Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

2012

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 8071 - 8100 of 8516

Full-Text Articles in Physical Sciences and Mathematics

Quantum Tunneling Of The Magnetic Moment In A Free Nanoparticle, Michael F. O'Keeffe, Eugene M. Chudnovsky, Dmitry A. Garanin Jan 2012

Quantum Tunneling Of The Magnetic Moment In A Free Nanoparticle, Michael F. O'Keeffe, Eugene M. Chudnovsky, Dmitry A. Garanin

Publications and Research

We study tunneling of the magnetic moment in a particle that has full rotational freedom. Exact energy levels are obtained and the ground-state magnetic moment is computed for a symmetric rotor. The effect of the mechanical freedom on spin tunneling manifests itself in a strong dependence of the magnetic moment on the moments of inertia of the rotor. Energy of the particle exhibits quantum phase transitions between states with different values of the magnetic moment. Particles of various shapes are investigated and quantum phase diagram is obtained.

Go to article

Age Composition And Distribution Of Red Drum (Sciaenops Ocellatus) In Offshore Waters Of The North Central Gulf Of Mexico: An Evaluation Of A Stock Under A Federal Harvest Moratorium, Sean P. Powers, Crystal Hightower, J. Marcus Drymon, Matthew W. Johnson Jan 2012

Age Composition And Distribution Of Red Drum (Sciaenops Ocellatus) In Offshore Waters Of The North Central Gulf Of Mexico: An Evaluation Of A Stock Under A Federal Harvest Moratorium, Sean P. Powers, Crystal Hightower, J. Marcus Drymon, Matthew W. Johnson

University Faculty and Staff Publications

Because of a lack of fishery- dependent data, assessment of the recovery of fish stocks that undergo the most aggressive form of management, namely harvest moratoriums, remains a challenge. Large schools of red drum (Sclaenops ocellatus) were common along the northern Gulf of Mexico until the late 1980s when increased fishing effort quickly depleted the stock. After 24 years of harvest moratorium on red drum in federal waters, the stock is in need of reassessment; however, fishery dependent data are not available in federal waters and fishery-independent data are limited. We document the distribution, age composition, growth, and condition of …

Go to article

Outer Restricted Derivations Of Nilpotent Restricted Lie Algebras, Jorg Feldvoss, Salvatore Siciliano, Thomas Weigel Jan 2012

Outer Restricted Derivations Of Nilpotent Restricted Lie Algebras, Jorg Feldvoss, Salvatore Siciliano, Thomas Weigel

University Faculty and Staff Publications

In this paper we prove that every finite-dimensional nilpotent restricted Lie algebra over a field of prime characteristic has an outer restricted derivation whose square is zero unless the restricted Lie algebra is a torus or it is one-dimensional or it is isomorphic to the three-dimensional Heisenberg algebra in characteristic two as an ordinary Lie algebra. This result is the restricted analogue of a result of Tôgô on the existence of nilpotent outer derivations of ordinary nilpotent Lie algebras in arbitrary characteristic and the Lie-theoretic analogue of a classical group-theoretic result of Gaschütz on the existence of p-power automorphisms …

Go to article

Quantum Deflagration And Supersonic Fronts Of Tunneling In Molecular Magnets, Dmitry A. Garanin, Saaber Shoyed Jan 2012

Quantum Deflagration And Supersonic Fronts Of Tunneling In Molecular Magnets, Dmitry A. Garanin, Saaber Shoyed

Publications and Research

Theory of magnetic deflagration taking into account dipolar-controlled spin tunneling has been applied to the realistic model of molecular magnet Mn_12 Ac. At small transverse field, the front speed v has tunneling maxima on the bias field B_z reflecting those of the molecular spin's relaxation rate calculated from the density-matrix equation. At high transverse field, spin tunneling directly out of the metastable ground state leads to front speeds that can exceed the speed of sound. Both for the weak and strong transverse field, the spatial profile of the deflagration front near tunneling resonances shows a front of tunneling that triggers …

Go to article

Dipolar-Controlled Spin Tunneling And Relaxation In Molecular Magnets, Dmitry A. Garanin Jan 2012

Dipolar-Controlled Spin Tunneling And Relaxation In Molecular Magnets, Dmitry A. Garanin

Publications and Research

Spin tunneling in molecular magnets controlled by dipole-dipole interactions (DDI) in the disordered state has been considered numerically on the basis of the microscopic model using the quantum mean-field approximation. In the actual case of a strong DDI spin coherence is completely lost and there is a slow relaxation of magnetization, described by t^{3/4} at short times. Fast precessing nuclear spins, included in the model microscopically, only moderately speed up the relaxation.

