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

Physical Sciences and Mathematics Commons™

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

Physics

Institution
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 33841 - 33870 of 36549

Full-Text Articles in Physical Sciences and Mathematics

Magnetic Properties, Anisotropy, And Microstructure Of Sputtered Rare-Earth Iron Multilayers, Z.S. Shan, S. Nafis, K.D. Aylesworth, David J. Sellmyer Apr 1988

Magnetic Properties, Anisotropy, And Microstructure Of Sputtered Rare-Earth Iron Multilayers, Z.S. Shan, S. Nafis, K.D. Aylesworth, David J. Sellmyer

David Sellmyer Publications

A study of compositionally modulated magnetic films of the form Fe/RE, particularly for RE=Nd and Dy, has been performed by vibrating sample magnetometry, ac susceptibility and x-ray diffraction. The relationship between the magnetic properties and the layer thickness was studied systematically for X-Å Fe/Y-Å Dy, as the layer thicknesses X and Y were varied from 1.8 to 20 Å. The ranges of layer thicknesses required for perpendicular anisotropy were determined. The interface and volume anisotropy energies were estimated for X-Å Fe/Y-Å Nd and the differences in the magnetic properties between X-Å Fe/7-Å Dy and X-Å Fe/7-Å …

Go to article

Coherent Population Trapping In N-Level Quantum Systems, Foek T. Hioe, C. E. Carroll Apr 1988

Coherent Population Trapping In N-Level Quantum Systems, Foek T. Hioe, C. E. Carroll

Physics Faculty/Staff Publications

A multilevel quantum system interacting with an intense laser Seld is shown to exhibit many invariants, or constants of evolution, under various conditions. Our results also apply to other similar physical problems.

Go to article

Ellipsometric And Magneto-Optic Properties Of Sputtered Dysprosium-Iron Multilayers, Thomas E. Tiwald, John A. Woollam, David J. Sellmyer Apr 1988

Ellipsometric And Magneto-Optic Properties Of Sputtered Dysprosium-Iron Multilayers, Thomas E. Tiwald, John A. Woollam, David J. Sellmyer

David Sellmyer Publications

Ellipsometric and magneto-optical properties of Dy (3.5 Å thick) and Fe (2.5–12.5 Å thick) multilayers were investigated over the spectral range from 3000 to 8000 Å in magnetic fields to 0.21 T. In this range of layer thickness the magnetic anisotropy is vertical. Kerr rotations, were found to be weakly spectrally dependent, and as large as 0.06°. The magnetically driven change of ellipticity of reflected light was as large as 0.13, depending on sample and wavelength. Ellipsometric analysis of layer thickness was performed assuming a multilayer geometry. In addition, the optical constants were determined assuming the multilayer was a homogeneous …

Go to article

Magnetic Properties Of Rapidly Quenched And Annealed Fe10Rti And Related Alloys, Z.R. Zhao, Y.G. Ren, K.D. Aylesworth, David J. Sellmyer, E. Singleton, J. Strzeszewski, George C. Hadjipanayis Apr 1988

Magnetic Properties Of Rapidly Quenched And Annealed Fe10Rti And Related Alloys, Z.R. Zhao, Y.G. Ren, K.D. Aylesworth, David J. Sellmyer, E. Singleton, J. Strzeszewski, George C. Hadjipanayis

David Sellmyer Publications

Magnetic measurements are reported for iron-rich ternary alloys with the following compositions: Fe10NdxDy1-xTi (0≤x≤1), Fe10SmM (M=Ti, V, and Mo), and Fe10RV (R=Y, Gd, and Dy). The samples were prepared by splat cooling or melt spinning and selected samples were heat treated. The results of x-ray diffraction, electron microscopy, and thermomagnetic measurements on the Fe10NdxDy1-xTi series are presented and indicate that the rapidly quenched alloys are nearly single phase and become multiphase upon heating. Magnetic measurements on the other two series show that the substitution …

Go to article

Magnetic Transitions And Phases In Random-Anisotropy Magnets, David J. Sellmyer, S. Nafis, Michael J. O'Shea Apr 1988

Magnetic Transitions And Phases In Random-Anisotropy Magnets, David J. Sellmyer, S. Nafis, Michael J. O'Shea

David Sellmyer Publications

The generality and universality of the Ising spin-glass-like phase transitions observed in several rare-earth, random-anisotropy magnets are discussed. Some uncertainties and practical problems in determining critical exponents are considered, and a comparison is made to insulating spin glasses and crystalline spin glasses where an apparent anisotropy-induced crossover from Heisenberg to Ising-like behavior is seen. The observation of a reentrant transition in a weak anisotropy system and its correlation with the theory of Chudnovsky, Saslow, and Serota [Phys. Rev. B 33, 251 (1986)] for the correlated spin glass is discussed. Journal of Applied Physics is copyrighted by The American Institute of …

