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University of Nebraska - Lincoln

2007

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Articles 1 - 30 of 139

Full-Text Articles in Physics

Observation Of P-Wave Threshold Behavior In Electron Attachment To F2 Molecules, M. Braun, M.-W. Ruf, Ilya I. Fabrikant, H. Hotop Dec 2007

Observation Of P-Wave Threshold Behavior In Electron Attachment To F2 Molecules, M. Braun, M.-W. Ruf, Ilya I. Fabrikant, H. Hotop

Ilya Fabrikant Publications

Using the high resolution laser photoelectron attachment method, we demonstrate that the cross section for F- formation due to electron capture by F2 (X1Σg+) molecules at very low energies exhibits p-wave threshold behavior. This finding confirms the theoretical expectation that low-energy attachment to F2 proceeds through the F2-(2 Σu+) p-wave shape resonance in contrast with previous experimental claims for s-wave threshold behavior.


Measurement Of The Pp̅Wz + X Cross Section At √S =1.96 Tev And Limits On Wwz Trilinear Gauge Couplings, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Dec 2007

Measurement Of The Pp̅ → Wz + X Cross Section At √S =1.96 Tev And Limits On Wwz Trilinear Gauge Couplings, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We present measurements of the process pp̅WZ + X → ℓ′νℓℓ&#; at √s = 1.96 TeV, where ℓ and ℓ′ are electrons or muons. Using 1 fb-1 of data from the D0 experiment, we observe 13 candidates with an expected background of 4.5 ± 0.6 events and measure a cross section σ(WZ) = 2.7-1.3+1.7 pb. From the number of observed events and the Z boson transverse momentum distribution, we limit the trilinear WWZ gauge couplings to -0.17 ≤ λZ ≤ 0.21(ΔκZ= 0) at the 95% C.L. for a form ...


Ultrashort Intense-Field Optical Vortices Produced With Laser-Etched Mirrors, James Strohaber, Timothy D. Scarborough, Cornelis J. Uiterwaal Dec 2007

Ultrashort Intense-Field Optical Vortices Produced With Laser-Etched Mirrors, James Strohaber, Timothy D. Scarborough, Cornelis J. Uiterwaal

C.J.G.J. Uiterwaal Publications

We introduce a simple and practical method to create ultrashort intense optical vortices for applications involving high-intensity lasers. Our method utilizes femtosecond laser pulses to laser etch grating lines into laser-quality gold mirrors. These grating lines holographically encode an optical vortex. We derive mathematical equations for each individual grating line to be etched, for any desired (integer) topological charge. We investigate the smoothness of the etched grooves. We show that they are smooth enough to produce optical vortices with an intensity that is only a few percent lower than in the ideal case. We demonstrate that the etched gratings can ...


Study Of The Decay BS0DS(*)DS(*), V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Dec 2007

Study Of The Decay BS0 → DS(*)DS(*), V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We report a study of the decay Bs0Ds(*)Ds(*) using a data sample corresponding to 1.3 fb-1 of integrated luminosity collected by the D0 experiment in 2002–2006 during run II of the Fermilab Tevatron collider. One Ds(*) meson was partially reconstructed in the decay Ds→ φμν, and the other Ds(*) meson was identified using the decay Ds→ φπ where no attempt was made to distinguish Ds and Ds(*) states. For the branching fraction Br(Bs0Ds(*)Ds(*)) we obtain a 90% C ...


Identification Of The Possible Defect States In Poly(3-Hexylthiophene) Thin Films, D.-Q. Feng, A. N. Caruso, Yaroslav B. Losovyj, D. L. Schulz, Peter A. Dowben Dec 2007

Identification Of The Possible Defect States In Poly(3-Hexylthiophene) Thin Films, D.-Q. Feng, A. N. Caruso, Yaroslav B. Losovyj, D. L. Schulz, Peter A. Dowben

Peter Dowben Publications

The possible origins of a low density of defect states within the highest occupied molecular orbital to lowest unoccupied molecular orbital gap are suggested for regioregular poly(3- hexylthiophene). A number of chemical defects, impurities, and structural defects could contribute to features in photoemission for regioregular poly(3-hexylthiophene), observed within the highest occupied molecular orbital to lowest unoccupied molecular orbital gap of regioregular poly(3-hexylthiophene).