Go to article

Cosmic String Interactions Induced By Gauge And Scalar Fields, Daniel N. Kabat, Debajyoti Sarkar Jan 2012

Cosmic String Interactions Induced By Gauge And Scalar Fields, Daniel N. Kabat, Debajyoti Sarkar

Publications and Research

We study the interaction between two parallel cosmic strings induced by gauge fields and by scalar fields with non-minimal couplings to curvature. For small deficit angles the gauge field behaves like a collection of non-minimal scalars with a specific value for the non-minimal coupling. We check this equivalence by computing the interaction energy between strings at first order in the deficit angles. This result provides another physical context for the "contact terms" which play an important role in the renormalization of black hole entropy due to a spin-1 field.

Go to article

Holographic Representation Of Bulk Fields With Spin In Ads/Cft, Daniel N. Kabat, Gilad Lifschytz, Shubho Roy, Debajyoti Sarkar Jan 2012

Holographic Representation Of Bulk Fields With Spin In Ads/Cft, Daniel N. Kabat, Gilad Lifschytz, Shubho Roy, Debajyoti Sarkar

Publications and Research

We develop the representation of bulk fields with spin one and spin two in anti-de Sitter space, as non-local observables in the dual CFT. Working in holographic gauge in the bulk, at leading order in 1/N bulk gauge fields are obtained by smearing boundary currents over a sphere on the complexified boundary, while linearized metric fluctuations are obtained by smearing the boundary stress tensor over a ball. This representation respects AdS covariance up to a compensating gauge transformation. We also consider massive vector fields, where the bulk field is obtained by smearing a non-conserved current. We compute bulk two-point functions …

Go to article

Casimir Effect: Edges And Diffraction, Dimitra Karabali Jan 2012

Casimir Effect: Edges And Diffraction, Dimitra Karabali

Publications and Research

The Casimir effect refers to the existence of a macroscopic force between conducting plates in vacuum due to quantum fluctuations of fields. These forces play an important role, among other things, in the design of nano-scale mechanical devices. Accurate experimental observations of this phenomenon have motivated the development of new theoretical approaches in dealing with the effects of different geometries, temperature etc. In this talk, I will focus on a new method we have developed in calculating the contribution to the Casimir effect due to diffraction from edges and holes in different geometries, at zero and at finite temperature.

Go to article

Ccpa Regulates Arginine Biosynthesis In Staphylococcus Aureus Through Repression Of Proline Catabolism, Austin S. Nuxoll, Steven M. Halouska, Marat R. Sadykov, Mark L. Hanke, Kenneth W. Bayles, Tammy Kielian, Robert Powers, Paul D. Fey Jan 2012

Ccpa Regulates Arginine Biosynthesis In Staphylococcus Aureus Through Repression Of Proline Catabolism, Austin S. Nuxoll, Steven M. Halouska, Marat R. Sadykov, Mark L. Hanke, Kenneth W. Bayles, Tammy Kielian, Robert Powers, Paul D. Fey

Department of Chemistry: Faculty Publications

Staphylococcus aureus is a leading cause of community-associated and nosocomial infections. Imperative to the success of S. aureus is the ability to adapt and utilize nutrients that are readily available. Genomic sequencing suggests that S. aureus has the genes required for synthesis of all twenty amino acids. However, in vitro experimentation demonstrates that staphylococci have multiple amino acid auxotrophies, including arginine. Although S. aureus possesses the highly conserved anabolic pathway that synthesizes arginine via glutamate, we demonstrate here that inactivation of ccpA facilitates the synthesis of arginine via the urea cycle utilizing proline as a substrate. Mutations within putA, rocD, …

