Effect Of Structural Disorder On Magnetic Properties Of Mncrval,
2017
University of Northern Iowa
Effect Of Structural Disorder On Magnetic Properties Of Mncrval, Juliana Herran, Rishabh Dalal, Paul Gray, Pavel Lukashev
Research in the Capitol
Operation of virtually any modern electronic device relies on magnetic materials. In particular, these materials are the cornerstone of data storage and processing in computer hardware elements, such as hard drives and random access memories. Here, we theoretically study an interplay between structural and magnetic properties of MnCrVAl, a material which recently attracted significant attention due to its rather exotic electronic structure. In particular, this material behaves either as an insulator or as a metal, depending on which “spin” (an intrinsic property of any fundamental particle) of the electron is considered. Using advanced computer simulation techniques (density functional calculations on …
Tio2 Coating Method For Nanocellulose Aerogel,
2017
University of Northern Iowa
Tio2 Coating Method For Nanocellulose Aerogel, Byron Fritch, Tim Kidd
Research in the Capitol
Titanium dioxide has been shown to be an effective catalyst for splitting water into hydrogen and oxygen gas. By increasing the surface area of the titanium dioxide catalyst, the rate of water splitting may increase. A possible method to increase the splitting of water uses a high surface area composite material formed by coating nanocellulose aerogels with titanium dioxide. Different coating methods were studied using titanium isopropoxide as the titanium dioxide source to create such composites. It was found that the most consistent titanium dioxide coatings were formed during a 12 hour titanium isopropoxide vapor bath. Other coating methods collapsed …
Enhancing High-Order-Harmonic Generation By Time Delays Between Two-Color, Few-Cycle Pulses,
2017
University of Nebraska - Lincoln
Enhancing High-Order-Harmonic Generation By Time Delays Between Two-Color, Few-Cycle Pulses, Dian Peng, Liang-Wen Pi, M. V. Frolov, Anthony F. Starace
Anthony F. Starace Publications
Use of time delays in high-order-harmonic generation (HHG) driven by intense two-color, few-cycle pulses is investigated in order to determine means of optimizing HHG intensities and plateau cutoff energies. Based upon numerical solutions of the time-dependent Schrõdinger equation for the H atom as well as analytical analyses, we show that introducing a time delay between the two-color, few-cycle pulses can result in an enhancement of the intensity of the HHG spectrum by an order of magnitude (or more) at the cost of a reduction in the HHG plateau cutoff energy. Results for both positive and negative time delays as well …
Effect Of Disorder On The Resistivity Of Cofecral Films,
2017
University of Nebraska-Lincoln
Effect Of Disorder On The Resistivity Of Cofecral Films, Y. Jin, R. Skomski, P. Kharel, S.R. Valloppilly, D. J. Sellmyer
Nebraska Center for Materials and Nanoscience: Faculty Publications
Structural and electron-transport properties of thin films of the ferrimagnetic Heusler compound CoFeCrAl have been investigated to elucidate structure-property relationships. The alloy is, ideally, a spin-gapless semiconductor, but structural disorder destroys the spin-gapless character and drastically alters the transport behavior. Two types of CoFeCrAl films were grown by magnetron sputtering deposition at 973 K, namely polycrystalline films on Si substrates and epitaxial films on MgO (001) substrates. The resistivity decreases with increasing temperature, with relatively small temperature coefficients of –0.19 cm=K for the polycrystalline films and –0.12 cm=K for the epitaxial films. The residual resistivity of the polycrystalline films deposited …
Designing Novel Nanostructured Permanent Magnets,
2017
University of Nebraska at Omaha
Designing Novel Nanostructured Permanent Magnets, Ali Al Kadhim
UNO Student Research and Creative Activity Fair
Rare earth element based alloys have been the source of high performance magnetic alloys, and have played a paramount role in the development of various technologies, including: memory devices (such as credit cards, random-access memory), sensors, and various biomedical applications. However, there is a tremendous need to replace rare earth metals with material with powerful magnetic properties. Our group recently found CrTe-based materials that show very promising magnetic properties in nanostructured form. The magnetic modeling of such material in nanostructured form prior to their fabrication demonstrates their magnetic properties in bulk form. In this project, we investigate the behavior of …
