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1993

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Full-Text Articles in Physics

A Theoretical Investigation Of The Geometries, Vibrational Frequencies, And Binding Energies Of Several Mixed Alkali Halide Dimers, Robert J. Cave, Ian Ono '94 Dec 1993

A Theoretical Investigation Of The Geometries, Vibrational Frequencies, And Binding Energies Of Several Mixed Alkali Halide Dimers, Robert J. Cave, Ian Ono '94

All HMC Faculty Publications and Research

Results are presented from ab initio calculations on several mixed alkali halide dimers made up of Li, Na, F, and Cl. All of the dimers are investigated at the restricted Hartree–Fock level to provide ab initio estimates of geometries, vibrational frequencies, and binding energies. The dimer LiNaF2 is then treated using a variety of basis sets at the Hartree–Fock level, as well as at correlated levels (second‐order Møller–Plesset and coupled‐cluster singles and doubles) to examine the sensitivity of the calculations to use of higher levels of theory. The results are then compared to the experimental ...


Evidence For Day-To-Night Ion Transport At Low Solar Activity In The Venus Pre-Dawn Ionosphere, J. F. Brannon, Jane L. Fox, H. S. Porter Dec 1993

Evidence For Day-To-Night Ion Transport At Low Solar Activity In The Venus Pre-Dawn Ionosphere, J. F. Brannon, Jane L. Fox, H. S. Porter

Physics Faculty Publications

Periapsis of the Pioneer Venus spacecraft dropped below 180 km on August 28, 1992 near midnight, and 42 orbits of low altitude data at moderately low solar activity in the pre-dawn sector were obtained before contact was lost to the spacecraft in October, 1992. Through a combination of analysis of data from the PV orbiter ion mass spectrometer (OIMS) and modeling, we consider here what can be learned about the relative importance of plasma transport from the dayside and electron precipitation in maintaining the nightside ionosphere during the re-entry period. In particular, we examine here the atomic ion density profiles ...


Neutron Reflection Interferometry: Physical Principles Of Surface Analysis With Phase Information, Vladimir Gudkov, G. I. Opat, A. G. Klein Dec 1993

Neutron Reflection Interferometry: Physical Principles Of Surface Analysis With Phase Information, Vladimir Gudkov, G. I. Opat, A. G. Klein

Faculty Publications

It is shown that the analysis of surface layers by neutron reflection interferometry is considerably enhanced by performing the reflectometry with phase information. We discuss two methods of providing such information. One method involves physically adding an extra reference layer, whose amplitude and phase are known theoretically. The other uses the Lloyd's mirror configuration, in which a directly propagating ray that interferes with the reflected ray supplies the phase information. The methods have much in common with holography.


Short Terahertz Pulses From Semiconductor Surfaces: The Importance Of Bulk Difference‐Frequency Mixing, Peter N. Saeta, Benjamin I. Greene, Shun Lien Chuang Dec 1993

Short Terahertz Pulses From Semiconductor Surfaces: The Importance Of Bulk Difference‐Frequency Mixing, Peter N. Saeta, Benjamin I. Greene, Shun Lien Chuang

All HMC Faculty Publications and Research

The crystallographic orientation dependence of the far‐infrared (FIR) light generated at the (001) surface of a zincblende semiconductor is shown to derive principally from bulk difference‐frequency mixing. A strong modulation is observed for 1‐GW/cm2 pulses on InP, which demonstrates that the radiated FIR wave produced by bulk optical rectification is comparable to that generated by the transport of photoinjected carriers. Using the bulk rectification light as a clock, we show that more than 95% of the light produced from an InP (111) crystal by 100‐fs, 100‐μJ pulses is generated in a time shorter ...


A Random Wave Method For Detecting Phase Imbalance In A Coherent Radar Receiver, Zhenni Wang, Alexander Kostinski Dec 1993

A Random Wave Method For Detecting Phase Imbalance In A Coherent Radar Receiver, Zhenni Wang, Alexander Kostinski

Department of Physics Publications

The question of monitoring the angle between the in-phase (I) and quadrature (Q) channels of a coherent radar receiver is considered in this paper. Random interference-type scattering (e.g., rain echo) is assumed so that the received signal is a random phasor sum. It is also assumed that I and Q voltages have a (90 + ϕ0) phase difference. The effects of nonzero phase imbalance ϕ0 on the I and Q statistics are examined. Joint I and Q as well as amplitude and phase probability distributions are derived. It is shown that the cross-correlation coefficient at zero lag between ...


