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Physics

2003

Selected Works

Articles 1 - 13 of 13

Full-Text Articles in Physical Sciences and Mathematics

Magnetic And Transport Properties Of The V2– Vi3 Diluted Magnetic Semiconductor Sb2_Xmnxte3, Jeffrey Dyck, P. Svanda, P. Lostak, J. Horak, W. Chen, C. Uher Dec 2003

Magnetic And Transport Properties Of The V2– Vi3 Diluted Magnetic Semiconductor Sb2_Xmnxte3, Jeffrey Dyck, P. Svanda, P. Lostak, J. Horak, W. Chen, C. Uher

Jeffrey Dyck

We have measured electrical and magnetic properties of single crystals of Sb2_xMnxTe3 with x =0 – 0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie–Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn2+ state with S=5/2. Contrary to the case of III–V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V2– VI3 diluted magnetic semiconductors, at least in the range of …

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Light Propagation In Variable-Refractive-Index Materials With Liquid-Crystal-Infiltrated Microcavities, Bin Wang, Philip Bos, Charles D. Hoke Oct 2003

Light Propagation In Variable-Refractive-Index Materials With Liquid-Crystal-Infiltrated Microcavities, Bin Wang, Philip Bos, Charles D. Hoke

Philip J. Bos

A liquid-crystal-infiltrated microcavity structure is proposed as a variable-refractive-index material. It has the advantages over previously considered nanostructured materials of having a larger phase-angle change and lower driving voltage. Two-dimensional liquid-crystal director and finite-difference time-domain optical simulations are used to select liquid crystal material parameters and optimize the dimension of the microcavity structured material.

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Spectral Representation Of The Electrical Properties Of Layered Materials., Anthony Day, A. Mcgurn, D. Bergman, M. Thorpe Sep 2003

Spectral Representation Of The Electrical Properties Of Layered Materials., Anthony Day, A. Mcgurn, D. Bergman, M. Thorpe

Anthony Roy Day

We present a spectral representation for the effective conductivity of two homogeneous layers joined at a rough interface. This spectral representation is closely related to the Bergman-Milton spectral representation for bulk composites, and is easily extended to multilayered materials. By comparing the layered system to a reference layered system that has a flat interface, we form a surface spectral density that captures all the effects of surface structure on the effective conductivity of the layered sample, and is independent of the conductivities of the two layers. Because of the anisotropy of the layered system there are two surface spectral densities, …

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Effect Of Parallel Velocity Shear On The Electrostatic Ion-Cyclotron Instability In Flamentary Current Channels, Erick Agrimson, Su-Hyun Kim, Nicola D'Angelo, Robert L. Merlino Sep 2003

Effect Of Parallel Velocity Shear On The Electrostatic Ion-Cyclotron Instability In Flamentary Current Channels, Erick Agrimson, Su-Hyun Kim, Nicola D'Angelo, Robert L. Merlino

Erick Agrimson

No abstract provided.

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Femtosecond Phase-Coherent Two-Dimensional Spectroscopy, Peifang Tian, Dorine Keusters, Yoshifumi Suzaki, Warren S. Warren May 2003

Femtosecond Phase-Coherent Two-Dimensional Spectroscopy, Peifang Tian, Dorine Keusters, Yoshifumi Suzaki, Warren S. Warren

Peifang Tian

Femtosecond phase-coherent two-dimensional (2D) spectroscopy has been experimentally demonstrated as the direct optical analog of 2D nuclear magnetic resonance. An acousto-optic pulse shaper created a collinear three-pulse sequence with well-controlled and variable interpulse delays and phases, which interacted with a model atomic system of rubidium vapor. The desired nonlinear polarization was selected by phase cycling (coadding experimental results obtained with different interpulse phases). This method may enhance our ability to probe the femtosecond structural dynamics of macromolecules.

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Effect Of Sn Substituting For Sb On The Low-Temperature Transport Properties Of Ytterbium-Filled Skutterudites, J. Yang, D. Morelli, G. Meisner, W. Chen, Jeffrey Dyck, C. Uher Apr 2003

Effect Of Sn Substituting For Sb On The Low-Temperature Transport Properties Of Ytterbium-Filled Skutterudites, J. Yang, D. Morelli, G. Meisner, W. Chen, Jeffrey Dyck, C. Uher

Jeffrey Dyck

We examine the effect of alloying Sn on the Sb site of ytterbium-filled skutterudites, a promising class of thermoelectric materials. We report measurements of the Hall effect, electrical resistivity, Seebeck coefficient, and thermal conductivity between 2 and 300 K on two series of samples having different ytterbium filling fractions: Yb0.19Co4Sb12-xSnx, with x=0, 0.05, 0.1, and 0.2, and Yb0.5Co4Sb12-xSnx, with x=0.5, 0.6, 0.8, 0.83, and 0.9. We find that the substitution of Sn does not lower the electron concentration of these samples, but rather gives rise to a p-type carrier. Hall measurement data for Yb0.5Co4Sb11.17Sn0.83 can be understood in the context …

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Ultrafast Two-Photon Free Induction Decay, D. Keusters, Peifang Tian, W. Warren Dec 2002

Ultrafast Two-Photon Free Induction Decay, D. Keusters, Peifang Tian, W. Warren

Peifang Tian

No abstract provided.