Improving Sers-Based Readout Strategy For Biomarker Detecting Immunoassays,
2017
U.N.O. Physics Department
Improving Sers-Based Readout Strategy For Biomarker Detecting Immunoassays, Joseph Smolsky
UNO Student Research and Creative Activity Fair
Detection and monitoring of disease biomarkers increases probability of successful disease treatment. Surface enhanced Raman scattering (SERS) has several advantages over conventional readout strategies utilized in detecting immunoassays. SERS provides a method for chemical characterization based on molecular vibrational spectra. Raman signals are typically weak and need to be enhanced. This can be done using plasmons in nanoparticles of noble metals, we use gold (Au). Molecules with known spectra, Raman reporter molecules (RRM), can be adsorbed to Au nanoparticles. This enhances the Raman signal of the RRM when illuminated by a laser of optimal wavelength. Adding antibodies to nanoparticles modified …
Synthesis And Characterization Of The 2-Dimensional Transition Metal Dichalcogenides,
2017
Portland State University
Synthesis And Characterization Of The 2-Dimensional Transition Metal Dichalcogenides, Robert Browning
Dissertations and Theses
In the last 50 years, the semiconductor industry has been scaling the silicon transistor to achieve faster devices, lower power consumption, and improve device performance. Transistor gate dimensions have become so small that short channel effects and gate leakage have become a significant problem. To address these issues, performance enhancement techniques such as strained silicon are used to improve mobility, while new high-k gate dielectric materials replace silicon oxide to reduce gate leakage. At some point the fundamental limit of silicon will be reached and the semiconductor industry will need to find an alternate solution. The advent of graphene led …
Index Of Refraction From The Near-Ultraviolet To The Near-Infrared From A Single Crystal Microwave-Assisted Cvd Diamond,
2017
Embry-Riddle Aeronautical University
Index Of Refraction From The Near-Ultraviolet To The Near-Infrared From A Single Crystal Microwave-Assisted Cvd Diamond, Giorgio Turri, Scott Webster, Ying Chen, Benjamin Wickham, Andrew Bennett, Michael Bass
Publications
The refractive index of a type IIa CVD-grown single-crystal diamond was measured by ellipsometry from the near ultraviolet to the near infrared region of the spectrum. As a consequence, a one term Sellmeier Equation with coefficents of B-1 = 4.658 and C-1 = 112.5 for the refractive index of diamond, for the wavelength range from 300 to 1650 nm, was derived that is only as accurate as the input data, +/- 0.002. The experimental results in this paper between 800 and 1650 nm are new, adding to the values available in the literature.
Developing An Imaging System To Monitor Atom Traps For Neutral Atom Quantum Computing,
2017
California Polytechnic State University, San Luis Obispo
Developing An Imaging System To Monitor Atom Traps For Neutral Atom Quantum Computing, Jenna Valdez
Physics
Quantum computing exploits the laws of quantum mechanics to exponentially increase computing rate for certain processes. A realized quantum computer could break encryptions and simulate large quantum systems previously unbreakable and unattainable with classical computers. Neutral atom quantum computing is a viable candidate for building these devices that satisfies four of the five criteria for a successful quantum computer. We are exploring a novel method in creating neutral atom qubits that involves a magneto-optical trap and a dipole trap created in the diffraction pattern behind an array of pinholes. The magneto-optical trap works to cool the atoms and centralize them …
Half-Metallic Magnetism In Ti3co5-Xfexb2,
2017
Indian Institute of Technology
Half-Metallic Magnetism In Ti3co5-Xfexb2, Rohit Pathak, Imran Ahamed, W. Y. Zhang, Shah Vallopilly, D. J. Sellmyer, Ralph Skomski, Arti Kashyap
Nebraska Center for Materials and Nanoscience: Faculty Publications
