Structural And Electronic Origin Of The Magnetic Structures In Hexagonal Lufeo3,
2014
Temple University
Structural And Electronic Origin Of The Magnetic Structures In Hexagonal Lufeo3, Hongwei Wang, Igor V. Solovyev, Wenbin Wang, Xiao Wang, Philip J. Ryan, David J. Keavney, Jong-Woo Kim, Thomas Z. Ward, Leyi Zhu, Jian Shen, X. M. Cheng, Lixin He, Xiaoshan Xu, Xifan Wu
Xiaoshan Xu Papers
Using combined theoretical and experimental approaches, we studied the structural and electronic origin of the magnetic structure in hexagonal LuFeO3. Besides showing the strong exchange coupling that is consistent with the high magnetic ordering temperature, the previously observed spin reorientation transition is explained by the theoretically calculated magnetic phase diagram. The structural origin of this spin reorientation that is responsible for the appearance of spontaneous magnetization, is identified by theory and verified by x-ray diffraction and absorption experiments.
The Ferroelectricity At The Nanoscale,
2014
Institute of Crystallography, Russian Academy of Sciences, Moscow
The Ferroelectricity At The Nanoscale, Vladimir M. Fridkin, Stephen Ducharme
Stephen Ducharme Publications
The review of ferroelectric properties at the nanoscale is presented. Determining the nanoscale, authors bear in mind the film thickness equal by the order of value to the size of critical domain nucleus. Three phenomena are considered: ferroelectric switching, scaling of coercive field and bulk photovoltaic effect. The investigation of ferroelectricity at the nanoscale started 20 years ago. The nanoscaled ferroelectricics with perovskite structure came to be considered only the last few years.
Nanoscale Thermoelectrics: A Study Of The Absolute Seebeck Coefficient Of Thin Films,
2014
University of Denver
Nanoscale Thermoelectrics: A Study Of The Absolute Seebeck Coefficient Of Thin Films, Sarah J. Mason
Electronic Theses and Dissertations
The worlds demand for energy is ever increasing. Likewise, the environmental impact of climate change due generating that energy through combustion of fossil fuels is increasingly alarming. Due to these factors new sources of renewable energies are constantly being sought out. Thermoelectric devices have the ability to generate clean, renewable, energy out of waste heat. However promising that is, their inefficiency severely inhibits applicability and practical use. The usefulness of a thermoelectric material increases with the dimensionless quantity, ZT, where, Z = S2σ/κ, and S, σ, and κ are the Seebeck coefficient and electrical and thermal …
Ferroelectric Switching In Epitaxial Gete Films,
2014
National Institute of Advanced Industrial Science and Technology (AIST), Japan
Ferroelectric Switching In Epitaxial Gete Films, A. V. Kolobov, D. J. Kim, A. Giussani, P. Fons, J. Tominaga, R. Calarco, Alexei Gruverman
Alexei Gruverman Publications
In this paper, using a resonance-enhanced piezoresponse force microscopy approach supported by density functional theory computer simulations, we have demonstrated the ferroelectric switching in epitaxial GeTe films. It has been shown that in films with thickness on the order of several nanometers reversible reorientation of polarization occurs due to swapping of the shorter and longer Ge-Te bonds in the interior of the material. It is also hinted that for ultra thin films consisting of just several atomic layers weakly bonded to the substrate, ferroelectric switching may proceed through exchange of Ge and Te planes within individual GeTe layers.
