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Full-Text Articles in Physics

A Single-Solenoid Pulsed-Magnet System For Single-Crystal Scattering Studies, Zahirul Islam, Dana Capatina, Jacob P. C. Ruff, Ritesh K. Das, Emil Trakhtenberg, Hiroyuki Nojiri, Yasuo Narumi, Ulrich Welp, Paul C. Canfield Jan 2012

A Single-Solenoid Pulsed-Magnet System For Single-Crystal Scattering Studies, Zahirul Islam, Dana Capatina, Jacob P. C. Ruff, Ritesh K. Das, Emil Trakhtenberg, Hiroyuki Nojiri, Yasuo Narumi, Ulrich Welp, Paul C. Canfield

Ames Laboratory Publications

We present a pulsed-magnet system that enables x-raysingle-crystaldiffraction in addition to powder and spectroscopic studies with the magnetic field applied on or close to the scattering plane. The apparatus consists of a single large-bore solenoid, cooled by liquid nitrogen. A second independent closed-cycle cryostat is used for cooling samples near liquid helium temperatures. Pulsed magnetic fields close to ∼30 T with a zero-to-peak-field rise time of ∼2.9 ms are generated by discharging a 40 kJ capacitor bank into the magnet coil. The unique characteristic of this instrument is the preservation of maximum scattering angle (∼23.6°) on the entrance ...


Temperature And Magnetic-Field Dependence Of The Elastic Constants Of Ni-Mn-Al Magnetic Heusler Alloys, Xavier Moya, Lluís Mañosa, Antoni Planes, Thorsten Krenke, Mehmet Acet, Michel Morin, Jerel L. Zarestky, Thomas A. Lograsso Jul 2006

Temperature And Magnetic-Field Dependence Of The Elastic Constants Of Ni-Mn-Al Magnetic Heusler Alloys, Xavier Moya, Lluís Mañosa, Antoni Planes, Thorsten Krenke, Mehmet Acet, Michel Morin, Jerel L. Zarestky, Thomas A. Lograsso

Ames Laboratory Publications

We report on measurements of the adiabatic second-order elastic constants of the off-stoichiometric Ni54Mn23Al23 single-crystalline Heusler alloy. The variation in the temperature dependence of the elastic constants has been investigated across the magnetic transition and over a broad temperature range. Anomalies in the temperature behavior of the elastic constants have been found in the vicinity of the magnetic phase transition. Measurements under applied magnetic field, both isothermal and variable temperature, show that the value of the elastic constants depends on magnetic order, thus giving evidence for magnetoelastic coupling in this alloy system.


Optical And Magnetic Resonance Studies Of Novel Pristine And Photo-Oxidized Conjugated Polymers , Andrew Vernon Smith Jan 1994

Optical And Magnetic Resonance Studies Of Novel Pristine And Photo-Oxidized Conjugated Polymers , Andrew Vernon Smith

Retrospective Theses and Dissertations

Optical and magnetic resonance properties of several [pi]-conjugated polymers were studied and the results consolidated in this thesis. Photoluminescence (PL), electron spin resonance (ESR), and the novel Ultraviolet Optically Detected Magnetic Resonance (UV-ODMR) results on poly(p-phenyleneethynyleneaniline) (PPEA) derivatives are shown. The source wavelength, [lambda][subscript]ex, dependence of the ODMR is investigated on several [pi]-conjugated polymers including poly(p-phenylenevinylene) (PPV), poly(p-phenyleneacetylene) (PPA), and poly(3-alkylthiophene) (P3AT) derivative films. The effects of photo-oxidation on the UV- and laser-excited ODMR of dioctoxy substituted PPV (DOOPPV) films is shown. The ODMR results on unsubstituted PPV and CN-PPV films are ...