Bulk alloys and thin films of Fe-substituted Ti3Co5B2 have been investigated by first-principle density-functional calculations. The series, which is of interest in the context of alnico magnetism and spin electronics, has been experimentally realized in nanostructures but not in the bulk. Our bulk calculations predict paramagnetism for Ti3Co5B2, Ti3Co4FeB2 and Ti3CoFe4B2, whereas Ti3Fe5B2 is predicted to be ferromagnetic. The thin films are all ferromagnetic, indicating that moment formation may be facilitated at nanostructural …
Cooperative And Noncooperative Magnetization Reversal In Alnicos,
2017
University of Nebraska - Lincoln
Cooperative And Noncooperative Magnetization Reversal In Alnicos, Raplh Skomski, Liqin Ke, Matthew J. Kramer, Iver E. Anderson, C.Z. Wang, W.Y. Zhang, Jeff E. Shield, D. J. Sellmyer
Nebraska Center for Materials and Nanoscience: Faculty Publications
It is investigated how magnetostatic interactions affect the coercivity of alnicotype magnets. Starting from exact micromagnetic relations, we analyze two limits, namely cooperative reversal processes operative on short lengths scales and noncooperative reversal processes on long length scales. In alnicos, intrawire interactions are predominantly cooperative, whereas interwire effects are typically noncooperative. However, the transition between the regimes depends on feature size and hysteresis-loop shape, and interwire cooperative effects are largest for nearly rectangular loops. Our analysis revises the common shape-anisotropy interpretation of alnicos.
Two-Color Multiphoton Emission From Nanotips,
2017
Texas A & M University - College Station
Two-Color Multiphoton Emission From Nanotips, Wayne Cheng-Wei Huang, Maria Becker, Joshua Beck, Herman Batelaan
Department of Physics and Astronomy: Faculty Publications
Two-color multiphoton emission from polycrystalline tungsten nanotips has been demonstrated using two-color laser fields. The two-color photoemission is assisted by a three-photon multicolor quantum channel, which leads to a twofold increase in quantum efficiency. Weak-field control of two- color multiphoton emission was achieved by changing the efficiency of the quantum channel with pulse delay. The result of this study complements two-color tunneling photoemission in strong fields, and has potential applications for nanowire-based photonic devices. Moreover, the demonstrated two-color multiphoton emission may be important for realizing ultrafast spin-polarized electron sources via optically injected spin current.
Phonon Interference In Crystalline And Amorphous Confined Nanoscopic Films,
2017
Marshall University
Phonon Interference In Crystalline And Amorphous Confined Nanoscopic Films, Zhi Liang, Thomas E. Wilson, Pawel Keblinski
Physics Faculty Research
Using molecular dynamics phonon wave packet simulations, we study phonon transmission across hexagonal (h)-BN and amorphous silica (a-SiO2) nanoscopic thin films sandwiched by two crystalline leads. Due to the phonon interference effect, the frequency-dependent phonon transmission coefficient in the case of the crystalline film (Si|h-BN|Al heterostructure) exhibits a strongly oscillatory behavior. In the case of the amorphous film (Si|a-SiO2|Al and Si|a-SiO2|Si heterostructures), in spite of structural disorder, the phonon transmission coefficient also exhibits oscillatory behavior at low frequencies (up to ∼1.2 THz), with a period of oscillation consistent with the …
Second Harmonic Generation – A Novel Approach In Retinal Imaging,
2017
CUNY Graduate Center
Second Harmonic Generation – A Novel Approach In Retinal Imaging, Denis Y. Sharoukhov
Dissertations, Theses, and Capstone Projects
Here we present the utilization of Second Harmonic Generation (SHG) for label-free imaging of microtubules (MTs) in the retinal nerve fiber layer (RNFL). MTs are an important part of axonal cytoskeleton, providing structural support and serving as a railroad in intracellular transport. We demonstrate the application of SHG microscopy to the following studies: 1) Can changes in MT conformation be detected when treated with a stabilizing drug (Taxol); 2) if disruption in MT precedes loss of axons in a mouse model of glaucoma (DBA/2J); and 3) if elevated levels of intraocular pressure affect MT integrity. Our results validate SHG imaging …