Comparison Of The Sharpness Of Tungsten Field Emission Tips From Traditional Electrical Characterization To Tip Geometries Imaged By Scanning Electron Microscopy,
2014
Hamline University
Comparison Of The Sharpness Of Tungsten Field Emission Tips From Traditional Electrical Characterization To Tip Geometries Imaged By Scanning Electron Microscopy, Emma C. Reeves
Departmental Honors Projects
Using field emission data obtained from 11 etched Tungsten successful field emission tips of radius about 20 to 100 nanometers, FN type linear models were compared. The emission tip radii were determined using an iteration method derived from the modified FN linear equation. In addition, Scanning Electron Microscopy images of 5 successful emitters were obtained. These images were fit to a circular model to estimate the actual radius and compared to empirically predicted radius values. A hyperbolic model was further fit to the images and the circle of similar apex curvature was derived. A method for calculating the electric field …
Nanostrucured Lithium Iron Phosphate As Cathode Material For Lithium Ion-Batteries,
2014
Wayne State University
Nanostrucured Lithium Iron Phosphate As Cathode Material For Lithium Ion-Batteries, Khadije Bazzi
Wayne State University Dissertations
Lithium-ion batteries are the power source of choice for portable electronics, power tools and electric-based transportation. This outstanding commercial success has spawned great international interest in applying this technology to systems that demand higher power, such as the electric component of hybrid, extended range, and electric vehicles. This would require new electrode materials that are less expensive, more energetic, and more environmentally friendly than the present ones. Of particular interest is the olivine-structured LiFePO4 cathode developed by Goodenough and co-workers, which offers several appealing features, such as a high, flat voltage profile and relatively high theoretical specific capacity (170 mAhg−1), …
Multiferroic Hexagonal Ferrites (H-Rfeo3, R=Y, Dy-Lu): An
Experimental Review,
2014
University of Nebraska-Lincoln
Multiferroic Hexagonal Ferrites (H-Rfeo3, R=Y, Dy-Lu): An Experimental Review, Xiaoshan Xu, Wenbin Wang
Xiaoshan Xu Papers
Hexagonal ferrites (h-RFeO3, R=Y, Dy-Lu) have recently been identified as a new family of multiferroic complex oxides. The coexisting spontaneous electric and magnetic polarizations make h-RFeO3 rare-case ferroelectric ferromagnets at low temperature. Plus the room-temperature mul- tiferroicity and predicted magnetoelectric effect, h-RFeO3 are promising materials for multiferroic applications. Here we review the structural, ferroelectric, magnetic, and magnetoelectric properties of h-RFeO3. The thin film growth is also discussed because it is critical in making high quality single crystalline materials for studying intrinsic properties.
Laboratory Manual For Physics Of Lasers And Modern Optics, 13th Ed,
2014
University of Nebraska - Lincoln
Laboratory Manual For Physics Of Lasers And Modern Optics, 13th Ed, Stephen Ducharme
Stephen Ducharme Publications
You will encounter challenging puzzles and explore new and exciting physical phenomena. You will be provided with sufficient tools, guidance and other resources, but what you learn depends on your inquisitiveness and creativity. This laboratory course is designed to serve two purposes: 1) To explore a variety of physical principles using the fascinating and diverse behavior of light. 2) To learn some of the principles behind the pervasive and expanding area of optical and laser technology. This course is suitable for students of science, life sciences, and engineering, or any student who is curious about light. The prerequisites are the …
Spin Density Waves In Periodically Strained
Graphene Nanoribbons,
2014
University of Nebraska at Omaha
Spin Density Waves In Periodically Strained Graphene Nanoribbons, Nabil M. Al-Aqtash, Renat F. Sabirianov
Nebraska Center for Materials and Nanoscience: Faculty Publications
Zigzag graphene nanoribbons (ZGNRs) are antiferromagnetic in the ground state with zero net magnetization due to the compensation of contributions from opposite edges. Uniform deformations (both shear and axial) do not produce magnetization due to symmetry restrictions. However, we report the results of first-principles calculations that predict the induction of spin density waves (SDWs) in ZGNRs under non-uniform periodic strain. Using the density functional theory (DFT) method, we show that a sinusoidal magnetization variation along the axis of the ribbon occurs under a sinusoidal transversal shear strain. SDWs appear due to the presence of a strain gradient that induced asymmetry …
