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Condensed Matter Physics Commons

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3,176 full-text articles. Page 105 of 106.

Dynamical Theory Calculations Of Spin-Echo Resolved Grazing-Incidence Scattering From A Diffraction Grating, Rana Ashkar, P. Stonaha, A. L. Washington, V. R. Shah, M. R. Fitzsimmons, B. Maranville, C. F. Majkrzak, W. T. Lee, W. L. Schaich, Roger Pynn 2010 Indiana University - Bloomington

Dynamical Theory Calculations Of Spin-Echo Resolved Grazing-Incidence Scattering From A Diffraction Grating, Rana Ashkar, P. Stonaha, A. L. Washington, V. R. Shah, M. R. Fitzsimmons, B. Maranville, C. F. Majkrzak, W. T. Lee, W. L. Schaich, Roger Pynn

Faculty Publications from Nebraska Center for Materials and Nanoscience

Neutrons scattered or reflected from a diffraction grating are subject to a periodic potential analogous to the potential experienced by electrons within a crystal. Hence, the wavefunction of the neutrons can be expanded in terms of Bloch waves and a dynamical theory can be applied to interpret the scattering phenomenon. In this paper, a dynamical theory is used to calculate the results of neutron spin-echo resolved grazing-incidence scattering (SERGIS) from a silicon diffraction grating with a rectangular profile. The calculations are compared with SERGIS measurements made on the same grating at two neutron sources: a pulsed source and a continuous ...


Electrically Driven Magnetism On A Pd Thin Film, Y. Sun, John D. Burton, Evgeny Y. Tsymbal 2010 University of Nebraska - Lincoln

Electrically Driven Magnetism On A Pd Thin Film, Y. Sun, John D. Burton, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

Using first-principles density-functional calculations, we demonstrate that ferromagnetism can be induced and modulated on an otherwise paramagnetic Pd metal thin-film surface through application of an external electric field. As free charges are either accumulated or depleted at the Pd surface to screen the applied electric field, there is a corresponding change in the surface density of states. This change can be made sufficient for the Fermi-level density of states to satisfy the Stoner criterion, driving a transition locally at the surface from a paramagnetic state to an itinerant ferromagnetic state above a critical applied electric field, Ec. Furthermore, due ...


Effect Of Spin-Dependent Screening On Tunneling Electroresistance And Tunneling Magnetoresistance In Multiferroic Tunnel Junctions, M. Ye. Zhuravlev, S. Maekawa, Evgeny Y. Tsymbal 2010 University of Nebraska - Lincoln

Effect Of Spin-Dependent Screening On Tunneling Electroresistance And Tunneling Magnetoresistance In Multiferroic Tunnel Junctions, M. Ye. Zhuravlev, S. Maekawa, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

Using a ferroelectric barrier as a functional material in a (magnetic) tunnel junction has recently attracted significant interest due to new functionalities not available in conventional tunnel junctions. Switching a ferroelectric polarization of the barrier alters conductance resulting in a tunneling electroresistance (TER) effect. Using a ferroelectric barrier in a magnetic tunnel junction makes it mutiferroic where TER coexists with tunneling magnetoresistance (TMR). Here we develop a simple model for a multiferroic tunnel junction (MFTJ) which consists of two ferromagnetic electrodes separated by a ferroelectric barrier layer. The model explicitly includes the spin-dependent screening potential and thus extends previously developed ...


Ferroelectric Dead Layer Driven By A Polar Interface, Y. Wang, Manish K. Niranjan, K. Janicka, Julian P. Velev, Mikhail Ye Zhuravlev, Sitaram Jaswal, Evgeny Y. Tsymbal 2010 University of Nebraska - Lincoln

Ferroelectric Dead Layer Driven By A Polar Interface, Y. Wang, Manish K. Niranjan, K. Janicka, Julian P. Velev, Mikhail Ye Zhuravlev, Sitaram Jaswal, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

Based on first-principles and model calculations we investigate the effect of polar interfaces on the ferroelectric stability of thin-film ferroelectrics. As a representative model, we consider a TiO2 -terminated BaTiO3 film with LaO monolayers at the two interfaces that serve as doping layers. We find that the polar interfaces create an intrinsic electric field that is screened by the electron charge leaking into the BaTiO3 layer. The amount of the leaking charge is controlled by the boundary conditions which are different for three heterostructures considered, namely, vacuum/LaO/BaTiO3 /LaO, LaO/BaTiO3 , and SrRuO3 ...