Recombination Of 2-Dimensional Electrons With Free Light And Heavy Holes In Alxga1-Xas-Gaas Single Heterojunctions In A Magnetic-Field, D. C. Reynolds, David C. Look, B. Jogai, C. E. Stutz Dec 1993

Recombination Of 2-Dimensional Electrons With Free Light And Heavy Holes In Alxga1-Xas-Gaas Single Heterojunctions In A Magnetic-Field, D. C. Reynolds, David C. Look, B. Jogai, C. E. Stutz

Physics Faculty Publications

Landau-level oscillations are observed in the photoluminescence from an AlxGa1-xAs-GaAs single heterojunction in an applied magnetic field. Extrapolating the oscillations back to zero field gives the energy of the transition from the two-dimensional (2D) electrons to the free heavy holes (hh1 and hh2) and free light holes (lh) weakly confined in the GaAs active layer. The measured energy separation between hh1 and lh is 1.8 meV, which agrees very well with the calculated value of 2.2 meV. The measured energy separation between hh1 and hh2 is 3.8 meV, in good agreement with the ...


Rock Magnetic Criteria For The Detection Of Biogenic Magnetite, Bruce M. Moskowitz, Richard B. Frankel, Dennis A. Bazylinski Dec 1993

Rock Magnetic Criteria For The Detection Of Biogenic Magnetite, Bruce M. Moskowitz, Richard B. Frankel, Dennis A. Bazylinski

Physics

We report results on the magnetic properties of magnetites produced by magnetotactic and dissimilatory iron-reducing bacteria. Magnetotactic bacterial (MTB) strains MS1, MV1 and MV2 and dissimilatory iron-reducing bacterium strain GS-15, grown in pure cultures, were used in this study. Our results suggest that a combination of room temperature coercivity analysis and low temperature remanence measurements provides a characteristic magnetic signature for intact chains of single domain (SD) particles of magnetite from MTBs. The most useful magnetic property measurements include: (1) acquisition and demagnetization of isothermal remanent magnetization (IRM) using static, pulse and alternating fields; (2) acquisition of anhysteretic remanent magnetization ...


Lattice-Dynamical Study Of The Premartensitic State Of The Cu-Al-Be Alloys, Lluís Mañosa, Jerel L. Zarestky, Thomas A. Lograsso, Dwight W. Delaney, C. Stassis Dec 1993

Lattice-Dynamical Study Of The Premartensitic State Of The Cu-Al-Be Alloys, Lluís Mañosa, Jerel L. Zarestky, Thomas A. Lograsso, Dwight W. Delaney, C. Stassis

Ames Laboratory Publications

Neutron-scattering techniques have been used to study the premartensitic state of a family of Cu-Al-Be alloys, which transform from the bcc phase to an 18R martensitic structure. We find that the phonon modes of the TA2[110] branch have very low energies with anomalous temperature dependence. A slight anomaly at q=2/3 was observed; this anomaly, however, does not change significantly with temperature. No elastic peaks, related to the martensite structure, were found in the premartensitic state of these alloys. The results are compared with measurements, performed under the same instrumental conditions, on two Cu-Al-Ni and a Cu-Zn-Al ...


Neutron-Diffraction And Mössbauer-Effect Studies Of Pr2(Fe1-XMnX)14B, Oran Allan Pringle, Jie Fu, Gary J. Long, William Joseph James, Decai Xie, William B. Yelon, Fernande Grandjean Dec 1993

Neutron-Diffraction And Mössbauer-Effect Studies Of Pr2(Fe1-XMnX)14B, Oran Allan Pringle, Jie Fu, Gary J. Long, William Joseph James, Decai Xie, William B. Yelon, Fernande Grandjean

Physics Faculty Research & Creative Works

A neutron-diffraction investigation of a series of Pr2(Fe 1-xMnx)14B samples, with x values of 0.00, 0.11, 0.22, 0.30, and 0.35, reveals a preference for the manganese to occupy the 8j2 transition-metal site,the transition-metal site with the largest Wigner-Seitz cell volume. Similar site occupancies have been reported previously for Er2(Fe1-xMnx) 14B and Y2(Fe1-xMnx) 14B. An analysis of the 295-K Mössbauer spectrum of Pr2(Fe0.89Mn0.11)14B indicates that the internal ...