Characterization Of Metalferroelectric-Insulator-Semiconductor Structures Based On Ferroelectric Langmuir-Blodgett Polyvinylidene Fluoride Copolymer Films For Nondestructive Random Access Memory Applications, Timothy J. Reece Dec 2007

Characterization Of Metalferroelectric-Insulator-Semiconductor Structures Based On Ferroelectric Langmuir-Blodgett Polyvinylidene Fluoride Copolymer Films For Nondestructive Random Access Memory Applications, Timothy J. Reece

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

Ferroelectric field effect transistors (FeFETs) have attracted much attention recently because of their ability to combine high speed, low power consumption, and fast nondestructive readout with the potential for high density nonvolatile memory. The polarization of the ferroelectric is used to switch the channel at the silicon surface between states of high and low conductance.

Among the ferroelectric thin films used in FET devices; the ferroelectric copolymer of Polyvinylidene fluoride, PVDF (C2H2F2), with trifluoroethylene, TrFE (C2HF3), has distinct advantages, including low dielectric constant, low processing temperature, low cost and compatibility with organic ...


Measurement Of The Tt̅ Production Cross Section In Pp̅ Collisions At √S = 1.96 Tev Using Kinematic Characteristics Of Lepton + Jets Events, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Nov 2007

Measurement Of The Tt̅ Production Cross Section In Pp̅ Collisions At √S = 1.96 Tev Using Kinematic Characteristics Of Lepton + Jets Events, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We present a measurement of the top quark pair production cross section in pp̅ collisions at √s = 1.96 TeV utilizing 425 pb-1 of data collected with the D0 detector at the Fermilab Tevatron Collider. We consider the final state of the top quark pair containing one high-pT electron or muon and at least four jets. We exploit specific kinematic features of tt̅ events to extract the cross section. For a top quark mass of 175 GeV, we measure σ tt̅ = 6.4-1.2+1.3(stat) ± 0.7(syst) ± 0.4(lum) pb, in good ...


High-Resolution Photoemission Study Of Organic Systems At The Camd 3 M Nim Beamline, Yaroslav B. Losovyj, Kevin Morris, Luis G. Rosa, John D. Scott, Peter A. Dowben Nov 2007

High-Resolution Photoemission Study Of Organic Systems At The Camd 3 M Nim Beamline, Yaroslav B. Losovyj, Kevin Morris, Luis G. Rosa, John D. Scott, Peter A. Dowben

Peter Dowben Publications

The 3 m normal incidence monochromator (NIM) VUV beamline at CAMD was designed for novel high-resolution photoemission experiments. Both solid-state samples and gas phase resolution tests demonstrate that high-resolution photoemission is possible below 10 meV, and vibronic fine structure in the photoemission final state from the crystalline copolymer poly-vinylidene fluoride with trifluoroethylene can be observed: the first direct experimental identification of symmetry dependence in electron–phonon coupling in photoemission from a solid-state system.


Optimization Of The 3 M Tgm Beamline, At Camd, For Constant Initial State Spectroscopy, Yaroslav B. Losovyj, Ihor Ketsman, Eizi Morikawa, Zhenjun Wang, Jinke Tang, Peter A. Dowben Nov 2007

Optimization Of The 3 M Tgm Beamline, At Camd, For Constant Initial State Spectroscopy, Yaroslav B. Losovyj, Ihor Ketsman, Eizi Morikawa, Zhenjun Wang, Jinke Tang, Peter A. Dowben

Peter Dowben Publications

The 3 m toroidal grating monochromator (TGM) VUV beamline at CAMD/LSU was realigned to achieve better illumination of the monochromator gratings with the goal of substantially increasing the flux at the higher photon energies. This is partly accomplished through a tilting of the monochromator (by about of 13.5°), with respect to the plane defined by the synchrotron, providing a smaller grazing angle at the initial mirrors. The improved performance of the beamline permits resonant photoemission studies at Gd 4d core threshold without resorting to second order light, which we demonstrate for Gd doped HfO2.


Search For Production Of Single Top Quarks Via Tcg And Tug Flavor-Changing-Neutral-Current Couplings, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Nov 2007

Search For Production Of Single Top Quarks Via Tcg And Tug Flavor-Changing-Neutral-Current Couplings, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We search for the production of single top quarks via flavor-changing-neutral-current couplings of a gluon to the top quark and a charm (c) or up (u) quark. We analyze 230 pb-1 of lepton + jets data from pp̅ collisions at a center of mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We observe no significant deviation from standard model predictions, and hence set upper limits on the anomalous coupling parameters κgc/Λ and κgu/Λ, where κg define the strength of tcg and tug couplings, and Λ ...