Theory Of Magneto-Optics And Circular Magnetic X-Ray Dichroism , Xindong Wang Jan 1994

Theory Of Magneto-Optics And Circular Magnetic X-Ray Dichroism , Xindong Wang

Retrospective Theses and Dissertations

This thesis contains three parts. In the first part, before getting into the discussion of magneto-optical properties for the systems under study, the author reviews some background subjects, such as the energy-band theory within the framework of density functional theory, the multiple scattering approach to the solution of band problem and its relation with the LMTO method, an account of the tight-binding LMTO method which we use exclusively in our calculations, the linear response theory and its application to the quantum theory of dielectric constants. In the second part, circular magnetic x-ray dichroism, as a powerful and newly developed experimental ...


Electronic And Magnetic Properties Of Strongly Correlated Systems , Tsan-Chuen Leung Jan 1991

Electronic And Magnetic Properties Of Strongly Correlated Systems , Tsan-Chuen Leung

Retrospective Theses and Dissertations

Self consistent, spin-polarized calculations are performed for Sc[subscript]2CuO[subscript]4, La[subscript]2CuO[subscript]4 with constrained d[superscript]9 configuration, and La[subscript]2NiO[subscript]4. For Sc[subscript]2CuO[subscript]4, both ferromagnetic and antiferromagnetic ground states are investigated and found to be unstable. Magnetic form factors are calculated and are discussed in view of experiments in La[subscript]2CuO[subscript]4. In the calculation for La[subscript]2CuO[subscript]4, the d[superscript]9 configuration is maintained by constraining the d[subscript]x[superscript]2-y[superscript]2 orbital to have exactly one hole. The Cu ...


Magnetic Relaxation, Flux Pinning And Critical Currents In Superconductors , Karl S. Lichtenberger Jan 1991

Magnetic Relaxation, Flux Pinning And Critical Currents In Superconductors , Karl S. Lichtenberger

Retrospective Theses and Dissertations

A systematic study of the magnetic flux pinning properties in superconductors has been undertaken in an attempt to understand the differences between the flux creep behavior of classical superconductors and high-temperature superconductors (HTSC's). In HTSC's, the ratio of the effective flux pinning energy to the thermal energy, U[subscript]0/kT, is much smaller than that of conventional superconductors, often approaching unity. This results in much larger creep rates in HTSC's than in conventional superconductors. It is necessary to find suitable models that describe flux creep in both classical superconductors (i.e., Nb-Ti) and HTSC's (i ...


Hydrogen Diffusion And Microstructure In Undoped And Boron-Doped Hydrogenated Amorphous Silicon: An Ir And Sims Study , Saibal Mitra Jan 1991

Hydrogen Diffusion And Microstructure In Undoped And Boron-Doped Hydrogenated Amorphous Silicon: An Ir And Sims Study , Saibal Mitra

Retrospective Theses and Dissertations

Hydrogenated amorphous silicon (a-Si:H) prepared by rf sputtering of a polycrystalline Si target at various rf powers 50 ≤ P ≤ 550 W (0.27-2.97 W/cm[superscript]2), target to substrate distance 1 ≤ d ≤ 2[superscript]'', and varying hydrogen partial pressures. Doping was accomplished by introducing diborane (B[subscript]2H[subscript]6) in the plasma. Hydrogen diffusion was studied from the depth profiles obtained from the SIMS on multilayered a-Si:H/a-Si:(H,D)/a-Si:H samples;The properties of the samples were characterized by IR absorption, optical gap measurements and ESR. IR yielded quantitative and qualitative information total ...


Propagation Of Electromagnetic Radiation In Some Linear And Nonlinear Dielectric Stacks , Steven R. Stuve Jan 1991

Propagation Of Electromagnetic Radiation In Some Linear And Nonlinear Dielectric Stacks , Steven R. Stuve

Retrospective Theses and Dissertations

In this dissertation, we study the propagation of electromagnetic radiation in dielectric stacks, a class of structures made up of layers of dielectric which we assume to be lossless and nondispersive. We consider stacks composed of linear dielectrics with and without a nonlinearity. For computational simplicity, we often consider two specific types of dielectric stacks which we refer to as alternating and impurity stacks. Successive layers in an alternating stack alternate between two different types of dielectrics. The impurity stack is defined to be an alternating stack with one layer modified to create an "impurity" layer;We first study the ...


