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Articles 18061 - 18090 of 20343
Full-Text Articles in Physics
Selective Decay And Coherent Vortices In Two-Dimensional Incompressible Turbulence, William H. Matthaeus, W. Troy Stribling, Daniel Martinez, Sean Oughton, David Montgomery
Selective Decay And Coherent Vortices In Two-Dimensional Incompressible Turbulence, William H. Matthaeus, W. Troy Stribling, Daniel Martinez, Sean Oughton, David Montgomery
Dartmouth Scholarship
Numerical solution of two-dimensional incompressible hydrodynamics shows that states of a near-minimal ratio of enstrophy to energy can be attained in times short compared with the flow decay time, confirming the simplest turbulent selective decay conjecture, and suggesting that coherent vortex structures do not terminate nonlinear processes. After all possible vortex mergers occur, the vorticity attains a particlelike character, suggested by the late-time similarity of the streamlines to Ewald potential contours.
Anisotropic, Time-Dependent Solutions In Maximally Gauss-Bonnet Extended Gravity, T. Kitaura, James Thomas Wheeler
Anisotropic, Time-Dependent Solutions In Maximally Gauss-Bonnet Extended Gravity, T. Kitaura, James Thomas Wheeler
All Physics Faculty Publications
In an arbitrary number of dimensions, we find the full exact anisotropic, time-dependent, diagonal-metric solutions to maximally Gauss-Bonnet extended gravity theory. This class of theories, for which the lagrangian is an arbitrary linear combination of dimensionally extended Euler forms, is the most general gravitational theory in which the field equations contain no more than second derivatives of the metric.
We show that the space-time exponentially approaches an asymptotic state of constant, anisotropic curvature and prove three theorems concerning two generic types of singularities. The first theorem gives conditions for the existence of Kasner-like curvature singularities. For these the metric diverges …
Recoil Ions From Near-Zero-Impact-Parameter H+-Xe Collisions In The Range 20- 70 Kev, Wen-Qin Cheng, M. Eugene Rudd
Recoil Ions From Near-Zero-Impact-Parameter H+-Xe Collisions In The Range 20- 70 Kev, Wen-Qin Cheng, M. Eugene Rudd
M. Eugene Rudd Publications
Recoil ions from very small impact-parameter collisions of 20-70-keV protons with xenon atoms were selected by viewing only those ejected at 50° and 70° from the beam direction. These ions were charge-state analyzed and the cross sections determined for the production of charge states up to 6+. In such collisions, multiple ionization accounts for 60-80% of the ionizing collisions and 80-90 % of the total ionization.
Rbe Vs. Dose For Low Doses Of High-Let Radiations, Robert Katz, F. A. Cucinotta
Rbe Vs. Dose For Low Doses Of High-Let Radiations, Robert Katz, F. A. Cucinotta
Robert Katz Publications
(LET) radiations varies with cellular radiosensitivity parameters and the radiation environment. Of special interest is that the RBE varies as the dose of high-LET radiation to the power (1/m - 1) where /m is the “target number” parameter, which varies from 2-4 in different cell lines. This applies to neutrons as well as to heavy ions at sufficiently low doses such that cells are not activated in the γ-kill mode; that is, the tracks of single heavy ions are sufficiently far apart so that there are few cases of inter-track inactivation.
