Other Physics Commons^™

Controlling The Microstructure And Associated Magnetic Properties Of Ni0.2mn3.2ga0.6 Melt-Spun Ribbons By Annealing, Mahmud Khan, Ohud Alshammari, Balamurugan Balamurugan, Bhaskar Das, David J. Sellmyer, Ahmad Us Saleheen, Shane Stadler

Nebraska Center for Materials and Nanoscience: Faculty Publications

Here we report on the structural and magnetic properties of Ni_0.2Mn_3.2Ga_0.6 melt- spun ribbons. The as-spun ribbons were found to exhibit mixed cubic phases that transform to non-cubic structure upon annealing. Additionally, an amorphous phase was found to co-exist in all ribbons. The SEM images show that minor grain forma- tion occurs on the as-spun ribbons. However, the formation of extensive nano-grains was observed on the surfaces of the annealed ribbons. While the as-spun ribbons exhibit predominantly paramagnetic behavior, the ribbons annealed under various thermal conditions were found to be ferromagnetic with a Curie temperature …

Effect Of Fe Substitution On The Structural, Magnetic And Electron-Transport Properties Of Half-Metallic Co2tisi, Y. Jin, J. Waybright, P. Kharel, I. Tutic, J. Herran, P. Lukashev, S. Valloppilly, D. J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

The structural, magnetic and electron-transport properties of Co₂Ti_1-xFe_xSi (x = 0, 0.25, 0.5) ribbons prepared by arc-melting and melt-spinning were investi- gated. The rapidly quenched Co₂Ti_0.5Fe_0.5Si crystallized in the cubic L2₁ structure whereas Co₂Ti_0.75Fe_0.25Si and Co₂TiFe₀Si showed various degrees of B2-type disorder. At room temperature, all the samples are ferromagnetic, and the Curie tem- perature increased from 360 K for Co₂TiSi to about 800 K for Co₂Ti_0.5Fe_0.5Si. The measured …

Measurement Of The Integrated Stokes Parameters Of Zn 468 Nm Fluorescence Excited By Polarized-Electron Impact, Nathan B. Clayburn, Timothy J. Gay

Timothy J. Gay Publications

The integrated Stokes parameters P₁, P₂, and P₃ of Zn (4³P_0,1 – 5³S₁) fluorescence resulting from transversely-spin-polarized electron impact excitation of the Zn (4s5s)5³S₁ state have been measured. This work was motivated by similar studies reported several years ago, in which non-zero values of the integrated Stokes parameter P₂ between the threshold for the (4s5s)5³S₁ excitation and the first cascading (4s5p)5³P_J threshold were measured. We observe optical excitation functions in agreement with previous experimental and theoretical results, but …

Theoretical Approach To Electroresistance In Ferroelectric Tunnel Junctions, Sou-Chi Chang, Azad Naeemi, Dmitri E. Nikonov, Alexei Gruverman

Alexei Gruverman Publications

In this paper, a theoretical approach comprising the nonequilibrium Green’s function method for electronic transport and the Landau-Khalatnikov equation for electric polarization dynamics is presented to describe polarization-dependent tunneling electroresistance (TER) in ferroelectric tunnel junctions. Using appropriate contact, interface, and ferroelectric parameters, the measured current-voltage characteristic curves in both inorganic (Co/BaTiO₃/La_0.67Sr_0.33MnO₃) and organic (Au/PVDF/W) ferroelectric tunnel junctions can be well described by the proposed approach. Furthermore, under this theoretical framework, the controversy of opposite TER signs observed experimentally by different groups in Co/BaTiO₃/La_0.67Sr_0.33MnO₃ systems is …

Investigation Of The Microsoft Kinect V2 Sensor As A Multi-Purpose Device For A Radiation Oncology Clinic, Evan Asher Silverstein

Wayne State University Dissertations

For a radiation oncology clinic, the number of devices available to assist in the workflow for radiotherapy treatments are quite numerous. Processes such as patient verification, motion management, or respiratory motion tracking can all be improved upon by devices currently on the market. These three specific processes can directly impact patient safety and treatment efficacy and, as such, are important to track and quantify. Most products available will only provide a solution for one of these processes and may be outside the reach of a typical radiation oncology clinic due to difficult implementation and incorporation with already existing hardware. This …

Effect Of Disorder On The Magnetic And Electronic Structure Of A Prospective Spin-Gapless Semiconductor Mncrval, P. Kharel, J. Herran, P. Lukashev, Y. Jin, J. Waybright, S. Gilbert, B. Staten, P. Gray, S. Valloppilly, Y. Huh, D. J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