Correlation Of The Highest-Energy Cosmic Rays With Nearby Extragalactic Objects, J. Abraham, Gregory Snow, Pierre Auger Collaboration Nov 2007

Correlation Of The Highest-Energy Cosmic Rays With Nearby Extragalactic Objects, J. Abraham, Gregory Snow, Pierre Auger Collaboration

Gregory Snow Publications

Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 × 1019 electron volts and the positions of active galactic nuclei (AGN) lying within ~75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these cosmic rays with at least a 99% confidence level from a prescribed a priori test. The correlation we observed is compatible with the hypothesis that the highest-energy particles originate from nearby extragalactic sources whose flux has not been substantially reduced by interaction with the cosmic ...


Search For Production Of Single Top Quarks Via Tcg And Tug Flavor-Changing-Neutral-Current Couplings, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Nov 2007

Search For Production Of Single Top Quarks Via Tcg And Tug Flavor-Changing-Neutral-Current Couplings, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We search for the production of single top quarks via flavor-changing-neutral-current couplings of a gluon to the top quark and a charm (c) or up (u) quark. We analyze 230 pb-1 of lepton + jets data from pp̅ collisions at a center of mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We observe no significant deviation from standard model predictions, and hence set upper limits on the anomalous coupling parameters Kgc/ Λ and Kgu/ Λ, where Kg define the strength of tcg and tug couplings, and Λ defines the scale of new physics ...


Search For Production Of Single Top Quarks Via Tcg And Tug Flavor-Changing-Neutral-Current Couplings, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Nov 2007

Search For Production Of Single Top Quarks Via Tcg And Tug Flavor-Changing-Neutral-Current Couplings, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We search for the production of single top quarks via flavor-changing-neutral-current couplings of a gluon to the top quark and a charm (c) or up (u) quark. We analyze 230 pb-1 of lepton + jets data from pp̅ collisions at a center of mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We observe no significant deviation from standard model predictions, and hence set upper limits on the anomalous coupling parameters Kgc/ Λ and Kgu/ Λ, where Kg define the strength of tcg and tug couplings, and Λ defines ...


Search For Production Of Single Top Quarks Via Tcg And Tug Flavor-Changing-Neutral-Current Couplings, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Nov 2007

Search For Production Of Single Top Quarks Via Tcg And Tug Flavor-Changing-Neutral-Current Couplings, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We search for the production of single top quarks via flavor-changing-neutral-current couplings of a gluon to the top quark and a charm (c) or up (u) quark. We analyze 230 pb-1 of lepton + jets data from pp̅ collisions at a center of mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We observe no significant deviation from standard model predictions, and hence set upper limits on the anomalous coupling parameters Kgc/ Λ and Kgu/ Λ, where Kg define the strength of tcg and tug couplings, and Λ defines ...


Search For A Higgs Boson Produced In Association With A Z Boson In Pp̅ Collisions, V. M. Abazov, Kenneth A. Bloom, Gregory Snow Nov 2007

Search For A Higgs Boson Produced In Association With A Z Boson In Pp̅ Collisions, V. M. Abazov, Kenneth A. Bloom, Gregory Snow

Gregory Snow Publications

We describe a search for the Standard Model Higgs boson with a mass of 105 GeV/c2 to 145 GeV/c2 in data corresponding to an integrated luminosity of approximately 450 pb-1 collected with the DØ detector at the Fermilab Tevatron p̅p collider at a center-of-mass energy of 1.96 TeV. The Higgs boson is required to be produced in association with a Z boson, and the Z boson is required to decay to either electrons or muons with the Higgs boson decaying to a b̅b pair. The data are well described by the expected ...


Measurement Of The ΛB0 Lifetime Using Semileptonic Decays, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Nov 2007

Measurement Of The ΛB0 Lifetime Using Semileptonic Decays, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We report a measurement of the Λb0 lifetime using a sample corresponding to 1:3 fb-1 of data collected by the D0 experiment in 2002–2006 during run II of the Fermilab Tevatron collider. The Λb0 baryon is reconstructed via the decay Λb0 → μν&#; Λ c+X. Using 4437 ± 329 signal candidates, we measure the Λb0 lifetime to be τ(Λb0) = 1.290-0.110+0.119 (stat) -0.091+0.087(syst) ps, which is among the most precise measurements in semileptonic Λb0 decays. This result ...