High-Resolution Angle-Resolved Photoemission Studies Of High Tc Superconductor Bi2sr2cacu2o8 , Rong Liu Jan 1990

High-Resolution Angle-Resolved Photoemission Studies Of High Tc Superconductor Bi2sr2cacu2o8 , Rong Liu

Retrospective Theses and Dissertations

An angle-resolved photoemission study of the normal and superconducting states in Bi[subscript]2Sr[subscript]2CaCu[subscript]2O[subscript]8 was performed. Measurements in the normal state show bands dispersing through the Fermi level from at least 350 meV below E[subscript]F. The Fermi level crossings are consistent with local-density band calculation, including a point calculated to be of Bi-O character. Additional measurements were made where bands crossed the Fermi level between 100 and 250K, along with measurements on an adjacent Pt foil. The Fermi edges of both materials agree to within the noise. Below the Fermi level, the ...


Scanning Tunnel Microscopy Studies Of Tetrahedrally Bonded Materials , Patricia E. Allen Jan 1990

Scanning Tunnel Microscopy Studies Of Tetrahedrally Bonded Materials , Patricia E. Allen

Retrospective Theses and Dissertations

The Scanning Tunnel Microscope (STM) is a surface analysis tool that has been used to study the geometric and electronic properties of metals, semimetals and semiconductors. Evaporated gold deposited on glass was examined as a preliminary test of the McAllister/RHK STM. Calibration of the STM system was accomplished by imaging annealed pyrolytic graphite (APG), but with surprising results. The peak spacing agreed with the accepted value for STM graphite images of 2.46 A, but the shape of the peaks were often distorted. These distortions can be understood in view of the theoretical work of Kobayashi and Tsukada on ...


Optical Properties And Electronic Structures Of D- And F-Electron Metals And Alloys, Ag-In, Ni-Cu, Auga2, Ptga2, [Beta]'-Nial, [Beta]'-Coal, Cesn3, And Lasn3 , Kwang Joo Kim Jan 1990

Optical Properties And Electronic Structures Of D- And F-Electron Metals And Alloys, Ag-In, Ni-Cu, Auga2, Ptga2, [Beta]'-Nial, [Beta]'-Coal, Cesn3, And Lasn3 , Kwang Joo Kim

Retrospective Theses and Dissertations

Optical properties and electronic structures of disordered Ag[subscript]1-xIn[subscript]x (x = 0.0, 0.04, 0.08, 0.12) and Ni[subscript]1-xCu[subscript]x(x = 0.0, 0.1, 0.3, 0.4) alloys and ordered AuGa[subscript]2, PtGa[subscript]2, [beta][superscript]'-NiAl, [beta][superscript]'-CoAl, CeSn[subscript]3, and LaSn[subscript]3 have been studied. The complex dielectric functions have been determined for Ag[subscript]1-xIn[subscript]x,Ni[subscript]1-xCu[subscript]x,AuGa[subscript]2, and PtGa[subscript]2 in the 1.2-5.5 eV region and for CeSn[subscript]3 and LaSn ...


Magnetic And Thermal Properties Of High Tc Superconductors , Wonchoon Lee Jan 1990

Magnetic And Thermal Properties Of High Tc Superconductors , Wonchoon Lee

Retrospective Theses and Dissertations

Measurements of the normal state magnetic susceptibility [chi](T) of YBa2Cu3O7, Bi1.8Pb0.2Sr2CaCu2O8+[delta], and Bi2- xPb xSr2Ca2Cu3O10+[delta] (x = 0.2 and 0.25) were carried out. All [chi](T) data show negative curvature below ~ 2T c. The data for YBa2Cu3O7 are in excellent agreement with a new calculation of the superconducting fluctuation and diamagnetism. From the analysis, we infer s-wave pairing and microscopic parameters are obtained. For [chi](T) of YBa2Cu3O7, part of the negative curvature is inferred to arise from the normal state background. We find a strong temperature dependent anisotropy [delta][chi] ≡ [chi] c - [chi ...