Comment On “Microdosimetry And Katz’S Track Structure Theory” By Marco Zaider, Robert Katz
Comment On “Microdosimetry And Katz’S Track Structure Theory” By Marco Zaider, Robert Katz
Robert Katz Publications
To test radiobiological models one needs data from X- or γ-ray and HZE track segment irradiations of the widest possible dynamic range in dose, LET, end points, and test objects (enzymes, viruses, bacteria, cells, tissues, organs, and organisms). Some data are currently available. There are excellent data on the inactivation of dry enzymes and viruses which should serve as a test of every biophysical model. On many occasions Zaider has asserted the superiority of microdosimetric over track structure models, asserting that “radial dose distributions (on which track structure theory is based) are generally poor substitutes for exact microdosimetric distributions.” I …
Kähler-Chern-Simons Theory And Symmetries Of Anti-Self-Dual Gauge Fields, V. Parameswaran Nair, Jeremy Schiff
Kähler-Chern-Simons Theory And Symmetries Of Anti-Self-Dual Gauge Fields, V. Parameswaran Nair, Jeremy Schiff
Publications and Research
Kähler-Chern-Simons theory, which was proposed as a generalization of ordinary Chern-Simons theory, is explored in more detail. The theory describes anti-self-dual in-stantons on a four-dimensional Kähler manifold. The phase space is the space of gauge potentials, whose symplectic reduction by the constraints of anti-self-duality leads to the moduli space of instantons. We show that infinitesimal Bäcklund transformations, previously related to "hidden symmetries" of instantons, are canonical transformations generated by the anti-self-duality constraints. The quantum wave functions naturally lead to a generalized Wess-Zumino-Witten action, which in turn has associated chiral current algebras. The dimensional reduction of the anti-self-duality equations leading to …
Population Of Highly Excited Intermediate Resonance States By Electron Transfer And Excitation, Reinhold S. Schuch, Edson L B Justiniano, Michael Schulz, Sheldon Datz, Peter F. Dittner, J. P. Giese, Herbert F. Krause, Harald Schone, Charles Randy Vane, Stephen M. Shafroth
Population Of Highly Excited Intermediate Resonance States By Electron Transfer And Excitation, Reinhold S. Schuch, Edson L B Justiniano, Michael Schulz, Sheldon Datz, Peter F. Dittner, J. P. Giese, Herbert F. Krause, Harald Schone, Charles Randy Vane, Stephen M. Shafroth
Physics Faculty Research & Creative Works
Coincidences between two sulfur K x rays were detected from collisions of hydrogenlike S ions with H2 gas in the projectile energy range between 150 and 225 MeV. These K x rays are emitted in the decay of doubly excited states formed in the collisions via transfer and excitation. The excitation function for two coincident Kβ transitions peaks at about 175 MeV, slightly above the expected KMM resonance energy for resonant transfer and excitation (RTE). This demonstrates the occurrence of ΔN≥2 transitions (i.e., KMM and higher resonances) in the RTE process. The cross sections for the population of the …
Probing The Metal-Nonmetal Transition In Thin Metal Overlayers Using Resonant Photoemission, Peter A. Dowben, D. Lagraffe, Dongqi Li, G. Vidali, L. Zhang, L. Dottl, M. Onellion
Probing The Metal-Nonmetal Transition In Thin Metal Overlayers Using Resonant Photoemission, Peter A. Dowben, D. Lagraffe, Dongqi Li, G. Vidali, L. Zhang, L. Dottl, M. Onellion
Peter Dowben Publications
We have studied one and two monolayers of barium on Ni(111) and of mercury on Cu(100). Using resonant photoemission, we have found core excited electrons become delocalized with increasing barium coverage. Similarly, upon formation of the mercury bilayer (as determined by low-energy electron diffraction and by atom-beam scattering), there is a substantial increase in the screening of the photohole. A transition of the electronic structure akin to a metal-nonmetal (metal-insulator) transition is apparent in these final-state effects. The band structure for Hg is similar to the band structure expected for a free-standing film with a free-electron sd band. The delocalization …
Novel Methods For Deposition Of Boron Carbide Films, J. Mazurowski, S. Baral-Tosh, G. Ramseyer, J.T. Spencer, Yoon-Gi Kim, Peter A. Dowben
Novel Methods For Deposition Of Boron Carbide Films, J. Mazurowski, S. Baral-Tosh, G. Ramseyer, J.T. Spencer, Yoon-Gi Kim, Peter A. Dowben
Peter Dowben Publications
By combining pentaborane (B5H9) and decarborane (B10H14) with methane in a plasma reactor, a variety of boron-carbides can be made over a wide range of compositions. The resulting thin films have uniform composition and appear to be polycrystalline.
The Deposition Of Nickel Boride Thin Films By Borane And Metallaborane Cluster Compounds, John A. Glass Jr., Shreyas Kher, Yoon-Gi Kim, Peter A. Dowben, James T. Spencer
The Deposition Of Nickel Boride Thin Films By Borane And Metallaborane Cluster Compounds, John A. Glass Jr., Shreyas Kher, Yoon-Gi Kim, Peter A. Dowben, James T. Spencer
Peter Dowben Publications
The deposition of high purity and controlled stoichiometry metal boride thin-film materials has recently received considerable interest. Borane clusters and their corresponding metal complexes are currently Wig investigated in our laboratories for their utility as unique source materials for the formation of metallic boride thin films by MOCVD. Variable composition nickel boride thin films ranging from 0.1 micron to several microns have been prepared. These new materials have been characterized by SEM, AES and XES. The magnetic properties of these new films have been investigated with torque magnetometry and magneto-optic Kerr effect magnetometry.