Giant Energy Product In Nanostructured Two-Phase Magnets , Ralph Skomski, J.M.D. Coey Dec 1993

Giant Energy Product In Nanostructured Two-Phase Magnets , Ralph Skomski, J.M.D. Coey

Ralph Skomski Publications

Exchange hardening of nanostructured two-phase systems composed of an aligned hard phase and a soft phase with high magnetization is investigated using an approach which yields analytic nucleation fields from the micromagnetic vector equation, and accounts for interactions between the soft regions. In suitable structures the nucleation field is proportional to the volume-averaged anisotropy constant. For example, a multilayer composed of alternating 2.4 nm hard-magnetic Sm2Fe17N3 layers and 9 nm Fe65Co35 layers can have an energy product as high as 1 MJ/m3 (120 MG Oe), with a rare-earth content ...


The Behlen Observatory Variable Star Survey: Finding Charts And Light Curves For The First Ninety-Three Stars, Edward G. Schmidt, Darwin E. Reiswig Dec 1993

The Behlen Observatory Variable Star Survey: Finding Charts And Light Curves For The First Ninety-Three Stars, Edward G. Schmidt, Darwin E. Reiswig

Edward Schmidt Publications

In a previous paper, photometry for the first ninety-three stars in a photometric survey of variable stars was discussed. Finding charts, accurate coordinates, and light curves for those stars are presented here. The reliability of the coordinates from the General Catalogue of Variable Stars is discussed. The magnitude scale of the present photometry is compared with that of the Hubble Space Telescope Guide Star Catalogue.


Far-Ultraviolet Stellar Photometry: A Field In Orion, Edward G. Schmidt, George R. Carruthers Dec 1993

Far-Ultraviolet Stellar Photometry: A Field In Orion, Edward G. Schmidt, George R. Carruthers

Edward Schmidt Publications

Far-ultraviolet photometry for 625 objects in Orion is presented. These data were extracted from electrographic camera images obtained during sounding rocket flights in 1975 and 1982. The 1975 images were centered close to the belt of Orion while the 1982 images were centered ~9° further north. One hundred and fifty stars fell in the overlapping region and were observed with both cameras. Sixty-eight percent of the objects were tentatively identified with known stars using the SIMBAD database while another 24% are blends of objects too close together to separate with our resolution. As in previous studies, the majority of the ...


The Structural Homogeneity Of Boron Carbide Thin Films Fabricated Using Plasma-Enhanced Chemical Vapor Deposition From B5H9+Ch4, Sunwoo Lee, J. Mazurowski, W.L. O'Brien, Q.Y. Dong, J.J. Jia, T.A. Callcott, K.E. Miyano, D.L. Ederer, D.R. Mueller, Peter A. Dowben Dec 1993

The Structural Homogeneity Of Boron Carbide Thin Films Fabricated Using Plasma-Enhanced Chemical Vapor Deposition From B5H9+Ch4, Sunwoo Lee, J. Mazurowski, W.L. O'Brien, Q.Y. Dong, J.J. Jia, T.A. Callcott, K.E. Miyano, D.L. Ederer, D.R. Mueller, Peter A. Dowben

Peter Dowben Publications

Boron carbide thin films of several B/C ratios have been deposited on Si(111) using plasma-enhanced chemical vapor deposition from nido-pentaborane(9) (B5H9) and methane (CH4). X-ray diffraction studies of boron carbide thin films on Si(111) exhibited characteristic microcrystalline diffraction lines. Soft x-ray emission spectroscopy was used to verify that the local electronic structure and composition of each sample corresponded to a homogeneous solid solution boron carbide phase.


Onset Of Convection For Autocatalytic Reaction Fronts In A Vertical Slab, J. Huang, D. A. Vasquez, Boyd F. Edwards, P. Kolodner Dec 1993

Onset Of Convection For Autocatalytic Reaction Fronts In A Vertical Slab, J. Huang, D. A. Vasquez, Boyd F. Edwards, P. Kolodner

All Physics Faculty Publications

A fully three-dimensional linear stability analysis shows that ascending autocatalytic reaction fronts in vertical slabs are unstable to convection for large-wavelength perturbations at all finite values of the dimensionless driving parameter S=δga3/νDC. This parameter involves a fractional density difference δ between the unreacted and reacted fluids, the acceleration of gravity g, the slab width a, the kinematic viscosity ν, and the catalyst molecular diffusivity DC. Buoyancy dominates over the competing curvature dependence of the front velocity in a band 0c of unstable dimensionless wave numbers, with qc→S/24 as S→0 and q ...