Measurement Of The ΛB0 Lifetime Using Semileptonic Decays, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Nov 2007

Measurement Of The ΛB0 Lifetime Using Semileptonic Decays, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We report a measurement of the Λb0 lifetime using a sample corresponding to 1.3 fb-1 of data collected by the D0 experiment in 2002–2006 during run II of the Fermilab Tevatron collider. The Λb0 baryon is reconstructed via the decay Λb0 → μν̅Λc+ X. Using 4437 ± 329 signal candidates, we measure the Λb0 lifetime to be τ(Λb0) = 1.290-0.110+0.119 (stat) -0.091+0.087 (syst) ps, which is among the most precise measurements in semileptonic Λb0 decays. This result ...


Agn Reddening And Ultraviolet Extinction Curves From Hubble Space Telescope Spectra, C. Martin Gaskell, C. Martin Gaskell Nov 2007

Agn Reddening And Ultraviolet Extinction Curves From Hubble Space Telescope Spectra, C. Martin Gaskell, C. Martin Gaskell

Martin Gaskell Publications

We present intrinsic extinction curves for 14 AGNs. The AGNs have reddenings, E(B-V), of up to 0.36 mag. The majority (13 out of 14) of the extinction curves are not steep in the UV. Of the seven best determined extinction curves, five have extinction curves that are as flat as the standard Galactic curve in the optical and near UV, but flatter in the far UV, and without the λ2175 feature. One AGN, B3 0754+394, has a steep SMC-like extinction curve, and another, Mrk 304, has an LMC-like extinction curve, including a probable λ2175 bump. The remaining ...


Discovery Of Polarization Reverberation In Ngc 4151, C. Martin Gaskell, René W. Goosmann, Nelly I. Merkulova, Nikolay M. Shakhovskoy, Masatoshi Shoji Nov 2007

Discovery Of Polarization Reverberation In Ngc 4151, C. Martin Gaskell, René W. Goosmann, Nelly I. Merkulova, Nikolay M. Shakhovskoy, Masatoshi Shoji

Martin Gaskell Publications

Observations of the optical polarization of NGC 4151 in 1997–2003 show variations of an order of magnitude in the polarized flux while the polarization position angle remains constant. The amplitude of variability of the polarized flux is comparable to the amplitude of variability of the total U-band flux, except that the polarized flux follows the total flux with a lag of 8±3 days. The time lag and the constancy of the position angle strongly favor a scattering origin for the variable polarization rather than a non-thermal synchrotron origin. The orientation of the position angle of the polarized flux ...


The Case For Optically Thick High-Velocity Broad-Line Region Gas In Active Galactic Nuclei, Stephanie A. Snedden, C. Martin Gaskell Nov 2007

The Case For Optically Thick High-Velocity Broad-Line Region Gas In Active Galactic Nuclei, Stephanie A. Snedden, C. Martin Gaskell

Martin Gaskell Publications

A combined analysis of the profiles of the main broad quasar emission lines in both Hubble Space Telescope and optical spectra shows that while the profiles of the strong UV lines are quite similar, there is frequently a strong increase in the Lyα/Hα ratio in the high-velocity gas.We show that the suggestion that the high-velocity gas is optically thin presents many problems.We show that the relative strengths of the high-velocity wings arise naturally in an optically thick BLR component. An optically thick model successfully explains the equivalent widths of the lines, the Lyα/Hα ratios and flatter ...


Half Metallic Ferromagnets, Peter A. Dowben Nov 2007

Half Metallic Ferromagnets, Peter A. Dowben

Peter Dowben Publications

Since its introduction by de Groot and colleagues in the early 1980s [1], the concept of half metallic ferromagnetism has attracted great interest. Idealized, half-metals have only one spin channel for conduction: the spin-polarized band structure exhibits metallic behavior for one spin channel, while the other spin band structure exhibits a gap at the Fermi level. Due to the gap for one spin direction, the density of states at the Fermi level has, theoretically, 100 % spin polarization. This gap in the density of states in one spin at the Fermi level, for example ↓ so N↓(EF) = 0, also causes ...