Thermal Desorption Of Hg Monolayers From Cu(100), Y.J. Kime, Jiandi Zhang, Peter A. Dowben
Thermal Desorption Of Hg Monolayers From Cu(100), Y.J. Kime, Jiandi Zhang, Peter A. Dowben
Peter Dowben Publications
A two dimensional phase transition from one adlayer structure to another is an inherent part of the thermal desorption of one monolayer of Hg on Cu(100). The energetics of this phase transition have been studied using thermal desorption spectroscopy (TDS). The TDS spectra reflect the coexistence of the two structural phases for a range of Hg exposures. The TDS spectra have been analyzed within a Polanyi-Wigner framework modified to account for the phase transition.
Double Excitation Of Helium By Fast Particles Of Charge Z, James H. Mcguire, Jack C. Straton
Double Excitation Of Helium By Fast Particles Of Charge Z, James H. Mcguire, Jack C. Straton
Physics Faculty Publications and Presentations
Results of calculations of double excitation of helium to n=2 states for fast projectiles of charge Z are presented. Nonzero Z3 contributions for single and double excitation occur only when time-ordering contributions from the second-order amplitude are nonzero. For double excitation, electron correlation must also be nonzero to obtain Z3 terms. The time-ordering effects arise from virtual off-energy-shell intermediate states. As with second-order amplitudes for Thomas singularities in electron capture, the energy-nonconserving amplitude is connected to the second-order energy-conserving amplitude by a dispersion relation. Comparison is made with experiment.
Effect Of Microstructure On Coercivity Of C-Axis In-Plane-Oriented Co/Cr Multilayered Films, D. Wang, David J. Sellmyer, George C. Hadjipanayis
Effect Of Microstructure On Coercivity Of C-Axis In-Plane-Oriented Co/Cr Multilayered Films, D. Wang, David J. Sellmyer, George C. Hadjipanayis
David Sellmyer Publications
The effect of the insertion of nonmagnetic Cr planes on coercivities of thin Co films has been studied in Co/Cr multilayered films. The in-plane coercivity Hc║ can be as high as 1800 Oe and can be adjusted easily, ranging from 650 to 1800 Oe. The large Hc║ is related to the Co(110) in-plane orientation which is induced by a Cr(100) in-plane-oriented underlayer. In addition, it appears that a decreasing saturation magnetization Ms, a decreasing average structural coherence length D in the direction perpendicular to the film, and a narrowing distribution of D are correlated …
Magneto-Optic And Optical Characterization Of Tb/Co Compositionally Modulated Amorphous Films, Liang-Yao Chen, Ping He, S. Nafis, William A. Mcgahan, John A. Woollam, David J. Sellmyer
Magneto-Optic And Optical Characterization Of Tb/Co Compositionally Modulated Amorphous Films, Liang-Yao Chen, Ping He, S. Nafis, William A. Mcgahan, John A. Woollam, David J. Sellmyer
David Sellmyer Publications
Amorphous Tb/Co compositionally modulated films were deposited on Si substrates with different modulation layer thicknesses ranging from about 2.5 to 15 Å. The nominal Tb to Co layer thickness ratios were systematically varied and the complex refractive index (n and k) and polar magneto-optical Kerr effects (rotation and ellipticity) were measured in the 3000–8000-Å spectral range as well. The samples were divided into two groups. In one group, the thickness of the Co layers was fixed, the Tb layer thickness varied. In the second group, the thickness of the Tb layer was fixed, and that of the Co …
Magneto-Optical Properties Of Mnbial Thin Films, J. X. Shen, Roger D. Kirby, David J. Sellmyer, Y. J. Wang
Magneto-Optical Properties Of Mnbial Thin Films, J. X. Shen, Roger D. Kirby, David J. Sellmyer, Y. J. Wang
Roger Kirby Publications