Critical Slowing Down Of Cluster Algorithms For Ising Models Coupled To 2-D Gravity, Mark Bowick, Marco Falcioni, Geoffrey Harris, Enzo Marinari Nov 1993

Critical Slowing Down Of Cluster Algorithms For Ising Models Coupled To 2-D Gravity, Mark Bowick, Marco Falcioni, Geoffrey Harris, Enzo Marinari

Physics

We simulate single and multiple Ising models coupled to 2-d gravity using both the Swendsen-Wang and Wolff algorithms to update the spins. We study the integrated autocorrelation time and find that there is considerable critical slowing down, particularly in the magnetization. We argue that this is primarily due to the local nature of the dynamical triangulation algorithm and to the generation of a distribution of baby universes which inhibits cluster growth.


The Chemical Evolution Of Qsos And The Implications For Cosmology And Galaxy Formation, Fred Hamann, Gary J. Ferland Nov 1993

The Chemical Evolution Of Qsos And The Implications For Cosmology And Galaxy Formation, Fred Hamann, Gary J. Ferland

Physics and Astronomy Faculty Publications

We examine the chemical evolution of QSO broad-line gas by applying spectral synthesis and chemical enrichment models to the N V/C IV and N V/He II emission-line ratios. The models indicate that BLR metallicities are typically ~1 to perhaps ≳10 times solar. The enrichment must occur in ≲1 Gyr for sources where the redshift is ≳3 (if q0 = ½). The higher metallicity QSOs require star formation favoring massive stars (compared to the Galactic disk). These results imply that extensive evolution usually occurs before the QSOs become observable. Our models of the evolution are equivalent to models proposed ...


Fe304 And Fe3S4 In A Bacterium, Dennis A. Bazylinski, Brigid R. Heywood, Stephen Mann, Richard B. Frankel Nov 1993

Fe304 And Fe3S4 In A Bacterium, Dennis A. Bazylinski, Brigid R. Heywood, Stephen Mann, Richard B. Frankel

Physics

No abstract provided.


Response To "Comment On 'The Weakest Bond: Experimental Observation Of Helium Dimer'", Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, Ronald Gentry Nov 1993

Response To "Comment On 'The Weakest Bond: Experimental Observation Of Helium Dimer'", Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, Ronald Gentry

Peer Reviewed Articles

No abstract provided.


Microphysical Approach To Nonequilibrium Dynamics Of Quantum Fields, Marcelo Gleiser, Rudnei O. Ramos Nov 1993

Microphysical Approach To Nonequilibrium Dynamics Of Quantum Fields, Marcelo Gleiser, Rudnei O. Ramos

Open Dartmouth: Faculty Open Access Scholarship

We examine the nonequilibrium dynamics of a self-interacting λφ4 scalar field theory. Using a real time formulation of finite temperature field theory we derive, up to two loops and O(λ2), the effective equation of motion describing the approach to equilibrium. We present a detailed analysis of the approxi- mations used in order to obtain a Langevin-like equation of motion, in which the noise and dissipation terms associated with quantum fluctuations obey a fluctuation-dissipation relation. We show that, in general, the noise is colored (time-dependent) and multiplicative (couples nonlinearly to the field), even though it is still Gaussian distributed. The ...


Radial Excited States For Heavy Quark Systems In Nrqcd, Simon Catterall, F. R. Devlin, I. T. Drummond, R. R. Hogan Nov 1993

Radial Excited States For Heavy Quark Systems In Nrqcd, Simon Catterall, F. R. Devlin, I. T. Drummond, R. R. Hogan

Physics

Following the Non-Relativistic QCD approach we use a gauge invariant smearing method with factorization to measure the excitation energies for a heavy Q\bar{Q} system on a 24^3\times 48 lattice at \beta=6.2. The results come from averaging over an ensemble of 60 QCD configurations. In order to enhance the signal from each configuration we use wall sources for quark propagators. The quark Hamiltonian contains only the simplest non-relativistic kinetic energy term. The results are listed for a range of bare quark masses. The mass splittings are insensitive to this variable though there are a slight ...


Coherent Versus Incoherent Ladar Detection At 2.09 Μm, Jay A. Overbeck, Martin B. Mark, Scott H. Mccraken, Paul F. Mcmanamon, Bradley D. Duncan Nov 1993

Coherent Versus Incoherent Ladar Detection At 2.09 Μm, Jay A. Overbeck, Martin B. Mark, Scott H. Mccraken, Paul F. Mcmanamon, Bradley D. Duncan

Electro-Optics and Photonics Faculty Publications

A 2.09-μm ladar system is built to compare coherent to incoherent detection. The 2.09-μm wavelength is of interest because of its high atmospheric transmission and because it is eyesafe. The 2.09-μm system presented is capable of either a coherent or incoherent operational mode, is tunable in a small region around 2.09 μm, and is being used to look at the statistical nature of the ladar return pulses for typical glint and speckle targets. To compare coherent to incoherent detection the probability of detection is investigated as the primary performance criterion of interest. The probability of detection ...