Go to article

Growth Diagram And Magnetic Properties Of Hexagonal Lufe2o4 Thin Films, Wenbin Wang, Zheng Gai, Miaofang Chi, Jason D. Fowlkes, Jieyu Yi, Leyi Zhu, Xuemei Cheng, David J. Keavney, Paul C. Snijders, Thomas Z. Ward, Jian Shen, Xiaoshan Xu Jan 2012

Growth Diagram And Magnetic Properties Of Hexagonal Lufe2o4 Thin Films, Wenbin Wang, Zheng Gai, Miaofang Chi, Jason D. Fowlkes, Jieyu Yi, Leyi Zhu, Xuemei Cheng, David J. Keavney, Paul C. Snijders, Thomas Z. Ward, Jian Shen, Xiaoshan Xu

Xiaoshan Xu Papers

Agrowth diagram of Lu-Fe-O compounds on MgO (111) substrates using pulsed laser deposition is constructed based on extensive growth experiments. The LuFe2O4 phase can only be grown in a small range of temperature and O2 pressure conditions. An understanding of the growth mechanism of Lu-Fe-O compound films is offered in terms of the thermochemistry at the surface. Superparamagnetism is observed in the LuFe2O4 film and is explained in terms of the effect of the impurity hexagonal LuFeO3 (h-LuFeO3) phase and structural defects.

Go to article

Crystal Field Splitting And Optical Bandgap Of Hexagonal Lufeo3 Films, Wenbin Wang, Hongwei Wang, Xiaoying Xu, Leyi Zhu, Lixin He, Elizabeth Wills, Xuemei Cheng, David J. Keavney, Jian Shen, Xifan Wu, Xiaoshan Xu Jan 2012

Crystal Field Splitting And Optical Bandgap Of Hexagonal Lufeo3 Films, Wenbin Wang, Hongwei Wang, Xiaoying Xu, Leyi Zhu, Lixin He, Elizabeth Wills, Xuemei Cheng, David J. Keavney, Jian Shen, Xifan Wu, Xiaoshan Xu

Xiaoshan Xu Papers

Hexagonal LuFeO3 films have been studied using x-ray absorption and optical spectroscopy. The crystal splitting of Fe3+ is extracted as Ee' - Ee" = 0.7 eV and Ea'1 - Ee' = 0.9 eV, and a 2.0 eV optical bandgap is determined assuming a direct gap. First-principles calculations confirm the experiments that the relative energies of crystal field splitting states do follow Ea'1 > Ee' > Ee" with slightly underestimated values and a bandgap of 1.35 eV.

Go to article

Isothermal Entropy Changes In Nanocomposite Co:Ni67Cu33, Steven A. Michalski, Ralph Skomski, Xingzhong Li, Damien Le Roy, Tathagata Mukherjee, Christian Binek, David J. Sellmyer Jan 2012

Isothermal Entropy Changes In Nanocomposite Co:Ni67Cu33, Steven A. Michalski, Ralph Skomski, Xingzhong Li, Damien Le Roy, Tathagata Mukherjee, Christian Binek, David J. Sellmyer

David Sellmyer Publications

The temperature-dependent magnetic properties of artificial rare-earth, free-magnetic nanostructures are investigated for magnetic cooling. We consider two-phase nanocomposites, where 2 nm nanoclusters of cobalt are embedded in a Ni67Cu33 matrix. Several composite films were produced by cluster deposition. The average Co nanocluster size can be tuned by varying the deposition conditions. Isothermalmagnetization curves weremeasured at various temperatures 150K

Go to article

Magnetism Of Directly Ordered Sm-Co Clusters, Balamurugan Balasubramanian, Ralph Skomski, Xingzhong Li, George C. Hadjipanayis, David J. Sellmyer Jan 2012

Magnetism Of Directly Ordered Sm-Co Clusters, Balamurugan Balasubramanian, Ralph Skomski, Xingzhong Li, George C. Hadjipanayis, David J. Sellmyer