Evolution Of The Band Alignment At Polar Oxide Interfaces, John D. Burton, Evgeny Y. Tsymbal 2010 University of Nebraska-Lincoln

Evolution Of The Band Alignment At Polar Oxide Interfaces, John D. Burton, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

First-principles calculations demonstrate the evolution of the band alignment at La0.7A0.3MnO3 / La1−xAxO / TiO2 / SrTiO3 (001) heterointerfaces, where A=Ca, Sr, or Ba, as the interfacial A-site composition, La1−xAx, is varied from x=0.5 to x=1.0. This variation leads to a linear change in the SrTiO3 valence-band offset with respect to the Fermi level of the La0.7A0.3MnO3 metal electrode and hence to a linear change in the Schottky barrier height at this ...


Comparison Of Flight And Ground Tests Of Environmental Degradation Of Misse-6 Suspecs Materials, JR Dennison, John Prebola, Amberly Evans, Danielle Fullmer, Joshua L. Hodges, Dustin H. Crider, Daniel S. Crews 2010 Utah State Univesity

Comparison Of Flight And Ground Tests Of Environmental Degradation Of Misse-6 Suspecs Materials, Jr Dennison, John Prebola, Amberly Evans, Danielle Fullmer, Joshua L. Hodges, Dustin H. Crider, Daniel S. Crews

Conference Proceedings

The effects of prolonged exposure to the LEO space environment and charge-enhanced contamination on optical, thermal, and electron emission and transport properties of common spacecraft materials have been investigated by comparing pre- and post-flight characterization measurements. The State of Utah Space Environment and Contamination Study (SUSpECS) deployed in March 2008 on board the Materials International Space Station Experiment (MISSE-6) payload, was exposed for ~18 months on the exterior of the International Space Station (ISS), and was retrieved in September 2009. A total of 165 samples were mounted on three separate SUSpECS panels on the ram and wake sides on the ...


Efficiency Of Parallel Tempering For Ising Systems, Stephan Burkhardt 2010 University of Massachusetts Amherst

Efficiency Of Parallel Tempering For Ising Systems, Stephan Burkhardt

Masters Theses 1911 - February 2014

The efficiency of parallel tempering Monte Carlo is studied for a two-dimensional Ising system of length L with N=L^2 spins. An external field is used to introduce a difference in free energy between the two low temperature states.

It is found that the number of replicas R_opt that optimizes the parallel tempering algorithm scales as the square root of the system size N. For two symmetric low temperature states, the time needed for equilibration is observed to grow as L^2.18. If a significant difference in free energy is present between the two states, this changes to ...


Zero Field Magnetic Phase Transitions And Anomalous Low Temperature Upturn In Resistivity Of Single Crystalline Α-Tmalb4, N. H. Sung, Andreas Kreyssig, H. Kim, Makariy A. Tanatar, J. S. Rhyee, B. Y. Kang, M. G. Kim, J. Y. Kim, Paul C. Canfield, Ruslan Prozorov, Alan I. Goldman, B. K. Cho 2010 Gwangju Institute of Science and Technology

Zero Field Magnetic Phase Transitions And Anomalous Low Temperature Upturn In Resistivity Of Single Crystalline Α-Tmalb4, N. H. Sung, Andreas Kreyssig, H. Kim, Makariy A. Tanatar, J. S. Rhyee, B. Y. Kang, M. G. Kim, J. Y. Kim, Paul C. Canfield, Ruslan Prozorov, Alan I. Goldman, B. K. Cho

Ames Laboratory Publications

In this study, pure α-TmAlB4 (YCrB4structure)single crystals were grown with no β-TmAlB4 (ThMoB4structure) intergrowth, and zero magnetic fieldtransitions were confirmed through specific heat capacity, magnetization, and electric resistivity measurements. The anomalous magnetic transition was found at approximately 6.2 K with long range antiferromagnetictransition at 5.6 K. The difference in field dependence between these two transitions indicates that they do not share a common magnetic origin. In addition, we investigated electrical resistivity down to 20 mK, and found upturn behavior at around 0.8 K. The low temperature upturn anomaly in resistivity was not found for other compounds ...