Mn-Bi-Al thin films. were produced by sequential evaporation of the constituents, followed by an anneal at 300 °C. The temperature and composition dependencies of the Kerr rotation angle, absolute reflectivity, and magnetic anisotropy were measured. The results show that, up to 30 at. % Al concentration, the thin films retain the pure MnBi hexagonal structure. Further, for suitable Al content, the films have the same large Kerr rotation as MnBi. Pure MnBi films exhibit perpendicular anisotropy at room temperature and in-plane anisotropy for temperatures below 142 K. In contrast,. the Al-doped films prepared here have perpendicular anisotropy down to at …
Transport Properties Of An Interacting Lattice Gas Model In A Charge Density Gradient By Monte Carlo Simulation, Ras B. Pandey, Songping Gao
Transport Properties Of An Interacting Lattice Gas Model In A Charge Density Gradient By Monte Carlo Simulation, Ras B. Pandey, Songping Gao
Faculty Publications
A two-dimensional lattice is considered with a linear charge-density gradient produced by a charge source at one end and a sink at the opposite end. A fraction p of the lattice sites are occupied by mobile particles that interact only with neighboring particles and empty sites (the substrate) and carry charges from source to sink; the charge neutrality of the whole lattice is maintained. The root-mean-square (rms) displacement of the particles (i.e., the tracers) and their effective conductivity for the charge transport are studied as a function of temperature and concentration p. The rms displacement shows a crossover from diffusion …
The Process-Controlled Magnetic Properties In Nanostructured Fe/Ag Composite Films, Y.Z. Zhang, Sy_Hwang Liou, R.J. Deangelis, K.W. Lee, C.P. Reed, A. Nazareth
The Process-Controlled Magnetic Properties In Nanostructured Fe/Ag Composite Films, Y.Z. Zhang, Sy_Hwang Liou, R.J. Deangelis, K.W. Lee, C.P. Reed, A. Nazareth
Sy-Hwang Liou Publications
Nanostructured Fe/Ag composite films were prepared by magnetron sputtering using a single target. Correlations between the microstructure and magnetic properties, in particular the effects of cluster-size distribution in the films, are discussed. The cluster-size distribution was calculated by analyzing the width and shape of the x-ray-diffraction peaks. The average cluster size in the films increased from 42 to 295 Å and from 38 to 320 Å in the systems of 41 and 27 vol % of Fe, respectively, as the substrate temperature increased from 100 to 500 °C. The maximum magnetic coercivity, as high as 900 Oe, has been observed …
Effect Of Interfacial Microstructure On Magnetic Properties Of Dysprosium Multilayers, Z.S. Shan, B. Jacobsen, Sy_Hwang Liou, David J. Sellmyer
Effect Of Interfacial Microstructure On Magnetic Properties Of Dysprosium Multilayers, Z.S. Shan, B. Jacobsen, Sy_Hwang Liou, David J. Sellmyer
Sy-Hwang Liou Publications
Nanostructured multilayers of Dy/M (M=Ta, Cu, Y, and Co) have been investigated. Correlations between the microstructure and the magnetic properties, in particular the effects of interfacial structure, are discussed. The temperature and layer-thickness dependences of anisotropy of these Dy/M multilayers can be interpreted reasonably in light of the model previously developed for the perpendicular anisotropy in amorphous multilayers.
Spacetime Dimension From A Variational Principle, D. Hochberg, James Thomas Wheeler
Spacetime Dimension From A Variational Principle, D. Hochberg, James Thomas Wheeler
All Physics Faculty Publications
We consider spacetime as having an a priori arbitrary, possibly fractional dimension p>0 and propose a new variational principle for actions defined on p-dimensional spaces. Demanding that the action be stationary with respect to variations in p leads to a constraint equation whose solution yields an explicit determination of the dimension at the classical level. We illustrate these concepts by analyzing a model which reduces to free scalar field theory when p is any positive integer.