Go to article

Particle Size Dependence Of The Magnetic Properties Of Ultrafine Granular Films, Sy_Hwang Liou, C.L. Chien Apr 1988

Particle Size Dependence Of The Magnetic Properties Of Ultrafine Granular Films, Sy_Hwang Liou, C.L. Chien

Sy-Hwang Liou Publications

Magnetic granular solids consist of ultrafine metal granules of nanometer sizes embedded in an insulating medium. The magnetic properties are dictated by the microstructure such as particle size, metal volume fraction, which are process controlled. We report the results of a series of granular Fe60(SiO2)40 films in which the particle size has been systematically varied. The magnetic coercivity, ranging from 500 to 2200 Oe, increases with particle size. The ferromagnetic-superparamagnetic transition had been studied by SQUID magnetometry and Mössbauer spectroscopy. The value of the magnetic anisotropy energy is found to be much larger than that …

Go to article

Nonisothermal Relaxation In A Nonlocal Medium, Alexander Umantsev, A L. Roitburd Apr 1988

Nonisothermal Relaxation In A Nonlocal Medium, Alexander Umantsev, A L. Roitburd

Chemistry and Physics Faculty Working Papers

A study is made of the thermodynamics of a non-local medium whose evolution is governed not only by the temperature and pressure, but also by the field of a relaxation parameter. For solid-state materials which undergo a phase transition, such a relaxation parameter is the order parameter. Heat transport equations are derived together with a thermodynamic inequality which must be satisfied during relaxation. The motion of an interphase boundary during a first-order phase transition is investigated. It is shown that, if the width of the boundary exceeds a critical value, there are steady-state conditions under which the new phase formed …

Go to article

Premartensitic Anelasticity In Indium-Thallium Alloys., Manfred Wuttig, C. Y. Lei, Tetsuro Suzuki Apr 1988

Premartensitic Anelasticity In Indium-Thallium Alloys., Manfred Wuttig, C. Y. Lei, Tetsuro Suzuki

Materials Science and Engineering Faculty Research & Creative Works

The linear and nonlinear low frequency internal friction of In-24 at. pct Tl displays a Curie-Weiss type behavior in the temperature range above the transformation temperature. The critical temperature equals the martensite start temperature. It is proposed that the origin of the observed internal friction is the diffusion-controlled interaction of substitutional atoms with the premartensitic strain modulation, tweed.

Go to article

Some Issues Of Thermodynamic Consistency In Binary Nucleation Theory, Gerald Wilemski Apr 1988

Some Issues Of Thermodynamic Consistency In Binary Nucleation Theory, Gerald Wilemski

Physics Faculty Research & Creative Works

The "generalized" Kelvin equations used to determine the critical nucleus composition in some binary nucleation theories are shown to be thermodynamically inconsistent. Also, the surface tension calculated by the method of Flageollet-Daniel, Gamier, and Mirabel [J. Chem. Phys. 78, 2600 (1983)] is shown to be thermodynamically consistent with respect to the dynamic surface tension, contrary to the recent assertion of Spiegel, Zahoransky, and Wittig.

Go to article

Ionization Of K-Shell Electrons By Highly Relativistic Protons, M. L. Rustgi, P.T. Leung, S. A. Long Apr 1988

Ionization Of K-Shell Electrons By Highly Relativistic Protons, M. L. Rustgi, P.T. Leung, S. A. Long

Physics Faculty Publications and Presentations

A comparative study of three decent theoretical formalisms by Anholt, Scofield, Becker, and coworkers (1978-85) for K-shell ionization by highly relativistic protons has been carried out. The importance of the spin-flip mechanism is emphasized. It is concluded that in the analysis of such inner-shell ionization processes, an accurate description of the projectile-target interaction is of much more significance than the accuracy of the wave functions of the atomic electrons.