Bias Voltage Dependence Of Tunneling Anisotropic Magnetoresistance In Magnetic Tunnel Junctions With Mgo And Al2O3 Tunnel Barriers, Li Gao, Xin Jiang, See-Hun Yang, John D. Burton, Evgeny Y. Tsymbal, Stuart S. P. Parkin Nov 2007

Bias Voltage Dependence Of Tunneling Anisotropic Magnetoresistance In Magnetic Tunnel Junctions With Mgo And Al2O3 Tunnel Barriers, Li Gao, Xin Jiang, See-Hun Yang, John D. Burton, Evgeny Y. Tsymbal, Stuart S. P. Parkin

Evgeny Tsymbal Publications

Tunneling anisotropic magnetoresistance (TAMR) is observed in tunnel junctions with transition metal electrodes as the moments are rotated from in-plane to out-of-plane in sufficiently large magnetic fields that the moments are nearly parallel to one another. A complex angular dependence of the tunneling resistance is found with twofold and fourfold components that vary strongly with bias voltage. Distinctly different TAMR behaviors are obtained for devices formed with highly textured crystalline MgO(001) and amorphous Al2O3 tunnel barriers. A tight-binding model shows that a fourfold angular dependence can be explained by the presence of an interface resonant state ...


Harmonic Holography: A New Holographic Principle, Ye Pu, Martin Centurion, Demetri Psaltis Nov 2007

Harmonic Holography: A New Holographic Principle, Ye Pu, Martin Centurion, Demetri Psaltis

Martin Centurion Publications

The process of second harmonic generation (SHG) has a unique property of forming a sharp optical contrast between noncentrosymmetric crystalline materials and other types of material, which is a highly valuable asset for contrast microscopy. The coherent signal obtained through SHG also allows for the recording of holograms at high spatial and temporal resolution, enabling whole-field four-dimensional microscopy for highly dynamic microsystems and nanosystems. Here we describe a new holographic principle, harmonic holography (H2), which records holograms between independently generated second harmonic signals and reference. We experimentally demonstrate this technique with digital holographic recording of second harmonic signals upconverted ...


Transformations Between 2mass, Sdss And Bvri Photometric Systems: Bridging The Near Infrared And Optical, S. Bilir, S. Ak, S. Karaali, A. Cabrera-Lavers, T. S. Chonis, C. Martin Gaskell Nov 2007

Transformations Between 2mass, Sdss And Bvri Photometric Systems: Bridging The Near Infrared And Optical, S. Bilir, S. Ak, S. Karaali, A. Cabrera-Lavers, T. S. Chonis, C. Martin Gaskell

Martin Gaskell Publications

We present color transformations for the conversion of the 2MASS photometric system to the Johnson-Cousins UBV RI system and further into the SDSS ugriz system. We have taken SDSS gri magnitudes of stars measured with the 2.5-m telescope from SDSS Data Release 5 (DR5), and BV RI and JHKs magnitudes from Stetson’s catalogue and Cutri et al. (2003), respectively. We matched thousands of stars in the three photometric systems by their coordinates and obtained a homogeneous sample of 825 stars by the following constraints, which are not used in previous transformations: 1) the data are de-reddened, 2 ...


Ngc 5548: The Agn Energy Budget Problem And The Geometry Of The Broad-Line Region And Torus, C. Martin Gaskell, Elizabeth S. Klimek, Ludmila S. Nazarova Nov 2007

Ngc 5548: The Agn Energy Budget Problem And The Geometry Of The Broad-Line Region And Torus, C. Martin Gaskell, Elizabeth S. Klimek, Ludmila S. Nazarova

Martin Gaskell Publications

We consider in detail the spectral energy distribution (SED) and multi-wavelength variability of NGC 5548. Comparison with the SEDs of other AGNs implies that the internal reddening of NGC 5548 is E(B-V) = 0.17 mag. The extinction curve is consistent with the mean curve of other AGNs found by Gaskell & Benker, but inconsistent with an SMC-type reddening curve. Because most IR emission originates exterior to the broad-line region (BLR), the SED seen by the inner BLR is different from that seen by the outer BLR and from the earth. The most likely BLR covering factor is ~ 40% and it ...