David Sellmyer Publications

Sm-Co bulk alloys have shown superior permanent-magnet properties, but research on Sm-Co nanoparticles is challenging because of the need to control particle size, size-distribution, crystalline ordering, and phase purity. In the present study, a cluster-deposition method was used to produce Sm-Co nanoparticles having desired crystal structures without the requirement of subsequent high-temperature thermal annealing. Poorly crystallized SmCo5 nanoparticles exhibit a low room-temperature coercivity of only 100 Oe, whereas crystalline SmCo5 and Sm2Co17 nanoparticles show room-temperature coercivities of 2000 and 750 Oe, respectively. The direct synthesis of Sm-Co nanoparticles having sizes of less than 10 nm …

Go to article

One-Step Fabrication Of L10 Fept Nanocubes And Rods By Cluster Beam Deposition, W Li, O Akdogan, George C. Hadjipanayis, Ralph Skomski, David J. Sellmyer Jan 2012

One-Step Fabrication Of L10 Fept Nanocubes And Rods By Cluster Beam Deposition, W Li, O Akdogan, George C. Hadjipanayis, Ralph Skomski, David J. Sellmyer

David Sellmyer Publications

In this work, single crystal L10 FePt nanocubes have been successfully produced by a cluster beam deposition technique without the need of post annealing. Particles have been deposited by dc magnetron sputtering using high Ar pressures on both single crystal Si substrates and Au grids for the measurement of magnetic and structural properties, respectively. The nanocubes have a uniform size distribution with an average size of 5nm. At 1 Torr, the particles have the L10 structure with an order parameter of 0.5 and a RT coercivity of 2 kOe with high switching fields observed in the hysteresis loop. …

Go to article

Magnetism Of Dilute Co(Hf) And Co(Pt) Nanoclusters, Balamurugan Balasubramanian, Ralph Skomski, Xingzhong Li, Shah R. V, Priyanka Manchanda, Arti Kashyap, David J. Sellmyer Jan 2012

Magnetism Of Dilute Co(Hf) And Co(Pt) Nanoclusters, Balamurugan Balasubramanian, Ralph Skomski, Xingzhong Li, Shah R. V, Priyanka Manchanda, Arti Kashyap, David J. Sellmyer

David Sellmyer Publications

An investigation of the magnetic properties of Co-rich nanoparticles alloyed with a small fraction of Pt and Hf is presented. Co(Hf) and Co(Pt) nanoparticles with less than 15 at% of dopants were produced using a cluster-deposition method. The nanoparticles have sizes of less than 10 nm and show improved magnetic properties upon doping. Maximum coercivities of 900 Oe (at 300 K) and 2000 Oe (at 10 K) were observed for Co nanoparticles alloyed with 14.1 at% of Hf. Doped nanoparticles also exhibit high anisotropies, such as K1¼9.98 Mergs=cm3 (14.1 at% of Hf) and K1¼8.24 Mergs=cm …

Go to article

Aligned And Exchange-Coupled L10 (Fe,Co)Pt-Based Magnetic Films, Yi Liu, Thomas A. George, Ralph Skomski, David J. Sellmyer Jan 2012

Aligned And Exchange-Coupled L10 (Fe,Co)Pt-Based Magnetic Films, Yi Liu, Thomas A. George, Ralph Skomski, David J. Sellmyer

David Sellmyer Publications

Films of aligned L10-structure (Fe,Co)Pt with fcc Fe(Co,Pt) are synthesized by co-sputtering Fe, Co, and Pt on an (001) MgO substrate with in situ heating at 830 degrees C. The nanostructures and magnetic properties of the films are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID). The compositions of the samples (Fe,Co)xPt1-x are designed to maintain an atomic Fe: Co ratio of 65: 35 while increasing the Fe,Co content in each successive sample. In samples with low Fe and Co concentration, the XRD patterns exhibit three strong peaks, …

Go to article

A Quantum-Mechanical Relaxation Model, Ralph Skomski, Arti Kashyap, David J. Sellmyer Jan 2012

A Quantum-Mechanical Relaxation Model, Ralph Skomski, Arti Kashyap, David J. Sellmyer

David Sellmyer Publications

The atomic origin of micromagnetic damping is investigated by developing and solving a quantum-mechanical relaxation model. A projection-operator technique is used to derive an analytical expression for the relaxation time as a function of the heat-bath and interaction parameters. The present findings are consistent with earlier research beyond the Landau-Lifshitz-Gilbert (LLG) equation and show that the underlying relaxation mechanism is very general. Zermelo’s recurrence paradox means that there is no true irreversibility in non-interacting nanoparticles, but the corresponding recurrence times are very long and can be ignored in many cases.