High Resolution Electron Energy Loss Studies Of O2, H, N, No, And N2o Adsorption On Germanium Surfaces , Anthony G. Entringer Jan 1990

High Resolution Electron Energy Loss Studies Of O2, H, N, No, And N2o Adsorption On Germanium Surfaces , Anthony G. Entringer

Retrospective Theses and Dissertations

The first high resolution electron energy loss spectroscopy (HREELS) studies of the oxidation and nitridation of germanium surfaces are reported. Both single crystal Ge(111) and disordered surfaces were studied. Surfaces were exposed to H, O[subscript]2, NO, N[subscript]2O, and N, after cleaning in ultra-high vacuum. The Ge surfaces were found to be non-reactive to molecular hydrogen (H[subscript]2) at room temperature. Exposure to atomic hydrogen (H) resulted hydrogen adsorption as demonstrated by the presence of Ge-H vibrational modes. The HREEL spectrum of the native oxide of Ge characteristic of [nu]-GeO[subscript]2 was obtained ...


Photoemission And Inverse Photoemission Studies Of Cesn3 And Lasn3 , Sayong Hong Jan 1990

Photoemission And Inverse Photoemission Studies Of Cesn3 And Lasn3 , Sayong Hong

Retrospective Theses and Dissertations

Angle-resolved photoemission spectra (ARPES) and angle-resolved inverse photoemission spectra from single crystals of CeSn[subscript]3 (111) and LaSn[subscript]3 (111) were measured and discussed. The results were compared with the calculated band structures and fitted by the Gunnarsson-Schonhammer (G-S) model. The two-peak structure from the resonance photoemission of CeSn[subscript]3 was fitted by G-S model well by placing the single f-level at 2.0 eV below the Fermi energy before hybridization. ARPES from both CeSn[subscript]3 and LaSn[subscript]3 showed a peak near the Fermi energy without noticeable dispersion. In LaSn[subscript]3, the experimental ...


Localization And Electron-Phonon Interaction In Disordered Systems , Yi Wan Jan 1990

Localization And Electron-Phonon Interaction In Disordered Systems , Yi Wan

Retrospective Theses and Dissertations

The problem of localization of electrons in the presence of electron-phonon interaction in disordered one-dimensional system is studied. In the mean-field approximation, the electron-phonon interaction results in a distorted lattice, the Peierls instability. At the same time, a gap opens at the Fermi level in the electron band. It is known that the scattering of the electrons by the disorder will destroy the lattice distortion and close the gap. However, there is disagreement on the way this happens and on the nature of the resulting electronic states. Recent progress in the experimental and theoretical studies of the one-dimensional organic polymer ...


Inverse-Photoemission Spectroscopy Of Fexo, Ag , Bongsoo Kim Jan 1990

Inverse-Photoemission Spectroscopy Of Fexo, Ag , Bongsoo Kim

Retrospective Theses and Dissertations

I measured the inverse-photoemission spectra (IPES) of iron oxides grown on an Fe substrate, and calculated the band structure of paramagnetic FeO to analyze the IPES. The band calculation showed some overlap between Fe3 d states and O2 p states in the region of occupied states, and s,p-like states of Fe in the unoccupied region. Isochromatic IPES showed structures at ~2.5 eV and ~7.5 eV above the Fermi energy. I estimate the full band gap of FeO as 2.5 eV from the IPES data;Angle-resolved inverse-photoemission spectra (ARIPES) have been measured on single-crystal Ag. The results ...


Synchrotron Radiation Photoemission Study Of Metal Overlayers On Hydrogenated Amorphous Silicon At Room Temperature , Tun-Wen Pi Jan 1990

Synchrotron Radiation Photoemission Study Of Metal Overlayers On Hydrogenated Amorphous Silicon At Room Temperature , Tun-Wen Pi

Retrospective Theses and Dissertations

We study Au, Cr, and Ag metals evaporated on rf-sputtered a-Si:H at room temperature using high-resolution photoemission techniques. For Au/a-Si:H, three regions of coverage can be classified: an unreacted region with an equivalent thickness of 2 A, followed by an intermixed Au/a-Si overlayer (~9 A), and a dual-phase region at higher coverage. Au adatoms are dispersely distributed in the unreacted region. They subsequently cluster in the intermixed region, where they attach to Si atoms that are not hydrogen-bonded, suggesting that the intermixed Si were mainly those that had dangling bonds. In the dual-phase region, two sets ...


