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Physics

Condensed matter

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Displaying 1001 - 1025 of 1237

Characterization of Soluble Anthradithiophene Derivatives

March 18, 2010
Author(s)
Brad Conrad, Calvin Chan, Marsha A. Loth, John E. Anthony, David J. Gundlach
We will discuss the growth and electrical measurements of a newly developed, partially fluorinated anthradithiophene (F-ADT) derivative with tert-butyldiphenylsilyl (TBDMS) side groups. Single crystals of the material can be readily grown and device hole

Vertically Graded Anisotropy in Co/Pd Multilayers

March 8, 2010
Author(s)
Brian J. Kirby, Joseph E. Davies, Kai Liu, Shannon Watson, G. T. Zimanyi, Robert D. Shull, Paul A. Kienzle, Julie A. Borchers
It has been theoretically predicted that depth-grading the magnetic anisotropy in perpendicular magnetic media should reduce the field required to write data, without affecting the thermal stability. To study this prediction, we have produced a series of

Energy dissipation of highly charged ions on Al oxide films

March 3, 2010
Author(s)
Joshua M. Pomeroy, Russell Lake, C E. Sosolik
Slow highly charged ions carry a large amount of potential energy that can be dissipated within femtoseconds upon interaction with a surface. HCI-insulator collisions result in high sputter yields and surface nano-feature creation due to strong coupling

Normal-state conductance used to probe superconducting tunnel junctions for quantum computing

March 3, 2010
Author(s)
David P. Pappas, Jeffrey S. Kline, Seongshik Ohy, Carlos Chapraro, Richard Bavier, Yong Kim, Eunyoung Kim
Here we report normal-state conductance measurements of three different types of superconducting tunnel junctions that are being used or proposed for quantum computing applications: p-Al/a-AlO/p-Al, e-Re/e-AlO/p-Al, and e-V/e-MgO/p-V, where p stands for

Coexisting Magnetic Order and Cooperative Paramagnetism in the Stuffed Pyrochlore Tb 2+x Ti 2-2x Nb x O 7

February 18, 2010
Author(s)
Benjamin Ueland, Jason S. Gardner, A. J. Williams, M. L. Dahlberg, J.G. Kim, Yiming Qiu, John R. Copley, P. Schiffer, R J. Cava
Neutron scattering and magnetization measurements have been performed on the stuffed pyrochlore system Tb 2+xTi 2-2xNb xO 7. We find that despite the introduction of chemical disorder and increasingly antiferromagnetic interactions, cooperative

Optimization of spin-valve parameters for magnetic bead trapping and manipulation

February 6, 2010
Author(s)
Wendy R. Altman, John M. Moreland, Stephen E. Russek, Victor M. Bright
Magneto-optic Kerr effect (MOKE) and magnetoresistance (MR) measurements were used to measure the switching characteristics of spin-valve (SV) arrays currently being developed to trap and release superparamagnetic beads within a fluid medium. The effect of

Spin-transfer dynamics in spin valves with out-of-plane magnetized CoNi free layers

January 29, 2010
Author(s)
William H. Rippard, Alina M. Deac, Matthew R. Pufall, Justin M. Shaw, Mark W. Keller, Stephen E. Russek, Gerrit E. Bauer, Claudio Serpico
We have measured spin-transfer-induced dynamics in magnetic nanocontact devices having a perpendicularly magnetized Co/Ni free layer and an in-plane magnetized CoFe fixed layer. The frequencies and powers of the excitations agree well with the predictions

Phase Diagram of Magnetic Nanodisks measured by SEMPA

January 20, 2010
Author(s)
Seok-Hwan Chung, Robert D. McMichael, Daniel T. Pierce, John Unguris
We use Scanning Electron Microscopy with Polarization Analysis (SEMPA) to image the magnetic domain structures of individual ferromagnetic nanodisks with different diameters and thicknesses, and thereby determine the phase diagram of the magnetic ground

Many-Pole Model of Inelastic Losses Applied to Calculations of XANES

December 16, 2009
Author(s)
Eric L. Shirley, Joshua J. Kas, J. T. Vinson, N. Trcera, D. Cabaret, John J. Rehr
Conventional Kohn-Sham band-structure methods for calculating deep-core x-ray spectra typically neglect photo-electron self-energy effects, which give rise to an energy dependent shift and broadening of the spectra. Here an a posteriori procedure is

Ultrafast Demagnetization Dynamics at the M Edges of Magnetic Elements Observed Using a Tabletop High-Harmonic Soft X-Ray Source

December 15, 2009
Author(s)
Thomas J. Silva, Justin Shaw, Hans Nembach, Chan La-O-Vorakiat, Mark Siemens, Margaret M. Murnane, Henry C. Kapteyn, Stefan Mathias, Martin Aeschlimann, Patrik Grychtol, Roman Adam, Claus M. Schneider
We use few-femtosecond soft x-ray pulses from high-harmonic generation to extract element-specific demagnetization dynamics and hysteresis loops of a compound material for the first time. Using a geometry where high-harmonic beams are reflected from a