Go to article

Structural, Magnetic, And Electron Transport Properties Of Mnbi:Fe Thin Films, Parashu Kharel, Xingzhong Li, Shah R. Valloppilly, Nabil M. Al-Aqtash, K. Tarawneh, Renat F. Sabirianov, Ralph Skomski, David J. Sellmyer Jan 2012

Structural, Magnetic, And Electron Transport Properties Of Mnbi:Fe Thin Films, Parashu Kharel, Xingzhong Li, Shah R. Valloppilly, Nabil M. Al-Aqtash, K. Tarawneh, Renat F. Sabirianov, Ralph Skomski, David J. Sellmyer

David Sellmyer Publications

The structural, magnetic, and electron transport properties of Mn55=xFexBi45 (x¼0, 2, 4, 5, 8, 11, 13, 16) films prepared by multilayer deposition and annealing using e-beam evaporation have been investigated. Fe doping has produced a significant change in the magnetic properties of the samples including the decrease in saturation magnetization and magnetocrystalline anisotropy and increase in coercivity. Although the magnetization shows a smooth decrease with increasing Fe concentration, the coercivity jumps abruptly from 8.5 kOe to 22 kOe as Fe content changes from 4% to 5%, but the change in coercivity is small as the concentration goes beyond 5%. The …

Go to article

Ultrahard Magnetic Nanostructures, P. K. Sahota, Yi Liu, Ralph Skomski, Priyanka Manchanda, R. Zhang, M. Franchin, H. Fangohr, George C. Hadjipanayis, Arti Kashyap, David J. Sellmyer Jan 2012

Ultrahard Magnetic Nanostructures, P. K. Sahota, Yi Liu, Ralph Skomski, Priyanka Manchanda, R. Zhang, M. Franchin, H. Fangohr, George C. Hadjipanayis, Arti Kashyap, David J. Sellmyer

David Sellmyer Publications

The performance of hard-magnetic nanostructures is investigated by analyzing the size and geometry dependence of thin-film hysteresis loops. Compared to bulk magnets, weight and volume are much less important, but we find that the energy product remains the main figure of merit down to very small features sizes. However, hysteresis loops are much easier to control on small length scales, as epitomized by Fe-Co-Pt thin films with magnetizations of up to 1.78 T and coercivities of up to 2.52 T. Our numerical and analytical calculations show that the feature size and geometry have a big effect on the hysteresis loop. …

Go to article

Assembly Of Uniaxially Aligned Rare-Earth-Free Nanomagnets, Balamurugan Balamurugan, Bhaskar Das, Shah R. Valloppilly, Ralph Skomski, Xingzhong Li, David J. Sellmyer Jan 2012

Assembly Of Uniaxially Aligned Rare-Earth-Free Nanomagnets, Balamurugan Balamurugan, Bhaskar Das, Shah R. Valloppilly, Ralph Skomski, Xingzhong Li, David J. Sellmyer

David Sellmyer Publications

We report HfCo7 nanoparticles with appreciable permanent-magnet properties (magnetocrystalline anisotropy K1≈10 Mergs/cm3, coercivity Hc ≈ 4.4 kOe, and magnetic polarization Js≈10.9 kG at 300 K) deposited by a single-step cluster-deposition method. The direct crystalline-ordering of nanoparticles during the gas-aggregation process, without the requirement of a high-temperature thermal annealing, provides an unique opportunity to align their easy axes uniaxially by applying a magnetic field of about 5 kOe prior to deposition, and subsequently to fabricate exchange-coupled nanocomposites having Js as high as 16.6 kG by co-depositing soft magnetic Fe-Co. This study suggests …

Go to article

Observation And Identification Of Metastable Excited States In Ultrafast Laser-Ionized Pyridine, David B. Foote, Timothy D. Scarborough, Cornelis J. Uiterwaal Jan 2012