Go to article

A Study Of An Integral Equations For Computing Radial Distribution Functions, Noraini Ismail Apr 1988

A Study Of An Integral Equations For Computing Radial Distribution Functions, Noraini Ismail

Masters Theses

A two parameter integral equation, equation T is studied to compute radial distribution functions for a classical fluid whose single component particles interact pairwise according to a square-well potential function. A computer program originally written for a DEC 10 was modified to run on a DEC VAX. At the same time, modifications were made to take advantage of the faster VAX and to reduce the time an operator must spend to get a solution to the integral equation. Solutions were obtained for several densities, temperatures, and parameter values. Temperatures ranged from a high temperature gas to near critical temperatures. Accurate …

Go to article

Laser-Induced Collisional Detachment, D. Luo, John B. Delos, S. Geltman Apr 1988

Laser-Induced Collisional Detachment, D. Luo, John B. Delos, S. Geltman

Arts & Sciences Articles

A theoretical study is presented of the process of photodetachment of a negative ion by sub-threshold-frequency radiation in the presence of a simultaneous collision. Calculations are carried out for the H−-He case and the resulting cross section is compared with other competing processes, such as two-photon photodetachment and nonradiative collisional detachment.

Go to article

N-Level Quantum Systems With Gell-Mann Dynamic Symmetry, Foek T. Hioe Apr 1988

N-Level Quantum Systems With Gell-Mann Dynamic Symmetry, Foek T. Hioe

Physics Faculty/Staff Publications

A set of conditions is presented for an N-level quantum system to possess the Gell-Mann-type dynamic symmetry, which was introduced in an earlier paper. The characteristic set of constants of motion that the system has when it possesses the symmetry and also the equivalent two-level system, which the system can be reduced to, are also presented.

Go to article

Self Consistent Model Of The Glow Discharge, Hao Chen Apr 1988

Self Consistent Model Of The Glow Discharge, Hao Chen

Electrical & Computer Engineering Theses & Dissertations

The strong spatial variation of the electric field intensity in the vicinity of the cathode of a gas discharge requires the use of microscopic methods to describe the nonequilibrium behavior of the electron dynamics in this region. A one-dimensional Monte Carlo code was developed. It allows one to obtain the distribution of the electron drift velocity and rate coefficients for a given electric field intensity in the cathode fall. The results of this calculation are used to find the density distribution of charged particles in this region and consequently, by means of Poisson's equation, a corrected electric field intensity. In …

Go to article

A Calculation Of The Deuteron As A Biskyrmion, Alec Schramm, Yossef Dothan, L. Beidenharn Mar 1988

A Calculation Of The Deuteron As A Biskyrmion, Alec Schramm, Yossef Dothan, L. Beidenharn

Alec J Schramm

No abstract provided.

Go to article

Hyperspherical Description Of Two-Electron Systems, Anthony F. Starace Mar 1988

Hyperspherical Description Of Two-Electron Systems, Anthony F. Starace

Anthony F. Starace Publications

While the use of hyperspherical coordinates to describe two-electron systems is quite old, it was Macek's introduction of a quasi-separable approximation in hyperspherical coordinates which made possible a host of theoretical studies elucidating the symmetries of doubly-excited states and the dynamics of processes involving two-electron atoms and ions. This work, up to about mid-1982, has been reviewed by Fano. However, much additional progress has been made since 1982, particularly on the symmetries of doubly excited electronic states, on the correspondences with molecular descriptions of two-electron systems, on the limitations of the quasi-separable approximation at small and at large distances, and …

Go to article

The Calculation Of Photoionization Cross Sections, Anthony F. Starace Mar 1988

The Calculation Of Photoionization Cross Sections, Anthony F. Starace

Anthony F. Starace Publications

Photoionization is a sensitive probe of many-body and spin-dependent interactions. One can test our understanding of these interactions and the role they play in atomic dynamics by comparing the results of theoretical calculations with corresponding experimental measurements. One finds from such comparisons that our understanding of the photoionization process in atoms is excellent in many cases, imperfect in many others, and inadequate in still others. One finds in general also that the kinds of many-body and spin-dependent interactions included in a calculation is, in many cases, a more important consideration than the particular calculational method employed. In this brief report …

Go to article

Limitation Of The Semirelativistic Approach In Sum Rules And Related Calculations In Atomic Physics, M. L. Rustgi, P.T. Leung, S. A. Long Mar 1988

Limitation Of The Semirelativistic Approach In Sum Rules And Related Calculations In Atomic Physics, M. L. Rustgi, P.T. Leung, S. A. Long

Physics Faculty Publications and Presentations

It is shown that the semirelativistic approach, when applied consistently to atomic calculations involving the Thomas-Reiche-Kuhn sum rule or its applications, may lead to very inaccurate results.