Sensitivity Improvement Of A 1-Μm Ladar System Incorporating An Active Optical Fiber Preamplifier, Michael S. Salisbury, Paul F. Mcmanamon, Bradley D. Duncan Nov 1993

Sensitivity Improvement Of A 1-Μm Ladar System Incorporating An Active Optical Fiber Preamplifier, Michael S. Salisbury, Paul F. Mcmanamon, Bradley D. Duncan

Electro-Optics and Photonics Faculty Publications

In an effort to increase the SNR of a continuous wave, 1-μm all solid state ladar system, a rare-earth-doped optical fiber amplifier is investigated as a preamplifier for ladar return signals. The experimental system is detailed and a theoretical analysis of the fiber amplifier's effect on both heterodyne and direct detection schemes is provided. Beginning with the optical powers incident on the detector, the signal and noises are analyzed, through the detector electronics, to predict the SNR. The SNR is then plotted as a function of the return signal power, and a SNR threshold is defined to determine a ...


Cation Distribution In Natural Ferrites, H. A. Maia, F. F. T. De Araújo, M. A. B. De Araújo, J. Danon, Richard B. Frankel Nov 1993

Cation Distribution In Natural Ferrites, H. A. Maia, F. F. T. De Araújo, M. A. B. De Araújo, J. Danon, Richard B. Frankel

Physics

Mössbauer spectra of jacobsite have been recorded at temperatures of 4.2, 125, 180, 240 and 300 K and with an external magnetic field of 60 kOe applied parallel to the incident radiation at 4.2 K. The results show the presence of two different magnetic hyperfine interactions associated with the iron nuclei. Spectra of samples in external magnetic fields indicate the same sign for the magnetic hyperfine interactions, implying that both iron ions occupy only the octahedral sublattice. These results are compared with data from synthetic stoichiometry manganese ferrite, and a model of cation distribution, assuming the existence of ...


Photodetachment Of The 2P2 (3PE) State Of H-, Ning-Yi Du, Anthony F. Starace, Min-Qi Bao Nov 1993

Photodetachment Of The 2P2 (3PE) State Of H-, Ning-Yi Du, Anthony F. Starace, Min-Qi Bao

Anthony F. Starace Publications

Results of semiempirical, adiabatic hyperspherical calculations are presented for the photodetachment cross section of the process H- 2p2 (3Pe)+γ→H(n=2)+ e- at photon energies in the range from threshold to 0.125 a.u. above. We find the detachment cross section to have a maximum value of 482 Mb at 25.7 meV above threshold, in good agreement with results of close-coupling calculations by Jacobs, Bhatia, and Temkin [Astrophys. J. 242, 1278 (1980)]. In contrast to the close-coupling results, however, we find that the detachment cross section rises by a factor of more ...


Simulation Of Bulk Silicon Crystals And Si(111) Surfaces With Application To A Study Of Fluorine Coverage Of The Surfaces, Chen K. Lutrus, T. Oshiro, Donald E. Hagen, Sung-Ho Suck Salk Nov 1993

Simulation Of Bulk Silicon Crystals And Si(111) Surfaces With Application To A Study Of Fluorine Coverage Of The Surfaces, Chen K. Lutrus, T. Oshiro, Donald E. Hagen, Sung-Ho Suck Salk

Physics Faculty Research & Creative Works

Computational efficiency for the simulation of bulk crystals and surfaces is highly desirable. In an effort to study semiconductor crystals, we present a self-consistent treatment for the simulation of silicon crystals and surfaces based on the combination of a siligen model and a semiempirical Hamiltonian method. An artificial atom called siligen is introduced for the application of the semiempirical method to finite-size silicon clusters. The calculated average bond energies for the saturated silicon clusters are between 2.045 and 2.568 eV, compared to the measured value of 2.31 eV. A simulated bulk silicon surface using siligens is introduced ...