Search For BS0→ Μ+ Μ- Decays At D0, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Nov 2007

Search For BS0→ Μ+ Μ- Decays At D0, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We report results from a search for the decay Bs0 → μ+μ- using 1.3 fb-1 of pp̅ collisions at √s= 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron Collider.We find two candidate events, consistent with the expected background of 1.24 ± 0.99, and set an upper limit on the branching fraction of Ɓ(Bs0 → μ+μ-) < 1.2 x 10-7 at the 95% C.L.


Reversal Of Spin Polarization In Fe/Gaas (001) Driven By Resonant Surface States: First-Principles Calculations, Athanasios N. Chantis, Kirill D. Belashchenko, D. L. Smith, Evgeny Y. Tsymbal, Mark Van Schilfgaarde, R. C. Albers Nov 2007

Reversal Of Spin Polarization In Fe/Gaas (001) Driven By Resonant Surface States: First-Principles Calculations, Athanasios N. Chantis, Kirill D. Belashchenko, D. L. Smith, Evgeny Y. Tsymbal, Mark Van Schilfgaarde, R. C. Albers

Evgeny Tsymbal Publications

A minority-spin resonant state at the Fe/GaAs(001) interface is predicted to reverse the spin polarization with the voltage bias of electrons transmitted across this interface. Using a Green's function approach within the local spin-density approximation, we calculate the spin-dependent current in a Fe/GaAs/Cu tunnel junction as a function of the applied bias voltage. We find a change in sign of the spin polarization of tunneling electrons with bias voltage due to the interface minority-spin resonance. This result explains recent experimental data on spin injection in Fe/GaAs contacts and on tunneling magnetoresistance in Fe/GaAs ...


Isothermal Low-Field Tuning Of Exchange Bias In Epitaxial Fe/Cr2o3/Fe, Sarbeswar Sahoo, Tathagata Mukherjee, Kirill D. Belashchenko, Christian Binek Oct 2007

Isothermal Low-Field Tuning Of Exchange Bias In Epitaxial Fe/Cr2o3/Fe, Sarbeswar Sahoo, Tathagata Mukherjee, Kirill D. Belashchenko, Christian Binek

Christian Binek Publications

Moderate dc magnetic fields of less than 1 T allow tuning the exchange bias in an epitaxially grown Fe 10 nm/Cr2O3 2.7 nm/Fe 10 nm trilayer between negative and positive bias fields. Remarkably, this tunable exchange bias is observed at least up to 395 K which exceeds the Néel temperature of bulk Cr2O3 (307 K). The presence of spontaneous exchange bias and the absence of training effects at room temperature suggest the existence of stable interface moments independent of antiferromagnetic long range order in Cr2O3. Furthermore, the coercivity ...


Ferroelectric Control Of Magnetism In Batio3 /Fe Heterostructures Via Interface Strain Coupling, Sarbeswar Sahoo, Srinivas Polisetty, Chun-Gang Duan, Sitaram S. Jaswal, Evgeny Y. Tsymbal, Christian Binek Oct 2007

Ferroelectric Control Of Magnetism In Batio3 /Fe Heterostructures Via Interface Strain Coupling, Sarbeswar Sahoo, Srinivas Polisetty, Chun-Gang Duan, Sitaram S. Jaswal, Evgeny Y. Tsymbal, Christian Binek

Christian Binek Publications

Reversible control of magnetism is reported for a Fe thin film in proximity of a BaTiO3 single crystal. Large magnetization changes emerge in response to ferroelectric switching and structural transitions of BaTiO3 controlled by applied electric fields and temperature, respectively. Interface strain coupling is the primary mechanism altering the induced magnetic anisotropy. As a result, coercivity changes up to 120% occur between the various structural states of BaTiO3. Up to 20% coercivity change is achieved via electrical control at room temperature. Our all solid state ferroelectric-ferromagnetic heterostructures open viable possibilities for technological applications.


Properties Of L = 1 B1 And B2* Mesons, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Oct 2007

Properties Of L = 1 B1 And B2* Mesons, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

This Letter presents the first strong evidence for the resolution of the excited B mesons B1 and B2* as two separate states in fully reconstructed decays to B+(*). The mass of B1 is measured to be 5720.6 ± 2.4 ± 1.4 MeV=c 2 and the mass difference ΔM between B2* and B1 is 26.2 ± 3.1 ± 0.9 MeV/c 2, giving the mass of the B2* as 5746.8 ± 2.4 ± 1.7 MeV/c 2. The production rate for B1 and B2* mesons is determined to ...