Go to article

Static Magnetic Susceptibility Of Zn1-XMnXSe, J. K. Furdyna, N. Samarth, Richard B. Frankel, J. Spalek Mar 1988

Static Magnetic Susceptibility Of Zn1-XMnXSe, J. K. Furdyna, N. Samarth, Richard B. Frankel, J. Spalek

Physics

We present results of an investigation of the static magnetic susceptibility of Zn1-xMnxSe for x=0.05, 0.15, 0.30, and 0.45. From the Curie-Weiss behavior of the susceptibility at high temperatures, we determine the effective Mn-Mn exchange constant J1 to be -13.5±0.95 K. By using the results of our study in conjunction with direct measurements of the nearest-neighbor exchange integral JNN from inelastic neutron scattering by nearest-neighbor pairs, we obtain an estimate of the next-nearest-neighbor exchange constant J2=-2.4 K.

Go to article

Spectral Momentum Density From Graphite From Spectroscopy: Comparison With First Principles Calculations, Chao Gao, A. L. Ritter, John R. Dennison, N. A. Holzwarth Mar 1988

Spectral Momentum Density From Graphite From Spectroscopy: Comparison With First Principles Calculations, Chao Gao, A. L. Ritter, John R. Dennison, N. A. Holzwarth

All Physics Faculty Publications

We have measured the spectral momentum density ρ(E,q) of graphite by (e,2e) spectroscopy for momentum parallel and perpendicular to the crystal c axis. In the independent-electron approximation, ρ(E,q)=ΣG‖Uk(G)‖2 δ(q-k-G)δ(E-E(k)) where the one-electron wave function is Ψk(r)=eik⋅rΣGUk(G)eiG⋅r) and G is a reciprocal-lattice vector. The measurements covered a range of momentum parallel to the c axis equal to 0≤‖q‖≤1.84 Å-1 and a range of momentum perpendicular to the c axis equal to 0≤‖q‖≤2.35 Å-1. The energy range spanned the valence band of graphite from …

Go to article

The Role Of Dephasing In Some Recent Theories Of Quantum Localization, Paul Ernest Parris, Philip W. Phillips Mar 1988

The Role Of Dephasing In Some Recent Theories Of Quantum Localization, Paul Ernest Parris, Philip W. Phillips

Physics Faculty Research & Creative Works

We consider the transport of electrons or excitons through a random environment in the presence of constant site off-diagonal dephasing processes. It is shown that dephasing of this form will always defeat Anderson localization at long times. Some recent theories of quantum localization which depend upon such dephasing processes are, therefore, seen to be inconsistent.

Go to article

Granular Metal Films As Recording Media, Sy_Hwang Liou, C.L. Chien Feb 1988

Granular Metal Films As Recording Media, Sy_Hwang Liou, C.L. Chien

Sy-Hwang Liou Publications

High-density recording media require materials with a high magnetization and high coercivity as well as chemical stability, wear, and corrosion resistance. We explore the potential of granular metal films for recording media. Films of Fe granules about 150 Å in size embedded in an amorphous SiO2 matrix exhibit coercivities as high as 3 kOe at low temperatures and 1.1 kOe at room temperature, and magnetizations of about 150 emu/g. The methods with which these materials are fabricated, the essential microstructure characterization, and magnetic measurements are described.

Go to article

Review Of The Advancement Of Science, And Its Burdens By Gerald Holton, David W. Hafemeister Feb 1988

Review Of The Advancement Of Science, And Its Burdens By Gerald Holton, David W. Hafemeister

Physics

No abstract provided.

Go to article

Electronic Structure And Properties Of Sputtered Ta-Cu Films , K.D. Aylesworth, Sitaram Jaswal, M.A. Engelhardt, Z.R. Zhao, David J. Sellmyer Feb 1988

Electronic Structure And Properties Of Sputtered Ta-Cu Films , K.D. Aylesworth, Sitaram Jaswal, M.A. Engelhardt, Z.R. Zhao, David J. Sellmyer

David Sellmyer Publications

Films of TaxCu1-x have been produced in a co-sputtering system with dc- and rf-sputtering guns and a substrate attached to a rapidly rotating, water-cooled table. Samples were produced in the composition range 0.1≤x≤0.9. X-ray diffraction and electrical resistivity data between 4.2 and 300 K have been obtained. Diffraction measurements show that for 0.6≤x≤0.9 the samples are glassy. The room-temperature resistivities follow the Mooij correlation with a zero temperature coefficient of resistivity at a resistivity of 35 μΩ cm. The resistivity-versus-temperature data for Ta0.90Cu0.10 are compared to the extended Ziman-Faber theory …

Go to article

Driven 3-State Model And Its Analytic Solutions, C. E. Carroll, Foek T. Hioe Feb 1988