Recent discovery of a new class of materials, spin-gapless semiconductors (SGS), has attracted considerable attention in the last few years, primarily due to potential applications in the emerging field of spin-based electronics (spintronics). Here, we investigate structural, electronic, and magnetic properties of one potential SGS compound, MnCr-VAl, using various experimental and theoretical techniques. Our calculations show that this material exhibits ≈ 0.5 eV band gap for the majority-spin states, while for the minority-spin it is nearly gapless. The calculated magnetic moment for the com- pletely ordered structure is 2.9 μ_B/f.u., which is different from our experimentally measured value …

Tunneling Magnetoresistance Sensors With Different Coupled Free Layers, Yen-Fu Liu, Xiaolu Yin, Yi Yang, Dan Ewing, Paul J. De Rego, Sy-Hwang Liou

Nebraska Center for Materials and Nanoscience: Faculty Publications

Large differences of magnetic coercivity (HC), exchange coupling field (HE), and tun- neling magnetoresistance ratio (TMR) in magnetic tunnel junctions with different coupled free layers are discussed. We demonstrate that the magnetization behavior of the free layer is not only dominated by the interfacial barrier layer but also affected largely by the magnetic or non-magnetic coupled free layers. All these parameters are sensitively controlled by the magnetic nanostructure, which can be tuned also by the magnetic annealing process. The optimized sensors exhibit a large field sensitivity of up to 261%/mT in the region of the reversal synthetic ferri- magnet at …

Radiation Therapy Medical Physics Review – Delivery, Interactions, Safety, Feasibility, And Head To Head Comparisons Of The Leading Radiation Therapy Techniques, Cielle Collins

Honors Theses and Capstones

Radiation therapy uses high energy radiation to kill cancer cells. Radiation therapy for cancer treatment can take the form of photon therapy (using x-rays and gamma rays), or charged particle therapy including proton therapy and electron therapy. Within these categories, numerous methods of delivery have been developed. For example, a certain type of radiation can be administered by a machine outside of the body, called external-beam radiation therapy, or by a “seed” placed inside of the body near cancer cells, called internal radiation therapy or brachytherapy. Approximately half of all cancer patients receive radiation therapy, and the form of radiation …

Nonlinear Dynamic Studies Of Pattern-Forming And Biomedical Systems, Doaa Taha

Wayne State University Dissertations

Nonlinear phenomena are ubiquitous in nature and in almost every discipline of science. Various nonlinear dynamic theories are being developed to investigate a wide range of complex nonlinear systems. In this work, we study two types of nonlinear phenomena. The first type involves understanding and controlling the properties and dynamics of two-dimensional (2D) material systems. We develop a binary phase field crystal (PFC) model which simultaneously addresses diffusive dynamics of large-scale systems and resolves material microstructures, and apply the model to the study of two material systems. (1) We use this PFC model to investigate the self assembly of 2D …

Hidden Symmetries In String Theory, Iurii Chervonyi

Legacy Theses & Dissertations (2009 - 2024)

In this thesis we study hidden symmetries within the framework of string theory. Symmetries play a very important role in physics: they lead to drastic simplifications, which allow one to compute various physical quantities without relying on perturbative techniques.

Gravitational Microlensing, Wesley M. Barnes

Theses and Dissertations

A gravitational microlensing event occurs when a foreground star passes near our line of site to a background source star. The foreground star acts as a lens, perturbing the image of the source star and amplifying the apparent intensity. Because the lens is in motion relative to the source star, the amplification is a function in time, resulting in a characteristic microlensing light curve. If the lens happens to have a planetary companion, the resulting light curve will be perturbed due the planet and the characteristics of the binary system can be ascertained.

Question 1: Time Texting; Question 2: Opening Doors, Larry Weinstein

Physics Faculty Publications

[Introduction] How much total time do Americans spend texting every year?

Can a typical human open a 20-ton door (swinging on hinges around a vertical axis like a normal room door) with no mechanical assistance?

Interferometric Measurement Of The Index Of Refraction Of Liquids, Clay Huskey

Summer Community of Scholars Posters (RCEU and HCR Combined Programs)

No abstract provided.