Observation And Identification Of Metastable Excited States In Ultrafast Laser-Ionized Pyridine, David B. Foote, Timothy D. Scarborough, Cornelis J. Uiterwaal

C.J.G.J. Uiterwaal Publications

We report on the fragmentation of ionized pyridine (C5H5N) molecules by focused 50 fs, 800 nm laser pulses. Such ionization produces several metastable ionic states that fragment within the field-free drift region of a reflectron- type time of flight mass spectrometer, with one particular metastable dissociation being the leading fragmentation process. Because the time of flight is no longer dependent in a simple way on the mass of the ion, the metastable decay is manifested as an unfocused peak on the mass spectrum that appears at a time of flight not corresponding to an integer mass. …

Go to article

Thermal Quench Effects On Ferroelectric Domain Walls, P. Paruch, A. B. Kolton, X. Hong, C. H. Ahn, T. Giamarchi Jan 2012

Thermal Quench Effects On Ferroelectric Domain Walls, P. Paruch, A. B. Kolton, X. Hong, C. H. Ahn, T. Giamarchi

Xia Hong Publications

Using piezoresponse force microscopy on epitaxial ferroelectric thin films, we have measured the evolution of domain wall roughening as a result of heat-quench cycles up to 735 ◦C, with the effective roughness exponent ζ changing from 0.25 to 0.5. We discuss two possible mechanisms for the observed ζ increase: a quench from a thermal one-dimensional configuration and from a locally equilibrated pinned configuration with a crossover from a two- to one-dimensional regime. We find that the postquench spatial structure of the metastable states, qualitatively consistent with the existence of a growing dynamical length scale whose ultraslow evolution is primarily controlled …

Go to article

Electron Attachment To Molecules In A Cluster Environment, Ilya I. Fabrikant, S. Caprasecca, Gordon A. Gallup, J. D. Gorfinkiel Jan 2012

Electron Attachment To Molecules In A Cluster Environment, Ilya I. Fabrikant, S. Caprasecca, Gordon A. Gallup, J. D. Gorfinkiel

Gordon Gallup Publications

Low-energy dissociative electron attachment (DEA) to the CF2Cl2 and CF3Cl molecules in a water cluster environment is investigated theoretically. Calculations are performed for the water trimer and water hexamer. It is shown that the DEA cross section is strongly enhanced when the attaching molecule is embedded in a water cluster, and that this cross section grows as the number of water molecules in the cluster increases. This growth is explained by a trapping effect that is due to multiple scattering by water molecules while the electron is trapped in the cluster environment. The trapping increases …

Go to article

Electric Modulation Of Magnetization At The Batio3/La0.67sr0.33mno3 Interfaces, H. Lu, Thomas A. George, Yong Wang, Ihor Ketsman, John D. Burton, C.-W. Bark, Sangjin Ryu, Dong Jik Kim, J. Wang, Christian Binek, Peter A. Dowben, Andrei Sokolov, C. B. Eom, Evgeny Y. Tsymbal, Alexei Gruverman Jan 2012

Electric Modulation Of Magnetization At The Batio3/La0.67sr0.33mno3 Interfaces, H. Lu, Thomas A. George, Yong Wang, Ihor Ketsman, John D. Burton, C.-W. Bark, Sangjin Ryu, Dong Jik Kim, J. Wang, Christian Binek, Peter A. Dowben, Andrei Sokolov, C. B. Eom, Evgeny Y. Tsymbal, Alexei Gruverman

Alexei Gruverman Publications

We report large (>10%) magnetization modulation by ferroelectric polarization reversal in the ferroelectric-ferromagnetic BaTiO3/La0.67Sr0.33MnO3 (BTO/LSMO) heterostructures. We find that the electrically induced change in magnetization is limited to the BTO/LSMO interface but extends about 3 nm deep into the LSMO layer—far beyond the expected screening length of metallic LSMO. It is suggested that this effect is due to a metal-insulator transition occurring at the BTO/LSMO interface as a result of electrostatic doping.