Magneto-Optic Properties Of Uranium-Based Compounds, Roger D. Kirby, J. X. Shen, John A. Woollam, David J. Sellmyer
Magneto-Optic Properties Of Uranium-Based Compounds, Roger D. Kirby, J. X. Shen, John A. Woollam, David J. Sellmyer
Roger Kirby Publications
Uranium-based compounds often show interesting magnetic properties and large polar Kerr rotations. Because of this, the wavelength and temperature dependencies of the polar Kerr rotation in several uranium-based compounds, including UMn2Ge2, UFe2, and UGa2, have been investigated. The Mn moments order ferromagnetically in UMn2Ge2 below 380 K, and while the U moments do not order ferromagnetically until the temperature is below 150 K. The measurements presented here show that the size of the Kerr rotation increases from 0.05° at room temperature to 0.15° when the U moments are ordered. …
Observation Of The Photorefractive Effect In A Polymer, Stephen Ducharme, J.C. Scott, R.J. Twieg, W.E. Moerner
Observation Of The Photorefractive Effect In A Polymer, Stephen Ducharme, J.C. Scott, R.J. Twieg, W.E. Moerner
Stephen Ducharme Publications
We report the first observation of the photorefractive effect in a polymeric material, the electro-optic polymer bisphenol-A-diglycidylether 4-nitro-1,2-phenylenediamine made photoconductive by doping with the hole-transport agent diethylamino-benzaldehyde diphenylhydrazone. The gratings formed exhibit dynamic writing and erasure, strong electric-field dependence, polarization anisotropy, and estimated space-charge fields up to 26 kV/cm at an applied field of 126 kV/cm. Application of similar concepts should provide a broad new class of easily fabricated photorefractive materials.
Removal Of Chlorine From Chlorine-Nitrogen Mixture In A Film Of Liquid Water, Sarwan S. Sandhu
Removal Of Chlorine From Chlorine-Nitrogen Mixture In A Film Of Liquid Water, Sarwan S. Sandhu
Chemical and Materials Engineering Faculty Publications
In industry there are many examples of absorption of a gas with or without chemical reaction in the liquid phase. In physical absorption, a particular gaseous component is removed from a gas mixture due to its larger solubility in the liquid phase solvent. The removal of butane and pentane from a refinery gas mixture by a heavy oil in the liquid phase is an example of physical absorption. In absorption with chemical reaction, the gaseous component to be removed transfers across the gas-liquid interface due to a difference in the bulk chemical potentials or concentrations in the two phases. The …
Extrapolation Of The Experimental Data Of Electron Scattering, Hansen Chen
Extrapolation Of The Experimental Data Of Electron Scattering, Hansen Chen
Opportunities for Undergraduate Research Experience Program (OURE)
Our problem of interest is electron-atom scattering. One type of experiment is to measure the number of electrons exciting an atom from a initial s-state to a final p-state. These measurements are proportional to the differential cross section (DCS)….
The plane wave Bom approximation is known not to be accurate enough. However Lassetre claims that even if PWBA (plane wave Bom approximation) is not reliable, a more accurate theory should still extrapolate to the optical oscillator strength.
The theory we are using is significantly better than the PWBA. According to Lassetre’s theorem, our theory should extrapolate to the optical oscillator …
Nonlinear Dynamics And The Lorenz Water Wheel, Richard Margis
Nonlinear Dynamics And The Lorenz Water Wheel, Richard Margis
Opportunities for Undergraduate Research Experience Program (OURE)
Undoubtedly one of the most exciting frontiers in physics today is the study of nonlinear systems, more popularly called chaos. Chaos is the key to many time-dependent processes in as varied fields as meteorology (such as weather modeling), mechanics (the three-body problem in gravitational fields), and economics (prediction of trends in the stock market).
Biological Effectiveness Of High-Energy Protons: Target Fragmentation, Francis A. Cucinotta, Robert Katz, John W. Wilson, Lawrence W. Townsend, Judy Shinn, Ferenc Hajnal
Biological Effectiveness Of High-Energy Protons: Target Fragmentation, Francis A. Cucinotta, Robert Katz, John W. Wilson, Lawrence W. Townsend, Judy Shinn, Ferenc Hajnal
Robert Katz Publications
High-energy protons traversing tissue produce local sources of high-linear-energy-transfer (LET) ions through nuclear fragmentation. We examine the contribution of these target fragments to the biological effectiveness of high-energy protons using the cellular track model. The effects of secondary ions are treated in terms of the production collision density using energy-dependent parameters from a high-energy fragmentation model. Calculations for mammalian cell cultures show that at high dose, at which intertrack effects become important, protons deliver damage similar to that produced by γ rays, and with fragmentation the relative biological effectiveness (RBE) of protons increases moderately from unity. At low dose, where …
Degnerate Four-Wave Mixing In Rhodamine Doped Epoxy Waveguides, B. Rossi, Hugh Byrne, W. Blau
Degnerate Four-Wave Mixing In Rhodamine Doped Epoxy Waveguides, B. Rossi, Hugh Byrne, W. Blau
Articles
Self-diffraction from laser-induced gratings is observed in a 13 pm-thick film of rhodamine I3 doped epoxy. The decay of the grating is measured to be 2.05 ns. Degenerate forward four-wave mixing in a guided geometry is observed by coupling out all beams after nronagation over 1 mm. At 595 nm the third-order nonlinear susceptibility of the film is measured to be 1.5~10-‘~ m2Ve2.