Electron Beam Decompositions Of Ionic Crystals , Qun Dou Jan 1989

Electron Beam Decompositions Of Ionic Crystals , Qun Dou

Retrospective Theses and Dissertations

Electron beam induced decompositions of alkali halides were studied. Compositional and topological changes induced by low-energy electron irradiation have been observed on thin films and single crystals of alkali-halides using scanning electron microscopy (SEM) and Auger electron microscopy (SAM). Alkali-metal rich structures with diameters of up to several microns were found on the sample surfaces;The temperature dependence of desorption yields were measured using a mass-spectrometer. We observed two temperature regions, each features a different activation Oil, Gas, and Energy;Temperature dependence of electron induced decomposition of CaF2 was studied using Auger spectroscopy and Energy dispersive x-ray (EDX) analysis. We ...


Flux Quantization Effects In Disordered Normal Metal Rings And Superconducting Networks , Qiming Li Jan 1989

Flux Quantization Effects In Disordered Normal Metal Rings And Superconducting Networks , Qiming Li

Retrospective Theses and Dissertations

The effects of the magnetic flux on the properties of disordered normal metal rings and bond or site diluted two-dimensional superconducting networks are investigated theoretically, with an emphasis on the quantum coherence of the electrons and the localization nature in the disordered systems. The conductance of disordered metal rings in magnetic field is obtained via the Landauer's formula through calculations of the localization length L[subscript] c. The important role of the ensemble averaging and the self-averaging to obtain the half-flux-quantum h/2e conductance oscillation is demonstrated unambiguously in both rings of a strictly one-dimensional geometry and rings with ...


Searching For Heavy Fermion Materials In Ce Intermetallic Compounds , Jinke Tang Jan 1989

Searching For Heavy Fermion Materials In Ce Intermetallic Compounds , Jinke Tang

Retrospective Theses and Dissertations

The low temperature heat capacity, magnetic susceptibility and electrical resistivity were studied for a series of Ce intermetallic compounds. No heavy fermion behavior was found in these compounds. CePtGa[subscript]3 has a rounded peak at ~1.7K in its heat capacity, which is shifted to higher temperatures in magnetic fields (~6K at 9.8T). The origin of this peak is believed to be due to a spin glass type transition. CeCd[subscript]11 has an unusual temperature dependence of its heat capacity which is due to a crystalline electric field (CEF) effect which occurs at an exceptionally low temperature ...


A Photoemission Study Of Samarium On Silicon , An-Ban Yang Jan 1989

A Photoemission Study Of Samarium On Silicon , An-Ban Yang

Retrospective Theses and Dissertations

A photoemission study was performed on the chemisorption of samarium on three different kinds of silicon substrates, i.e., crystal Si(111), amorphous Si (a-Si), and hydrogenated amorphous Si (a-Si:H), to understand completely the chemical and physical phenomena underlying the interface formation. The core-level spectra clearly indicate the existence of three interface-formation regimes. Two chemically reacted shifts are observed and identified as disilicide phase and solid solution, respectively, and a critical coverage corresponding to the onset of strong chemical reaction is also shown. Moreover, the Si atoms show no sign of surface-segregation behavior, and a heterogeneous interface is indicated ...