Go to article

Tunnel Electroresistance In Junctions With Ultrathin Ferroelectric Pb(Zr0.2ti0.8)O3 Barriers, Daniel Pantel, Haidong Lu, Silvana Goetze, Peter Werner, Dong Jik Kim, Alexei Gruverman, Dietrich Hesse, Marin Alexe Jan 2012

Tunnel Electroresistance In Junctions With Ultrathin Ferroelectric Pb(Zr0.2ti0.8)O3 Barriers, Daniel Pantel, Haidong Lu, Silvana Goetze, Peter Werner, Dong Jik Kim, Alexei Gruverman, Dietrich Hesse, Marin Alexe

Alexei Gruverman Publications

In ferroelectric tunnel junctions, the ferroelectric polarization state of the barrier influences the quantum-mechanical tunneling through the junction, resulting in tunnel electroresistance (TER). Here, we investigate tunnel electroresistance in Co/PbZr0.2Ti0.8O3/La0.7Sr0.3MnO3 tunnel junctions. The ferroelectric polarization in tunnel junctions with 1.2-1.6 nm (three to four unit cells) PbZr0.2Ti0.8O3 thickness and an area of 0.04 μm2 can be switched by about 1 V yielding a resistive ON/OFF-ratio of about 300 at 0.4 V. Combined piezoresponse force microscopy and electronic transport investigations of these junctions reveal …

Go to article

Orientation Of Doubly Excited States In N2, John E. Furst, Timothy J. Gay, Joshua Machacek, David Kilkoyne, Kenneth W. Mclaughlin Jan 2012

Orientation Of Doubly Excited States In N2, John E. Furst, Timothy J. Gay, Joshua Machacek, David Kilkoyne, Kenneth W. Mclaughlin

Timothy J. Gay Publications

We have measured the total fluorescent intensity and circular polarization of light emitted in 3p 4Po → 3s4P transitions of excited neutral nitrogen atoms created by the photofragmentation of the N2 molecule with circularly polarized light having energies between 21 and 26 eV. The intensity measurements show the effect of predissociation of the N2 Rydberg series R(C) 1Σ+u states by non-Rydberg doubly excited resonances (NRDERs), while nonzero values of circular polarization allow us to unambiguously identify the presence of a directly excited NRDER with 1Π …

Go to article

Transverse Measurements Of Polarization In Optically Pumped Rb Vapor Cells, J. M. Dreiling, E. B. Norrgard, D. Tupa, Timothy J. Gay Jan 2012

Transverse Measurements Of Polarization In Optically Pumped Rb Vapor Cells, J. M. Dreiling, E. B. Norrgard, D. Tupa, Timothy J. Gay

Timothy J. Gay Publications

We have developed a simple heuristic method for determining the polarization of an optically pumped alkalimetal vapor. A linearly polarized probe beam traverses a vapor cell perpendicular to the pump-beam propagation direction, and the transmitted beam intensity is monitored for orthogonal linear polarizations. As the probe beam is scanned in frequency across the D1 transition, its linear-polarization-dependent transmission can be used as a measure of the atomic orientation of the vapor. We analyze these transmission differences and their dependence on the alkali-metal number density in the vapor.

Go to article

The End Of The Beginning, Fred H. Cate, Christopher Kuner, Christopher Millard, Dan Jerker B. Svantesson Jan 2012

The End Of The Beginning, Fred H. Cate, Christopher Kuner, Christopher Millard, Dan Jerker B. Svantesson

Articles by Maurer Faculty

No abstract provided.

Go to article

The Intricacies Of Independence, Fred H. Cate, Christopher Kuner, Christopher Millard, Dan Jerker B. Svantession Jan 2012

The Intricacies Of Independence, Fred H. Cate, Christopher Kuner, Christopher Millard, Dan Jerker B. Svantession

Articles by Maurer Faculty

No abstract provided.

Go to article

The Challenge Of "Big Data" For Data Protection, Fred H. Cate, Christopher Kuner, Christopher Millard, Dan Jerker B. Svantesson Jan 2012

The Challenge Of "Big Data" For Data Protection, Fred H. Cate, Christopher Kuner, Christopher Millard, Dan Jerker B. Svantesson

Articles by Maurer Faculty

No abstract provided.

Go to article

First Prev Next Last