Electro-Optic And Magneto-Dielectric Properties Of Multifunctional Nitride And Oxide Materials, Ambesh Dixit 2010 Wayne State University

Electro-Optic And Magneto-Dielectric Properties Of Multifunctional Nitride And Oxide Materials, Ambesh Dixit

Wayne State University Dissertations

ABSTRACT

Materials that simultaneously exhibit different physical properties provide a rich area of research leading to the development of new devices. For example, materials having a strong coupling between charge and spin degrees of freedom are essential to realizing a new class of devices referred to generally as spintronics. However, these multifunctional systems pose new scientific challenges in understanding the origin and mechanisms for cross-control of different functionalities. The core of this Ph.D. dissertation deals with multifunctional nitride and oxide compound semiconductors as well as multiferroic magnetic oxide systems by investigating structural, optical, electrical, magnetic, magnetodielectric and magnetoelectric properties ...


Harmonic Sputtering Theory, Zhu Lin Zhang 2010 Wayne State University

Harmonic Sputtering Theory, Zhu Lin Zhang

Wayne State University Dissertations

ABSTRACT

HARMONIC SPUTTERING THEORY

By

ZHU LIN ZHANG

February 2010

Advisor: Dr. Karur R. Padmanabhan

Major: Physics

Degree: Doctor of Philosophy

Based on the standard Botzmann equation in Classical Statistics Mechanics, we have derived a variety of Linear Transport Equations appeared in Sputtering Theory for a random, infinite multi-components medium. The pertinent relations among these Linear Transport Equations have been studied in detail. We have introduced exact classical scattering cross-sections of power potential interaction collision into these Transport Equations and solved them asymptotically by using Laplace Transformation for both isotropic term and anisotropic term. A pool of analytical asymptotic solutions ...


A Study Of Structure-Property Correlation In V2o5 And Tio2 Based Thin Films As Functional Materials, Chandra Thapa 2010 Wayne State University

A Study Of Structure-Property Correlation In V2o5 And Tio2 Based Thin Films As Functional Materials, Chandra Thapa

Wayne State University Dissertations

ABSTRACT

A STUDY OF STRUCTURE-PROPERTY CORRELATION IN V2O5 AND TiO2 BASED THIN FILMS AS FUNCTIONAL MATERIALS

by

CHANDRA THAPA

June 2010

Advisor: Dr. Ratna Naik

Co-Advisor: Dr. K. R. Padmanabhan

Major: Physics (Condensed Matter)

Degree: Doctor of Philosophy

The focus of this thesis is to study the structure-property correlation in thin films of V2O5 and TiO2 based transition metal oxides as functional materials. V2O5 is investigated as a cathode material for lithium ion battery and TiO2 as a high-K dielectric material.

We studied V2O5 thin films prepared by spin coating using three different types of precursors, MOD precursor, sol-gel organic ...


Measuring The Nanomechanics Of Nanoconfined Water Layers, Shah Haidar Khan 2010 Wayne State University

Measuring The Nanomechanics Of Nanoconfined Water Layers, Shah Haidar Khan

Wayne State University Dissertations

Nanoconfined water has been the subject of special interest due to its applications in various fields such as biology, geology, medicine, and engineering tribology. While there is a general agreement on the layering of water molecules along atomically smooth surfaces, the behavior and properties of nanoconfined water is still poorly understood. A significant controversy exists whether there is a phase transformation imposed by confinement. We have measured the stiffness and damping coefficient of nanoconfined water using a small amplitude (0.5-1 Å) atomic force microscope. The results were analyzed with the help of two viscoelastic models, the Kelvin model and ...