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A Comparison Of Semi-Analytical And Numerical Solutions For The Microwave Heating Of A Lossy Material In A Three-Dimensional Waveguide, Prof. Tim Marchant Dec 2002

A Comparison Of Semi-Analytical And Numerical Solutions For The Microwave Heating Of A Lossy Material In A Three-Dimensional Waveguide, Prof. Tim Marchant

Tim Marchant

The microwave heating of a three-dimensional block in an infinitely long rectangular waveguide propagating the TE10 mode is considered. The electrical conductivity (the dielectric loss) is assumed to be a function of temperature, and modelled by the Arrhenius law. A coupled set of equations is obtained that describes the electromagnetic fields and the temperature distribution in the block. The numerical solutions of this problem are obtained by two methods, the well known FD-TD scheme and a frequency domain method which makes the further assumption that a single TE10 mode exists in the waveguide and material. The results show that an …

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Micro Thermoelectric Cooler Fabrication: Growth And Characterization Of Patterned Sb2te3 And Bi2te3 Films ., Luciana Da Silva, M. Kaviany, A. Dehennis, Jeffrey Dyck Dec 2002

Micro Thermoelectric Cooler Fabrication: Growth And Characterization Of Patterned Sb2te3 And Bi2te3 Films ., Luciana Da Silva, M. Kaviany, A. Dehennis, Jeffrey Dyck

Jeffrey Dyck

A column-type micro thermoelectric cooler is being fabricated using p-type Sb2Te3 and n-type Bi2Te3 films (approximately 4 μm thick). The films are grown by thermal co-evaporation and patterned on Cr/Au/Ti/Pt (hot) connectors, which are deposited onto a silicon dioxide coated wafer. The column height is limited by control of the Te deposition rate. Although a high substrate temperature during thermoelectric film deposition is desired, it has been limited by the degradation of the photoresist used for patterning. The measured Seebeck coefficient and electrical resistivity of the thermoelectric films are reported, and preliminary results show that excess tellurium increases the Seebeck …

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Femtosecond Pulse Shaping Approaches To Multiphoton Imaging., W. Warren, W. Wagner, Peifang Tian, T. Ye Dec 2002

Femtosecond Pulse Shaping Approaches To Multiphoton Imaging., W. Warren, W. Wagner, Peifang Tian, T. Ye

Peifang Tian

No abstract provided.

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Transport Coefficients Of Titanium-Doped Sb2te3 Crystals., P. Svanda, P. LošŤÁK, Č. Drašar, Jeffrey Dyck Dec 2002

Transport Coefficients Of Titanium-Doped Sb2te3 Crystals., P. Svanda, P. LošŤÁK, Č. Drašar, Jeffrey Dyck

Jeffrey Dyck

Titanium-doped single crystals (cTi = 0 to 2×1020 atoms cm-3) were prepared from the elements Sb, Ti, and Te of 5N purity by a modified Bridgman method. The obtained crystals were characterized by measurements of the temperature dependence of the electrical resistivity, Hall coefficient, Seebeck coefficient and thermal conductivity in the temperature range of 5-300 K. It was observed that with an increasing Ti content in the samples the electrical resistance, the Hall coefficient and the Seebeck coefficient increase. This means that the incorporation of Ti atoms into the Sb2Te3 crystal structure results in a decrease in the concentration of …

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Novel Examples Of Achiral Bent-Core Azo Compounds Exhibiting B1 And Anticlinic-Antiferroelectric B2 Mesophases, Veena Prasad, Shin-Woong Kang, Satyendra Kumar Dec 2002

Novel Examples Of Achiral Bent-Core Azo Compounds Exhibiting B1 And Anticlinic-Antiferroelectric B2 Mesophases, Veena Prasad, Shin-Woong Kang, Satyendra Kumar

Satyendra Kumar

The first examples of achiral bent-core molecules consisting of an azo linkage and five aromatic rings exhibiting bent-core mesophases are reported. They exhibit B1 and B2 phases as identified by optical microscopy, differential scanning calorimetry, X-ray diffraction, and electro-optical techniques. The B2 phase of these materials is identified to be the anticlinic–antiferroelectric, SmCAPA phase. The mesophases of these compounds have relatively low transition temperatures and wide temperature ranges. The observation of bent-core phases in azo compounds assumes significance from the fact that the introduction of the –NN– linkage adds a new dimension, namely photochromism, to this field.

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Connection Between Adam-Gibbs Theory And Spatially Heterogeneous Dynamics, N. Giovambattista, S. V. Buldyrev, Francis W. Starr, H. E. Stanley Dec 2002

Connection Between Adam-Gibbs Theory And Spatially Heterogeneous Dynamics, N. Giovambattista, S. V. Buldyrev, Francis W. Starr, H. E. Stanley

Francis Starr

No abstract provided.

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