Intraconfiguration Interactions In Barium 6p1/2Nf Autoionizing States, Xiao Wang, J. Greg Story, William E. Cooke
Intraconfiguration Interactions In Barium 6p1/2Nf Autoionizing States, Xiao Wang, J. Greg Story, William E. Cooke
Physics Faculty Research & Creative Works
Measurements are reported of the energies and linewidths of the J=2, 3, and 4 components of the 6p1/214f and 6p1/219f states of barium. These states are anomalously broad, having autoionization lifetimes of approximately 1/2 of a classical Rydberg orbit period, and previously measurements have discerned no differences among the various J components. This work shows that the differences can be observed, and are consistent with calculations. The variations between states would be large if the states were LS coupled, but the large 6p ionic fine-structure forces recoupling into jj configurations. The spherical symmetry of the 6p …
Synchrotron-Radiation-Induced Deposition Of Boron And Boron Carbide Films From Boranes And Carboranes: Decaborane, F. Keith Perkins, R.A. Rosenberg, Sunwoo Lee, Peter A. Dowben
Synchrotron-Radiation-Induced Deposition Of Boron And Boron Carbide Films From Boranes And Carboranes: Decaborane, F. Keith Perkins, R.A. Rosenberg, Sunwoo Lee, Peter A. Dowben
Peter Dowben Publications
Boron has been deposited successfully on Si(111) from the synchrotron-radiation-induced decomposition of decaborane (14), i.e., B10H14. The rate of deposition is limited by the adsorption rate of decaborane (14) on the surface. In addition there is some indication that there is an activation barrier to dissociative adsorption. The synchrotron-radiation- induced growth rate of boron thin films from decaborane (14) is linear with coverage for a large range of thickness, suggesting a constant sticking coefficient for decaborane adsorption at room temperature.
Molecular-Orbital Studies Via Satellite-Free X-Ray Fluorescence: Cl-K Absorption And K–Valence-Level Emission Spectra Of Chlorofluoromethanes, Rupert C. Perera, P. L. Cowan, Dennis W. Lindle, R. E. Lavilla, T. Jach, R. D. Deslattes
Molecular-Orbital Studies Via Satellite-Free X-Ray Fluorescence: Cl-K Absorption And K–Valence-Level Emission Spectra Of Chlorofluoromethanes, Rupert C. Perera, P. L. Cowan, Dennis W. Lindle, R. E. Lavilla, T. Jach, R. D. Deslattes
Chemistry and Biochemistry Faculty Research
X-ray absorption and emission measurements in the vicinity of the chlorine K edge of the three chlorofluoromethanes have been made using monochromatic synchrotron radiation as the source of excitation. By selectively tuning the incident radiation to just above the Cl 1s single-electron ionization threshold for each molecule, less complex x-ray-emission spectra are obtained. This reduction in complexity is attributed to the elimination of multielectron transitions in the Cl K shell, which commonly produce satellite features in x-ray emission. The resulting "satellite-free" x-ray-emission spectra exhibit peaks due only to electrons in valence molecular orbitals filling a single Cl 1s vacancy. These …
Transport Anomalies In The High-Temperature Hopping Conductivity And Thermopower Of Sr-Doped La(Cr,Mn)O,₃, Ryne P. Raffaelle, Harlan U. Anderson, Don M. Sparlin, Paul Ernest Parris
Transport Anomalies In The High-Temperature Hopping Conductivity And Thermopower Of Sr-Doped La(Cr,Mn)O,₃, Ryne P. Raffaelle, Harlan U. Anderson, Don M. Sparlin, Paul Ernest Parris
Materials Science and Engineering Faculty Research & Creative Works
A minimum exists in the electrical conductivity of the perovskite-type ceramic LaCr1-xMnxO3 as a function of Mn content near x=0.05. This minimum has been explained in terms of a crossover from multiple trapping to percolation among energetically lower Mn sites. In this paper electrical conductivity and Seebeck measurements are presented on a similar series in which 10 mol % Sr was substituted for La in order to increase the small polaron concentration through the compensation of Sr ions according to the Verway mechanism. The data suggests that there is an apparent suppression of the Verway …