Effective Thermoelectric Power Generation In An Insulated Compartment,
2014
James Madison University
Effective Thermoelectric Power Generation In An Insulated Compartment, Harkirat S. Mann, Yosep Schwab, Brian N. Lang, Jarrett L. Lancaster, Ronald J. Parise, Giovanna Scarel
Department of Physics and Astronomy - Faculty Scholarship
The Seebeck coefficient S is a temperature- and material-dependent property, which linearly and causally relates the temperature difference ΔT between the “hot” and “cold” junctions of a thermoelectric power generator (TEC-PG) to the voltage difference ΔV . This phenomenon is the Seebeck effect (SE), and can be used to convert waste heat into usable energy. This work investigates the trends of the effective voltage output ΔV (t ) and effective Seebeck coefficient S′(t ) versus several hours of activity of a solid state TEC-PG device. The effective Seebeck coefficient S′(t ) here …
Electronic Structure And Charge Transfer Excited States Of Endohedral Fullerene Containing Electron Donor-Acceptor Complexes Utilized In Organic Photovoltaics,
2014
University of Texas at El Paso
Electronic Structure And Charge Transfer Excited States Of Endohedral Fullerene Containing Electron Donor-Acceptor Complexes Utilized In Organic Photovoltaics, Fatemeh Amerikheirabadi
Open Access Theses & Dissertations
Organic Donor &ndash Acceptor complexes form the main component of the organic photovoltaic devices (OPVs). The open circuit voltage of OPVs is directly related to the charge transfer excited state energies of these complexes. Currently a large number of different molecular complexes are being tested for their efficiency in photovoltaic devices. In this work, density functional theory as implemented in the NRLMOL code is used to investigate the electronic structure and related properties of these donor &ndash acceptor complexes. The charge transfer excitation energies are calculated using the perturbative delta self &ndash consistent field method recently developed in our group …
Quantum Non-Locality Vs. Quasi-Local Measurement In The Conditions Of The Aharonov-Bohm Effect,
2014
Chapman University
Quantum Non-Locality Vs. Quasi-Local Measurement In The Conditions Of The Aharonov-Bohm Effect, Armen Gulian
Mathematics, Physics, and Computer Science Faculty Articles and Research
Theoretical explanation of the Meissner effect involves proportionality between current density and vector potential, which has many deep consequences. As noticed by de Gennes, superconductors in a magnetic field "find an equilibrium state where the sum of kinetic and magnetic energies is minimum" and this state "corresponds to the expulsion of the magnetic field". This statement still leaves an open question: from which source is the superconducting current acquiring its kinetic energy? A naïve answer, perhaps, is from the energy of the magnetic field. However, one can consider situations (Aharonov-Bohm effect), where the classical magnetic field is locally absent in …
Skyrmionic Spin Seebeck Effect Via Dissipative Thermomagnonic Torques,
2014
University of Nebraska - Lncoln
Skyrmionic Spin Seebeck Effect Via Dissipative Thermomagnonic Torques, Alexey Kovalev
Department of Physics and Astronomy: Faculty Publications
We derive thermomagnonic torque and its “β-type” dissipative correction from the stochastic Landau-Lifshitz-Gilbert equation. The β-type dissipative correction describes viscous coupling between magnetic dynamics and magnonic current and it stems from spin mistracking of the magnetic order. We show that thermomagnonic torque is important for describing temperature gradient induced motion of skyrmions in helical magnets while dissipative correction plays an essential role in generating transverse Magnus force. We propose to detect such skyrmionic motion by employing the transverse spin Seebeck effect geometry.
Demonstrating Entanglement By Testing Bell's Theorem In Majorana Wires,
2014
University of California, Riverside
Demonstrating Entanglement By Testing Bell's Theorem In Majorana Wires, David E. Drummond, Alexey Kovalev, Chang-Yu Hou, Kirill Shtengel, Leonid P. Pryadko
Department of Physics and Astronomy: Faculty Publications
We propose an experiment that would establish the entanglement of Majorana zero modes in semiconductor nanowires by testing the Bell and Clauser-Horne-Shimony-Holt inequalities. Our proposal is viable with realistic system parameters, simple “keyboard” gating, and projective measurement. Theoretical models and simulation results indicate entanglement can be demonstrated with moderately accurate gate operations. In addition to providing further evidence for the existence of the Majorana bound states, our proposal could be used as an experimental stepping stone to more complicated braiding experiments.
