency dynamic strain produced by surface acoustic waves is an efficient driver of magnetic domain walls in ferromagnetic films with perpendicular anisotropy. A standing surface acoustic wave of resonant frequency 96.6MHz increases the domain wall velocities in thin films of [Co/Pt]n by an order of magnitude compared to magnetic fields alone. This effect is highly …
Structural, Transport, And Topological Properties Induced At Complex-Oxide Hetero-Interfaces, Justin K. Thompson
Structural, Transport, And Topological Properties Induced At Complex-Oxide Hetero-Interfaces, Justin K. Thompson
Theses and Dissertations--Physics and Astronomy
Complex-oxides have seen an enormous amount of attention in the realm of Condensed Matter Physics and Materials Science/Engineering over the last several decades. Their ability to host a wide variety of novel physical properties has even caused them to be exploited commercially as dielectric, metallic and magnetic materials. Indeed, since the discovery of high temperature superconductivity in the “Cuprates” in the late 1980’s there has been an explosion of activity involving complex-oxides. Further, as the experimental techniques and equipment for fabricating thin films and heterostructures of these materials has improved over the last several decades, the search for new and …
Functionalized Nanoporous Carbon Scaffolds For Hydrogen Storage Applications, Christopher L. Carr
Functionalized Nanoporous Carbon Scaffolds For Hydrogen Storage Applications, Christopher L. Carr
Doctoral Dissertations
"Recent efforts have demonstrated confinement in porous scaffolds at the nanoscale can alter the hydrogen sorption properties of metal hydrides, though not to an extent feasible for use in onboard hydrogen storage applications, proposing the need for a method allowing further modifications. The work presented here explores how the functionalization of nanoporous carbon scaffold surfaces with heteroatoms can modify the hydrogen sorption properties of confined metal hydrides in relation to non-functionalized scaffolds (FS). Investigations of nanoconfined LiBH4 and NaAlH4 indicate functionalizing the carbon scaffold surface with nitrogen can shift the activation energy of hydrogen desorption in excess of …