Epitaxial Strain Controlled Magnetocrystalline Anisotropy In Ultrathin Ferh/Mgo Bilayers,
2017
Tongji University & California State University
Epitaxial Strain Controlled Magnetocrystalline Anisotropy In Ultrathin Ferh/Mgo Bilayers, Guohul Zheng, San-Huang Ke, Maosheng Miao, Jinwoong Kim, R, Ramesh, Nicholas Kioussis
Nebraska Center for Materials and Nanoscience: Faculty Publications
Using ab initio electronic structure calculations we have investigated the effect of epitazial strain on the magnetocrystalline anisotropy (MCA) of ultrathin FeRh/MgO heterostructures. Analysis of the energy- and k-resolved distribution of the orbital character of the band structure reveals that MCA largely arises from the spin-orbit coupling (SOC) between dx2-y2 and dxz/dyz orbitlas of Fe atoms at the FeRh/MhO interface. We demonstrate that the strain has significant effects on the MCA: It not only affects the value of the MCA but also induces a switching of the magnetic easy axis from perpendicular on in-plane direction. The …
First-Principle Investigation Of Structural, Electronic And Magnetic Properties Of Co2vin And Covin Heusler Compounds,
2017
University of Nairobi
First-Principle Investigation Of Structural, Electronic And Magnetic Properties Of Co2vin And Covin Heusler Compounds, Zipporah Muthui, Rohit Pathak, Robinson Musembi, Julius Mwabora, Ralph Skomski, Arti Kashyap
Nebraska Center for Materials and Nanoscience: Faculty Publications
Investigation of the structural, electronic and magnetic properties of full-Heusler Co2VIn as well as half-Heusler CoVIn Cobalt based Heusler compounds using density functional theory (DFT) leads to the general conclusion that Co2VIn and CoVIn are half-metallic materials with a gap at the Fermi level in the minority states and majority states respectively. A Hubbard-like Coulomb correlation term U has been included in the DFT (DFT+U) for the computation of the electronic and magnetic properties of the compounds. The structural properties have been calculated for the paramagnetic and ferromagnetic phases, and both Co2VIn …
Controlling The Microstructure And Associated Magnetic Properties Of Ni0.2mn3.2ga0.6 Melt-Spun Ribbons By
Annealing,
2017
Miami University - Oxford
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 Ni0.2Mn3.2Ga0.6 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,
2017
University of Nebraska - Lincoln
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 Co2Ti1-xFexSi (x = 0, 0.25, 0.5) ribbons prepared by arc-melting and melt-spinning were investi- gated. The rapidly quenched Co2Ti0.5Fe0.5Si crystallized in the cubic L21 structure whereas Co2Ti0.75Fe0.25Si 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 Co2Ti0.5Fe0.5Si. The measured …
Laser-Assisted Nanowelding Of Graphene To Metals: An Optical Approach Toward Ultralow
Contact Resistance,
2017
University of Nebraska-Lincoln
Laser-Assisted Nanowelding Of Graphene To Metals: An Optical Approach Toward Ultralow Contact Resistance, K. Keramatnejad, Yunshen Zhou, Da Wei Li, Hossein Rabiee Golgir, Xi Huang, Qi Ming Zhou, Jingfeng Song, Stephen Ducharme, Yongfeng Lu
Stephen Ducharme Publications
The electrical performance of graphene-based devices is largely limited by substantial contact resistance at the heterodimensional graphene-metal junctions. A laserassisted nanowelding technique was developed to reduce graphene-metal (G-M) contact resistance and improve carrier injection in suspended graphene devices. Selective breakdown of C-C bonds and formation of structural defects were realized through laser irradiation at the edges of graphene within the G-M contact regions in order to increase the chemical reactivity of graphene, facilitate G-M bonding and, therefore, maximize interfacial carrier transportation. Through this method, significantly reduced G-M contact resistances, as low as 2.57 Ω-μm were obtained. In addition, it was …
Measurement Of The Integrated Stokes Parameters Of Zn 468
Nm Fluorescence Excited By Polarized-Electron Impact,
2017
University of Nebraska - Lincoln
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 (43P0,1 – 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)53PJ threshold were measured. We observe optical excitation functions in agreement with previous experimental and theoretical results, but …