Driven 3-State Model And Its Analytic Solutions, C. E. Carroll, Foek T. Hioe

Physics Faculty/Staff Publications

For an atom or molecule in which two transitions are driven by laser beams, a three‐state model is used. Transitions among the three states are caused only by the oscillating electric fields of the laser beams. The amplitudes and detunings of the two laser beams, which are various functions of the time, appear in the Schrödinger equation for the atom or molecule. In certain cases, the Schrödinger equation can be solved analytically, to find transition probabilities and the probability of no transition. This is done by using Clausen’s special function, or by assuming that the sum of the two detunings …

Go to article

Effects Of Transport Coherence On The Mutual Annihilation Of Excitons, Demet Gulen, Vasudev M. Kenkre, Robert S. Knox, Paul Ernest Parris Feb 1988

Effects Of Transport Coherence On The Mutual Annihilation Of Excitons, Demet Gulen, Vasudev M. Kenkre, Robert S. Knox, Paul Ernest Parris

Physics Faculty Research & Creative Works

We report results of a theoretical investigation into the mutual annihilation of tight-binding excitons. The results are in apparent contradiction with intuitive expectations and provide corrections to expressions given by one of the present authors (V.M.K.) in an earlier analysis. A part of that analysis was based on a mapping of the dynamics of two mobile, mutually annihilating excitons onto the dynamics of a single exciton migrating in the presence of a fixed trap. We find that while this equivalence is valid for incoherent, randomly walking particles in an ordered system, it does not hold for an arbitrary degree of …

Go to article

Reply To Lung Cancer Risk From Rn In Chinese Study, Werner Hofmann, Robert Katz, Zhang Chunxiang Feb 1988

Reply To Lung Cancer Risk From Rn In Chinese Study, Werner Hofmann, Robert Katz, Zhang Chunxiang

Robert Katz Publications

We are writing in response to comments by V. A. Archer (Archer 1987) on our study of lung cancer incidence in two Chinese areas, designated as the high background and the control area (Hofmann et al. 1986). In his comments, he asserts that the epidemiological data suffer from two serious defects.

Go to article

Anomalous Layering Of Fe(C0) Adsorbed On Graphite, John R. Dennison, H. Taub, F. Y. Hansen, H. Shechter, R. Brener Feb 1988

Anomalous Layering Of Fe(C0) Adsorbed On Graphite, John R. Dennison, H. Taub, F. Y. Hansen, H. Shechter, R. Brener

All Physics Faculty Publications

Synchrotron x-ray diffraction experiments reveal the adsorption of iron pentacarbonyl [Fe(CO)5] on graphite basal-plane surfaces to be an extreme example of incomplete wetting in which only one solid layer of film coexists with bulk particles. Upon heating through the monolayer melting point, the amount of coexisting bulk solid first increases and then decreases. This anomalous layering behavior has not been observed in other systems exhibiting incomplete wetting, and we suggest that it is related to the steric properties of the Fe(CO)5 molecule.

Go to article

Semiclassical Interpretation Of Eigenvectors For Excited Atoms In External Fields, Robert Leonard Waterland, M. L. Du, John B. Delos Feb 1988

Semiclassical Interpretation Of Eigenvectors For Excited Atoms In External Fields, Robert Leonard Waterland, M. L. Du, John B. Delos

Arts & Sciences Articles

Eigenvectors for an electron in an atom in parallel electric and magnetic fields are calculated, and a semiclassical interpretation of their behavior is obtained. Eigenvectors can in this case be regarded as ‘‘wave functions in angular momentum space.’’ The matrix equation defining the eigenvectors is written as a difference equation, and then converted to a pseudodifferential equation; a systematic procedure is then used to construct a semiclassical approximation. It is found that the same classical Hamiltonian that has been previously used to calculate semiclassical eigenvalues provides a WKB-type representation of the eigenvectors. The development sheds new light on action-angle formulations …

Go to article

Versatile New Metalorganic Process For Preparing Superconducting Thin Films, M.E. Gross, M. Hong, Sy_Hwang Liou, P.K. Gallagher, J. Kwo Jan 1988

Versatile New Metalorganic Process For Preparing Superconducting Thin Films, M.E. Gross, M. Hong, Sy_Hwang Liou, P.K. Gallagher, J. Kwo

Sy-Hwang Liou Publications

A new technique for producing thin films of the high-temperature perovskite superconductors, LnBa2Cu3O7-x, where Ln represents a rare-earth element, using spin-on metalorganic precursors is described. Pyrolysis of the spin-coated films, consisting of mixed metal (2-ethyl hexanoates), leads to black films up to several microns thick whose degree of orientation is a function of the processing temperature and duration. Representative films of Y Ba2Cu3O7-x on MgO begin to exhibit orientation with the c axis perpendicular to the film plane at heat treatments above 900 °C. The superconducting behavior of a …

Go to article

First Prev Next Last