Preparation And Characterization Of Hydrogenated Amorphous Germanium And Hydrogenated Amorphous Germanium Carbide Thin Films , Hai-Sheng Wu Jan 1988

Preparation And Characterization Of Hydrogenated Amorphous Germanium And Hydrogenated Amorphous Germanium Carbide Thin Films , Hai-Sheng Wu

Retrospective Theses and Dissertations

Hydrogenated amorphous germanium (a-Ge:H) and germanium carbide (a-Ge[subscript] 1-xC[subscript] x:H) films were prepared by rf sputtering of a polycrystalline Ge target in a vacuum ~4 x 10[superscript]-7 Torr at various rf power 50 ≤ P ≤ 600 W (0.27-3.3 W/cm[superscript]2), target-substrate distance 1 ≤ d ≤ 7[superscript]'', varying partial pressures of Ar, H[subscript]2, and C[subscript]3H[subscript]8, and flow rates f. The vibrational and opto-electronic properties such as infrared (IR) absorption, optical gap, electron-spin-resonance (ESR) signals, and conductivities vary with deposition conditions. The photoconductivity [sigma][subscript] ph, in ...


X-Ray Diffraction Characterization Of The Quality And Thermal Stability Of Ii-Vi Semiconductor Superlattices , Ralph David Knox Jan 1988

X-Ray Diffraction Characterization Of The Quality And Thermal Stability Of Ii-Vi Semiconductor Superlattices , Ralph David Knox

Retrospective Theses and Dissertations

The quality and thermal stability of (1,1,1) oriented HgTe-CdTe, Hg[subscript]1 - xMn[subscript] xTe-CdTe, Hg[subscript]1 - xZn[subscript] xTe-CdTe, and Hg[subscript]1 - xCd[subscript] xTe-CdTe superlattices (SLs) and (0,0,1) oriented CdTe-ZnTe SLs, grown by molecular beam epitaxy, are investigated using x-ray diffraction. Two significant research contributions are achieved in this investigation. First, SL interdiffusion is investigated using an in-situ x-ray diffraction method, which represents a fundamentally different approach compared to the quenched sample method. Second, the step model structure factor, which includes angle dependent atomic scattering factors, atom vacancies, and interface transition regions ...


Nuclear Magnetic Resonance Study Of The Metal-Nonmetal Transition In Lanthanum Hydrides , Chii-Tzong Chang Jan 1988

Nuclear Magnetic Resonance Study Of The Metal-Nonmetal Transition In Lanthanum Hydrides , Chii-Tzong Chang

Retrospective Theses and Dissertations

Proton spin-lattice relaxation time (T[subscript]1) measurements have been used to investigate the metal-nonmetal (MNM) transition in the lanthanum hydride system, LaH[subscript] x (2 ≤ x ≤ 3), on samples prepared from highest purity Ames Laboratory lanthanum and also from the same lanthanum doped with controlled low levels of gadolinium. The dependence of hydrogen diffusion parameters on hydrogen concentration x was also determined;The temperature and composition dependence of the MNM transition in this system affects the proton T[subscript]1 through the electronic density-of-states at the Fermi level, N(E[subscript] F). In the pure samples, T[subscript]1 ...


Nuclear Magnetic Resonance Study Of Hydrogen In Niobium-Vanadium Alloys , Lyle Raymond Lichty Jan 1988

Nuclear Magnetic Resonance Study Of Hydrogen In Niobium-Vanadium Alloys , Lyle Raymond Lichty

Retrospective Theses and Dissertations

Proton spin relaxation rates have been measured across the random alloy system Nb[subscript] yV[subscript] 1 - yH[subscript] x at temperatures from 10 to 800 K and various frequencies from 4.45 to 127.5 MHz. Enhanced spin-lattice relaxation rates found below 100 K in all samples with Nb, including NbH[subscript]0.2, at frequencies of 40 MHz and below have been explained by a process of dipolar cross relaxation between proton Zeeman energy levels and the combined Zeeman-quadrupole levels of [superscript]93Nb. A semi-quantitative model, applicable in metal-hydrogen as well as other multi-spin systems, has been developed ...