Gamma/Hadron Separation For The Hawc Observatory, Michael J. Gerhardt

Dissertations, Master's Theses and Master's Reports

The High-Altitude Water Cherenkov (HAWC) Observatory is a gamma-ray observatory sensitive to gamma rays from 100 GeV to 100 TeV with an instantaneous field of view of ~2 sr. It is located on the Sierra Negra plateau in Mexico at an elevation of 4,100 m and began full operation in March 2015. The purpose of the detector is to study relativistic particles that are produced by interstellar and intergalactic objects such as: pulsars, supernova remnants, molecular clouds, black holes and more. To achieve optimal angular resolution, energy reconstruction and cosmic ray background suppression for the extensive air showers detected by …

Comment On “Electronic Structure Of Mo(1−X)Rex Alloys Studied Through Resonant Photoemission Spectroscopy”, Prescott Evans, Peter A. Dowben

Peter Dowben Publications

Further analysis of the resonant photoemission data, found within Sundar et al (2016 J. Phys.: Condens. Matter 28 315502), show the intensities do not follow the elemental composition in the Mo_1−xRe_x alloy. Similar trends are observed in the published data for Gd_1−xNi_x alloy films. The analysis of the resonant photoemission intensities suggests that Mo in the Mo_1−xRe_x alloy and Gd in the Gd_1−xNi_x alloy have nearest neighbor bonds to Re and Ni respectively. This means the A–B bond is favored over the average of …

Anomalous Photovoltaic Effect In Organic-Inorganic Hybrid Perovskite Solar Cells, Yongbo Yuan, Tao Li, Qi Wang, Jie Xing, Alexei Gruverman, Jinsong Huang

Alexei Gruverman Publications

Organic-inorganic hybrid perovskites (OIHPs) have been demonstrated to be highly successful photovoltaic materials yielding very-high-efficiency solar cells. We report the room temperature observation of an anomalous photovoltaic (APV) effect in lateral structure OIHP devices manifested by the device’s open-circuit voltage (V_OC) that is much larger than the bandgap of OIHPs. The persistent V_OC is proportional to the electrode spacing, resembling that of ferroelectric photovoltaic devices. However, the APV effect in OIHP devices is not caused by ferroelectricity. The APV effect can be explained by the formation of tunneling junctions randomly dispersed in the polycrystalline films, which allows …

Domain Formation Mechanism Of The Si(110) “16 × 2” Reconstruction, N. K. Lewis, Nathan B. Clayburn, Evan M. Brunkow, Timothy J. Gay, Y. Lassailly, J. Fujii, I. Vobornik, W. R. Flavell, E. A. Seddon

Timothy J. Gay Publications

The main factor that determines which of the two domains forms upon reconstruction of the Si(110) “16 × 2” surface has been investigated. Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) images showed that the domain orientation was independent of the heating current direction used to induce the Si(110) “16 × 2” reconstruction. Reciprocal-space lattice models of the reconstruction allowed for the correct identification of domain orientations in the LEED images, and they confirmed that the reconstruction is two dimensionally chiral. It is proposed that the domain orientation upon surface reconstruction is determined by the direction of monatomic steps …

Ch3Nh3Pbi3 Perovskites: Ferroelasticity Revealed, Evgheni Strelcov, Qingfeng Dong, Tao Li, Jungseok Chae, Yuchuan Shao, Yehao Deng, Alexei Gruverman, Jinsong Huang, Andrea Centrone

Alexei Gruverman Publications

Ferroelectricity has been proposed as a plausible mechanism to explain the high photovoltaic conversion efficiency in organic-inorganic perovskites; however, convincing experimental evidence in support of this hypothesis is still missing. Identifying and distinguishing ferroelectricity from other properties, such as piezoelectricity, ferroelasticity, etc., is typically nontrivial because these phenomena can coexist in many materials. In this work, a combination of microscopic and nanoscale techniques provides solid evidence for the existence of ferroelastic domains in both CH₃NH₃PbI₃ polycrystalline films and single crystals in the pristine state and under applied stress. Experiments show that the configuration of CH …

Saving The Physics Ii: Who Needs To Be Saved? It Depends On Your Metaphysics, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

Physics does not need to be saved. If anything, physics was rescued in the early twentieth century with the advancement of both the theories of relativity and quantum mechanics. What needs to be saved is our world outlook or metaphysics because how a society acts and develops depends on what its belief systems are. Here we explore how a new metaphysics where consciousness is fundamental might just be what modern societies need.

Review Of Qbism: The Future Of Quantum Physics, Matthew S. Leifer

Mathematics, Physics, and Computer Science Faculty Articles and Research

A review of QBism: The Future of Quantum Physics by Hans Christian von Baeyer.

Application Of The Fisher Dimer Model To Dna Condensation, John C. Baker Iii

Theses and Dissertations

This paper considers the statistical mechanics occupation of the edge of a single helix of DNA by simple polymers. Using Fisher's exact closed form solution for dimers on a two-dimensional lattice, a one-dimensional lattice is created mathematically that is occupied by dimers, monomers, and holes. The free energy, entropy, average occupation, and total charge on the lattice are found through the usual statistical methods. The results demonstrate the charge inversion required for a DNA helix to undergo DNA condensation.