The effect of strain on grains and grain boundaries in YBa2Cu3O7-d coated conductors

December 9, 2009
Author(s)
Daniel C. van der Laan, John (Jack) W. Ekin, Timothy J. Haugan, Paul N. Barnes, Dmytro Abraimov, Fumitake Kametani, David C. Larbalestier, Marty Rupich
The role of grains and grain boundaries in producing reversible strain effects on the transport current critical current (Ic) of YBa2Cu3O7-δ coated conductors was investigated by comparing the strain ε dependence of full-width coated conductors with that

Electrical Characterization of Soluble Anthradithiophene Derivatives

November 19, 2009
Author(s)
Brad Conrad, Calvin Chan, Marsha A. Loth, John E. Anthony, David J. Gundlach
Organic semiconductors remain an active subject for device physics and material science because of their varied electrical properties and potential for low-cost, high-throughput roll-to-roll processing. Several high-mobility oligomers, such as pentacene

Effect of Surface Modes on Photon Propagation through Dielectric Bandgaps

October 28, 2009
Author(s)
Natalia Malkova, Sergey V. Polyakov, Alan L. Migdall, Garnett W. Bryant
We investigate the Hartman saturation effect of photons traveling through barriers created by bandgaps of multilayer stacks. In particular, we investigate theoretically the recently observed jumps in photon transversal times due to adding a single layer

Energy Decay in Josephson Qubits from Non-equilibrium Quasiparticles

August 26, 2009
Author(s)
Jose A. Aumentado, John M. Martinis, M Ansmann
We calculate the energy decay rate of Josephson qubits and superconducting resonators from non-equilibrium quasiparticles. The decay rates from experiments are shown to be consistent with our predictions based on a prior measurement of the quasiparticle

Coupled magnetic and ferroelectric hysteresis in multiferroic Ni ^ d3 ^ V ^ d2 ^ O ^ d8 ^

August 18, 2009
Author(s)
I. Cabrera, M. Kenzelmann, Wangchun Chen, Ross Erwin, Thomas R. Gentile, Juscelino Leao, Jeffrey W. Lynn, N. Rogado, R. J. Cava, C. Broholm, G. Lawes, Ying Chen
Electric control of spin chirality in a magnetically frustrated multiferroic is demonstrated through polarized magnetic neutron diffraction. Cooling to the cycloidal multiferroic phase of Ni ^ d3 ^ V ^ d2 ^ O ^ d8 ^ in an electric field causes the

Anomalous thermal behavior in microcalorimeter gamma-ray detectors

July 20, 2009
Author(s)
Robert D. Horansky, James A. Beall, Kent D. Irwin, Joel N. Ullom
Improving the resolution of gamma-ray detectors is important for many fields, including determinations of the Lamb shift in atoms with high atomic numbers , nuclear treaty verification , and environmental monitoring. High-purity germanium detectors are

The-Final-State Symmetry of Na 1s Core-shell Excitons in NaCl and NaF

July 8, 2009
Author(s)
Eric L. Shirley, K. P. Nagle, G T. Seidler, T. T. Fister, J. A. Bradley, F. C. Brown
We report measurements of the Na 1s contribution to the nonresonant inelastic x-ray scattering (NRIXS) from NaCl and NaF. Prior x-ray absorption studies have observed two pre-edge excitons in both materials. The momentum transfer-dependence (q-dependence)

Inter-Laboratory Comparisons of NbTi Critical Current Measurements

June 22, 2009
Author(s)
Arno Godeke, D. Turrioni, T. Boutboul, Najib Cheggour, A. K. Ghosh, Loren F. Goodrich, M Meinesz, A. den Ouden
We report on a multi-institute comparison of critical current data, measured on a modern Large Hadron Collider (LHC) NbTi wire that has shown a standard deviation below 1% in critical current density spread in more than 1500 measurements. Inter-laboratory

Internal tin Nb3Sn conductors engineered for fusion and particle accelerator applications

June 22, 2009
Author(s)
Jeffrey Parrell, Y. Zhang, Michael Field, M Meinesz, Yonghua Huang, H Miao, Seungok Hong, Najib Cheggour, Loren F. Goodrich
The critical current density (Jc) of Nb3Sn strand has been significantly improved over the last several years. For most magnet applications, high Jc internal tin has displaced bronze process strand. The highest Jc values are obtained from distributed

Number Fluctuations and Energy Dissipation in Sodium Spinor Condensates

June 5, 2009
Author(s)
Yingmei Liu, Eduardo N. Gomez, Stephen E. Maxwell, Lincoln D. Turner, Eite Tiesinga, Paul D. Lett
We characterize fluctuations in atom number and spin populations in F = 1 sodium spinor condensates. The time evolution of the population fluctuations shows a maximum. We interpret this as evidence of a dissipation-driven separatrix crossing in phase space
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