Active Control Of Magnetoresistance Of Organic
Spin Valves Using Ferroelectricity,
2014
Fudan University
Active Control Of Magnetoresistance Of Organic Spin Valves Using Ferroelectricity, Dali Sun, Mei Fang, Xiaoshan Xu, Lu Jiang, Hangwen Guo, Yanmei Wang, Wenting Yang, Lifeng Yin, Paul C. Snijders, T. Z. Ward, Zheng Gai, X. -G. Zhang, Ho Nyung Lee, Jian Shen
Xiaoshan Xu Papers
Organic spintronic devices have been appealing because of the long spin lifetime of the charge carriers in the organic materials and their low cost, flexibility and chemical diversity. In previous studies, the control of resistance of organic spin valves is generally achieved by the alignment of the magnetization directions of the two ferromagnetic electrodes, generating magnetoresistance. Here we employ a new knob to tune the resistance of organic spin valves by adding a thin ferroelectric interfacial layer between the ferromagnetic electrode and the organic spacer: the magnetoresistance of the spin valve depends strongly on the history of the bias voltage, …
Dynamic Analysis Of Dna Nanoparticle Immobilization To Model Biomaterial Substrates Using Combinatorial Spectroscopic Ellipsometry And Quartz Crystal Microbalance With Dissipation,
2014
University of Nebraska-Lincoln
Dynamic Analysis Of Dna Nanoparticle Immobilization To Model Biomaterial Substrates Using Combinatorial Spectroscopic Ellipsometry And Quartz Crystal Microbalance With Dissipation, Tadas Kasputis, Alex Pieper, Mathias Schubert, Angela K. Pannier
Department of Agricultural and Biological Systems Engineering: Faculty Publications
Gene expression within cells can be altered through gene delivery approaches, which have tremendous potential for gene therapy, tissue engineering, and diagnostics. Substrate-mediated gene delivery describes the delivery of plasmid DNA or DNA complexed with nonviral vectors to cells from a surface, with the DNA immobilized to a substrate through specific or nonspecific interactions. In this work, DNA-nanoparticle (DNA–NP) adsorption to substrates is evaluated using combinatorial, in situ spectroscopic ellipsometry and quartz crystal microbalance with dissipation (SE/QCM-D), to evaluate the basic dynamic processes involved in the adsorption and immobilization of DNA–NP complexes to substrates. The concentration of DNA–NP solutions influences …
Ferroelectricity At The Nanoscale,
2014
Institute of Crystallography, Russian Academy of Sciences, Moscow
Ferroelectricity At The Nanoscale, Vladimir M. Fridkin, Stephen Ducharme
Stephen Ducharme Publications
The properties of ferroelectrics at the nanoscale are reviewed. The term nanoscale is here related to the ferroelectric film thickness (which is by an order of magnitude the size of the critical domain nucleus). The three aspects considered are ferroelectric switching, the scaling of the coercive field, and the bulk photovoltaic effect. While ferroelectricity at the nanoscale has a twenty-year history of study, it is only in the last few years that perovskite ferroelectric films have become a focus of interest.
Coplanar Switching Of Polarization In Thin Films Of Vinylidene Fluoride
Oligomers,
2014
University of Nebraska - Lincoln
Coplanar Switching Of Polarization In Thin Films Of Vinylidene Fluoride Oligomers, Pankaj Sharma, Alexandra Fursina, Shashi Poddar, Stephen Ducharme, Alexei Gruverman
Stephen Ducharme Publications
Switching characteristics of vinylidene fluoride oligomer thin films with molecular chains aligned normal to the substrate and exhibiting a preferential in-plane polarization have been investigated using coplanar geometry of inter-digital electrodes via high-resolution piezoresponse force microscopy. It has been shown that in-plane switching proceeds via non-180 rotation of dipoles mediated by non-stochastic nucleation, expansion, and coalescence of domains. Asgrown multidomain configuration is found to be strongly pinned aided by charged domain walls, and the electrically induced (in-plane) mono-domain states relax to the as-grown state. The observed coercive field (approximately 0.6 MV/m) is two to three orders of magnitude smaller than …
The Spin State Of A Molecular Adsorbate Driven By
The Ferroelectric Substrate Polarization†,
2014
University of Nebraska-Lincoln
The Spin State Of A Molecular Adsorbate Driven By The Ferroelectric Substrate Polarization†, Xin Zhang, Tatiana Palamarciuc, Jean-François Létard, Patrick Rosa, Eduardo Vega Lozada, Fernand Torres, Luis G. Rosa, Bernard Doudin, Peter A. Dowben
Peter Dowben Publications
The spin state of [Fe(H2B(pz)2)2(bipy)] thin films is mediated by changes in the electric field at the interface of organic ferroelectric polyvinylidene fluoride with trifluoroethylene (PVDF–TrFE). Signatures of the molecular crossover transition are evident in changes in the unoccupied states and the related shift from diamagnetic to paramagnetic characteristics. This may point the way to the molecular magneto-electric effect on devices.
Organic Ferroelectric Evaporator With Substrate Cooling
And In Situ Transport Capabilities,
2014
University of Nebraska-Lincoln
Organic Ferroelectric Evaporator With Substrate Cooling And In Situ Transport Capabilities, Keith Foreman, C. Labedz, M. Shearer, Shireen Adenwalla
Shireen Adenwalla Papers
We report on the design, operation, and performance of a thermal evaporation chamber capable of evaporating organic thin films. Organic thin films are employed in a diverse range of devices and can provide insight into fundamental physical phenomena. However, growing organic thin films is often challenging and requires very specific deposition parameters. The chamber presented here is capable of cooling sample substrates to temperatures below 130 K and allows for the detachment of the sample from the cooling stage and in situ transport. This permits the use of multiple deposition techniques in separate, but connected, deposition chambers without breaking vacuum …