Neutron-Diffraction And Mössbauer Effect Study Of The Preferential Silicon Site Occupation And Magnetic Structure Of Nd2Fe14-XSiXB, Gaya Kanishka Marasinghe, Oran Allan Pringle, Gary J. Long, William Joseph James, Dianne J. Xiao, J. L. Li, William B. Yelon, Fernande Grandjean Nov 1993

Neutron-Diffraction And Mössbauer Effect Study Of The Preferential Silicon Site Occupation And Magnetic Structure Of Nd2Fe14-XSiXB, Gaya Kanishka Marasinghe, Oran Allan Pringle, Gary J. Long, William Joseph James, Dianne J. Xiao, J. L. Li, William B. Yelon, Fernande Grandjean

Physics Faculty Research & Creative Works

A neutron-diffraction study of Nd2Fe14-xSixB has shown that silicon preferentially occupies the 4c site in the transition-metal sublattice in Nd2Fe14B. Silicon also exhibits a moderate preference for the 8j1 site, is almost excluded from the 16k2 site, and avoids the 16k1, 8j2, and 4e sites. The silicon site occupancy is correlated with a preference for a silicon atom to have rare-earth atoms in its coordination environment. The Mössbauer spectra of Nd2Fe14-xSixB have been fit with a model which takes into ...


Spatially Resolved Transitions To Autoionizing States, J. Greg Story, D. I. Duncan, Thomas F. Gallagher Nov 1993

Spatially Resolved Transitions To Autoionizing States, J. Greg Story, D. I. Duncan, Thomas F. Gallagher

Physics Faculty Research & Creative Works

We have observed transitions to autoionizing states in Mg using two short optical pulses. Mg atoms are initially prepared in a high lying Rydberg wave packet with the first ps laser. A second ps laser is then used to excite the inner electron, producing an autoionizing state. The dependence of the transition probability on the delay between the two lasers shows that when the second laser is tuned away from the ionic resonance, the inner electron can make a transition only when the Rydberg wave packet is near the core.


Large-Cell Renormalization-Group Approach To Long-Range Hopping On Energetically Disordered Lattices, B. D. Bookout, Paul Ernest Parris Nov 1993

Large-Cell Renormalization-Group Approach To Long-Range Hopping On Energetically Disordered Lattices, B. D. Bookout, Paul Ernest Parris

Physics Faculty Research & Creative Works

We describe an approach for computing the conductivity associated with long-range hopping on energetically disordered lattices. Using a numerically exact supercell procedure we compute the distribution ρL(γ) of block conductances γL associated with conducting cubes of edge length L that are randomly chosen from the disordered system of interest. This distribution of block conductances is then used in a self-consistent numerical calculation to obtain the renormalized bulk conductivity. The approach displays a surprisingly fast approach to the infinite-system limit, allowing finite-size effects to be minimized. In this paper we use this approach to study transport in a series of ...


The Temperature Dependence Of Perpendicular Anisotropy In Co/Pt And Co/Au Multilayer Films, H.Y. Zhang, Y.J. Wang, G.G. Zheng, J.X. Shen, Z.S. Shan, David J. Sellmyer Nov 1993

The Temperature Dependence Of Perpendicular Anisotropy In Co/Pt And Co/Au Multilayer Films, H.Y. Zhang, Y.J. Wang, G.G. Zheng, J.X. Shen, Z.S. Shan, David J. Sellmyer

David Sellmyer Publications

We report the temperature dependence of the effective perpendicular anisotropy and interface anisotropy in the temperature region of 80K to 290K for Co/Pt and Co/Au multilayers. Different temperature dependence of the interface anisotropy have been observed for these two types of multilayers. We speculate that the strain due to the lattice misfit may not be the main reason responsible for the perpendicular anisotropy in Co/Pt and Co/Au multilayers.


Structural And Magnetic Properties Of Lafe13-XSiX Nitrides, Z.X. Tang, X.H. Deng, George C. Hadjipanayis, V. Papaefthymiou, David J. Sellmyer Nov 1993

Structural And Magnetic Properties Of Lafe13-XSiX Nitrides, Z.X. Tang, X.H. Deng, George C. Hadjipanayis, V. Papaefthymiou, David J. Sellmyer

David Sellmyer Publications

LaFe13-xSix compounds were found to have two types of crystal structure; the face-centered cubic Na13--type (x ≤2.4) and the body-centered tetragonal Ce2Ni17Si9-type (3.5≤x≤5.0). Nitrogenation has a strong effect on the cubic phase, including a large lattice expansion (6.2 to 10.8 %), an increase of Curie temperature (52 to 80 K) and spontaneous magnetization ( ~10 %). The tetragonal phase, however, was not significantly affected by the nitrogenation.