Spin Polarization Effects In The Photoluminescence Of Polythiophene , Bret Clark Hess Jan 1988

Spin Polarization Effects In The Photoluminescence Of Polythiophene , Bret Clark Hess

Retrospective Theses and Dissertations

Photoluminescence (PL), optically detected magnetic resonance (ODMR), and nonresonant magnetic field effects (NFE) have been studied in polythiophene (PT) and poly(3-alkylthiophene) (P3AT). The PT samples studied were chemically coupled PT (c-PT) and electrochemically coupled PT (e-PT); the P3AT samples were poly(3-hexylthiophene) (HPT) and a copolymer of 3-benzylthiophene and 3-hexylthiophene (BHPT);The PL spectra of PT and P3AT exhibit a broad band centered between 1.6-1.9 eV, a narrow peak at 1.8-1.95 eV, and 0.18 eV phonon replicas of the narrow peak. The PL spectrum of e-PT is similar to the published spectra, while the ...


Average Dielectric Function And Spectral Representation Of Composites With Fractal Structure , Kunal Prasad Ghosh Jan 1988

Average Dielectric Function And Spectral Representation Of Composites With Fractal Structure , Kunal Prasad Ghosh

Retrospective Theses and Dissertations

The thesis is organized in three parts, each of them in the form of an independent paper. In Part I, titled "A Spectral Theory for Two-Component Porous Media", the spectral representation formalism is applied to successfully explain the observed static (frequency-independent) and dynamic (frequency-dependent) dielectric properties of rock-and-brine systems. In addition, the theory shows scaling properties which were formulated earlier for discrete systems, namely, random resistor networks. A new critical behavior in these porous systems is discovered, whose critical exponent can be related to the transport critical exponents. The exponents describing power law properties of the average dielectric function do ...


Nuclear Magnetic Resonance Studies Of Metal-Hydrogen Systems , Jinwoo Han Jan 1988

Nuclear Magnetic Resonance Studies Of Metal-Hydrogen Systems , Jinwoo Han

Retrospective Theses and Dissertations

Pulsed nuclear magnetic resonance methods have been used to investigate the properties of various metal-hydrogen systems including ZrH[subscript] x, ScH[subscript] x, NbH[subscript] x, VH[subscript] x etc. For pure dihydride-phase samples of ZrH[subscript] x, the spin-lattice relaxation time T[subscript]1 has been measured as a function of temperature in the temperature range from 10 K to 1300 K at 12.2 MHz and 40 MHz. These measurements show that the activation energy E[subscript] a for hydrogen diffusion first increases smoothly from 0.57 eV/atom at x = 1.58 to 0.63 eV/atom ...


Superconductivity, Magnetism, And Charge Density Wave Formation In Ternary Compounds With The Sc5co4si10-Type Structure , Hung-Duen Yang Jan 1987

Superconductivity, Magnetism, And Charge Density Wave Formation In Ternary Compounds With The Sc5co4si10-Type Structure , Hung-Duen Yang

Retrospective Theses and Dissertations

The variation of the superconducting transition temperature T(,c) with hydrostatic pressure up to 23.7 kbar is reported for eleven compounds with the Sc(,5)Co(,4)Si(,10)-type structure. Most of these compounds display a modest linear depression of T(,c) with pressure (dT(,c)/dp (TURN) 10('-5) K/bar), however, two materials, Lu(,5)Ir(,4)Si(,10) and Lu(,5)Rh(,4)Si(,10), undergo a discontinuous transformation above a critical pressure of about 20 kbar to a state with a significantly higher T(,c);The resistivity and magnetic susceptibility show an anomaly in ...


A Study Of Deposition Conditions And Hydrogen Motion In Rf Sputtered Hydrogenated Amorphous Silicon , Mark L. Albers Jan 1987

A Study Of Deposition Conditions And Hydrogen Motion In Rf Sputtered Hydrogenated Amorphous Silicon , Mark L. Albers

Retrospective Theses and Dissertations

Three series of a-Si:H films were prepared by r.f. sputtering in He/H(,2), Ar/H(,2), and Xe/H(,2) atmospheres. The r.f. power used for deposition was varied from 0.27 W/cm('2) to 3.3 W/cm('2) for each of these three series. The films were characterized using mechanical thickness, optical transmission, infrared, and electron spin resonance measurements;The deposition rates of these films were found to vary linearly with deposition rates predicted from known sputtering yields. The total hydrogen concentration of the films as a function of deposition rate was found ...