Lattice Dynamical Probe Of Charge Order And Antipolar Bilayer Stacking In Lufe2o4, X. S. Xu, J. de Groot, Q.-C. Sun, B. C. Sales, D. Mandrus, M. Angst, A. P. Litvinchuk, J. L. Musfeldt 2010 University of Nebraska-Lincoln

Lattice Dynamical Probe Of Charge Order And Antipolar Bilayer Stacking In Lufe2o4, X. S. Xu, J. De Groot, Q.-C. Sun, B. C. Sales, D. Mandrus, M. Angst, A. P. Litvinchuk, J. L. Musfeldt

Xiaoshan Xu Papers

We investigated the infrared response of LuFe2O4 through the series of charge, magnetic, and structural transitions. All vibrational modes couple strongly to the charge order, whereas the LuO zone-folding modes are also sensitive to magnetic order and structural distortion. The dramatic splitting of the LuO2 layer mode is attributed to charge-rich/poor proximity effects and its temperature dependence reveals the antipolar nature of the W layer pattern.


Tunable Band Gap In Bi(Fe1−Xmnx)O3 Films, X. S. Xu, J. F. Ihlefeld, J. H. Lee, O. K. Ezekoye, E. Vlahos, R. Ramesh, V. Gopalan, X. Q. Pan, D. G. Schlom, J. L. Musfeldt 2010 University of Nebraska-Lincoln

Tunable Band Gap In Bi(Fe1−Xmnx)O3 Films, X. S. Xu, J. F. Ihlefeld, J. H. Lee, O. K. Ezekoye, E. Vlahos, R. Ramesh, V. Gopalan, X. Q. Pan, D. G. Schlom, J. L. Musfeldt

Xiaoshan Xu Papers

In order to investigate band gap tunability in polar oxides, we measured the optical properties of a series of Bi(Fe1−xMnx)O3 thin films. The absorption response of the mixed metal solid solutions is approximately a linear combination of the characteristics of the two end members, a result that demonstrates straightforward band gap tunability in this system.


Magnetodielectric Coupling Of Infrared Phonons In Single-Crystal Cu2oseo3, K. H. Miller, X. S. Xu, H. Berger, E. S. Knowles, D. J. Arenas, M. W. Meisel, D. B. Tanner 2010 University of Florida

Magnetodielectric Coupling Of Infrared Phonons In Single-Crystal Cu2oseo3, K. H. Miller, X. S. Xu, H. Berger, E. S. Knowles, D. J. Arenas, M. W. Meisel, D. B. Tanner

Xiaoshan Xu Papers

Reflection and transmission as a function of temperature (5–300 K) have been measured on a single crystal of the magnetoelectric ferrimagnetic compound Cu2OSeO3 utilizing light spanning the far infrared to the visible portions of the electromagnetic spectrum. The complex dielectric function and optical properties were obtained via Kramers-Kronig analysis and by fits to a Drude-Lortentz model. The fits of the infrared phonons show a magnetodielectric effect near the transition temperature (Tc~60 K). Assignments to strong far-infrared phonon modes have been made, especially those exhibiting anomalous behavior around the transition temperature.


Adsorption-Controlled Growth Of Bimno3 Films By Molecular-Beam Epitaxy, J. H. Lee, X. Ke, R. Misra, J. F. Ihlefeld, X. S. Xu, Z. G. Mei, T. Heeg, M. Roeckerath, J. Schubert, Z. K. Liu, J. L. Musfeldt, P. Schiffer, D. G. Schlom 2010 Cornell University

Adsorption-Controlled Growth Of Bimno3 Films By Molecular-Beam Epitaxy, J. H. Lee, X. Ke, R. Misra, J. F. Ihlefeld, X. S. Xu, Z. G. Mei, T. Heeg, M. Roeckerath, J. Schubert, Z. K. Liu, J. L. Musfeldt, P. Schiffer, D. G. Schlom

Xiaoshan Xu Papers

We have developed the means to grow BiMnO3 thin films with unparalleled structural perfection by reactive molecular-beam epitaxy and determined its band gap. Film growth occurs in an adsorption-controlled growth regime. Within this growth window bounded by oxygen pressure and substrate temperature at a fixed bismuth overpressure, single-phase films of the metastable perovskite BiMnO3 may be grown by epitaxial stabilization. X-ray diffraction reveals phase-pure and epitaxial films with w rocking curve full width at half maximum values as narrow as 11 arc sec (0.003°). Optical absorption measurements reveal that BiMnO3 has a direct band gap of ...


Reflectivity Of A Cholesteric Liquid Crystal, Justin Lawson 2010 California Polytechnic State University - San Luis Obispo

Reflectivity Of A Cholesteric Liquid Crystal, Justin Lawson

Physics

In this paper we investigate the light properties of a chiral liquid crystal or a crystal for which the director angle relative to some fixed axis changes as a function of the crystal depth. Sometimes a dopant can introduce a chirality or "twist" in a nematic liquid crystal. For such cases of non-linear depth dependence (where chirality is determined by a diffusion equation) we may use this research to work backwards from a crystal's light properties to intensity and duration of dopant exposure.


Two-Way Diffusion Model For Short Exposure Holographic Grating Formation In Acrylamide-Based Photopolymer, Tzvetanka Babeva, Izabela Naydenova, Dana Mackey, Suzanne Martin, Vincent Toal 2010 Bulgarian Academy of Sciences

Two-Way Diffusion Model For Short Exposure Holographic Grating Formation In Acrylamide-Based Photopolymer, Tzvetanka Babeva, Izabela Naydenova, Dana Mackey, Suzanne Martin, Vincent Toal

Articles

A theoretical model for formation of a short exposure holographic grating is presented. The model accounts for both monomer and polymer diffusion and distinguishes between short polymer chains capable of diffusing and long polymer chains that are immobile. It is shown that the experimentally observed decrease of diffraction efficiency at higher spatial frequency can be predicted by assuming diffusion of short-chain polymers away from the bright fringes. The time evolution of the refractive index modulation after short exposure is calculated and compared with experimental results. The effects of diffusion coefficients, polymerization rates, intensity and spatial frequency of recording on the ...


Optimisation Of An Acrylamide-Based Photopolymer System For Holographic Inscription Of Surface Patterns With Sub-Micron Resolution, Kevin Trainer, Kevin Wearen, Dimana Nazarova, Izabela Naydenova, Vincent Toal 2010 Drexel University

Optimisation Of An Acrylamide-Based Photopolymer System For Holographic Inscription Of Surface Patterns With Sub-Micron Resolution, Kevin Trainer, Kevin Wearen, Dimana Nazarova, Izabela Naydenova, Vincent Toal

Articles

We describe the optimisation of the holographic patterning of sub-micrometer surface relief structures in an acrylamide-based photopolymer. A substantial improvement in the photoinduced surface relief resolution was achieved by altering the photopolymer chemical composition and by introducing a single step post recording thermal treatment of the layers. It was observed that, by optimisation of the chemical composition of the photopolymer layers, the maximum achievable spatial frequency increases from 200 l/mm to 550 l/mm. The improvement of the surface relief amplitude by alteration of the chemical composition is limited due to the fact that both decrease of the plasticiser ...


A Diffusion Model For Spatially Dependent Photopolymerization, Dana Mackey, Tzvetanka Babeva, Izabela Naydenova, VIncent Toal 2010 Technological University Dublin

A Diffusion Model For Spatially Dependent Photopolymerization, Dana Mackey, Tzvetanka Babeva, Izabela Naydenova, Vincent Toal

Articles

Photopolymers represent an attractive class of optical recording materials due to properties such as high refractive index modulation, dry film processing, long shelf life, etc. Applications include holographically based devices for optical storage disks, optical interconnections, optical memories and filters. This paper will address the dynamics of short-exposure holographic grating formation; a new mathematical model is proposed with the aim of understanding the experimental observations of low diffraction efficiency in high spatial frequency gratings.


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