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2015-03-19
Bit Patterned Magnetic Recording: Theory, Media Fabrication, and Recording Performance
Bit Patterned Media (BPM) for magnetic recording provide a route to densities $>1 Tb/in^2$ and circumvents many of the challenges associated with conventional granular media technology. Instead of recording a bit on an ensemble of random grains, BPM uses an array of lithographically defined isolated magnetic islands, e...
1503.06664v1
2019-02-26
The Evidence of Cathodic Micro-discharges during Plasma Electrolytic Oxidation Process
Plasma electrolytic oxidation (PEO) processing of EV 31 magnesium alloy has been carried out in fluoride containing electrolyte under bipolar pulse current regime. Unusual PEO cathodic micro-discharges have been observed and investigated. It is shown that the cathodic micro-discharges exhibit a collective intermittent ...
1902.09828v1
2004-10-08
Total Mass of Ordinary Chondrite Matter Originally Present in the Solar System
Recently, I reported the discovery of a new fundamental relationship of the major elements (Fe, Mg, Si) of chondrites that admits the possibility that ordinary chondrite meteorites are derived from two components, a relatively oxidized and undifferentiated, primitive component and a somewhat differentiated, planetary c...
0410242v1
2006-02-10
Solar System Processes Underlying Planetary Formation, Geodynamics, and the Georeactor
Only three processes, operant during the formation of the Solar System, are responsible for the diversity of matter in the Solar System and are directly responsible for planetary internal-structures, including planetocentric nuclear fission reactors, and for dynamical processes, including and especially, geodynamics. T...
0602232v2
2006-12-01
Analytical scanning and transmission electron microscopy of laboratory impacts on Stardust aluminum foils: interpreting impact crater morphology and the composition of impact residues
The known encounter velocity (6.1kms-1) and particle incidence angle (perpendicular) between the Stardust spacecraft and the dust emanating from the nucleus of comet Wild 2 fall within a range that allows simulation in laboratory light gas gun experiments designed to validate analytical methods for the interpretation o...
0612013v1
1994-05-17
Chemical Reactions of Silicon Clusters
Smalley and co-workers discovered that chemisorption reactivities of silicon clusters vary over three orders of magnitude as a function of cluster size. In particular, they found that \Si{33}, \Si{39}, and \Si{45} clusters are least reactive towards various reagents compared to their immediate neighbors in size. We exp...
9405001v1
1994-01-07
Local Disorder in the Oxygen Environment Around Praseodymium in YBCO:Pr from X-ray Absorption Fine Structure
We present K-edge XAFS (X-Ray Absorption Fine Structure) data for various concentrations of Pr in Y$_{1- x}$Pr$_{x}$Ba$_{2}$Cu$_{3}$O$_{7}$. The character of the Pr K-edge XAFS data indicate that most of the Pr substitutes onto the Y site and is well ordered with respect to the unit cell. These data also show that the ...
9401014v1
1995-02-06
An Enhanced Perturbational Study on Spectral Properties of the Anderson Model
The infinite-$U$ single impurity Anderson model for rare earth alloys is examined with a new set of self-consistent coupled integral equations, which can be embedded in the large $N$ expansion scheme ($N$ is the local spin degeneracy). The finite temperature impurity density of states (DOS) and the spin-fluctuation spe...
9502020v1
1995-10-06
Universality class of non-Fermi liquid behavior in mixed valence systems
A generalized Anderson single-impurity model with off-site Coulomb interactions is derived from the extended three-band Hubbard model, originally proposed to describe the physics of the copper-oxides. Using the abelian bosonization technique and canonical transformations, an effective Hamiltonian is derived in the stro...
9510031v2
1997-10-17
The Role of Density of States Fluctuations in the Normal State Properties of High Tc Superconductors
HTS show many puzzling anomalies in their normal state properties. Among them are: - the presence of a peak in the c-axis resistance and its growth in external magnetic field - the anomalous negative magnetoresistance observed above Tc - the deviation from the Korringa law in the temperature dependence of the NMR...
9710175v2
1997-11-18
Effects of anharmonic strain on phase stability of epitaxial films and superlattices: applications to noble metals
Epitaxial strain energies of epitaxial films and bulk superlattices are studied via first-principles total energy calculations using the local-density approximation. Anharmonic effects due to large lattice mismatch, beyond the reach of the harmonic elasticity theory, are found to be very important in Cu/Au (lattice mis...
9711183v1
1997-12-12
Giant Thermomechanical Effect in Normal Liquid He-3
Measurements are presented of the thermomechanical coefficient of normal liquid He-3 confined in a porous plug pre-plated with four monoloyers of He-4. These non-magnetic monolayers displace the magnetic solid-like He-3 monolayers that are adjacent to the pore surfaces when the plug is filled with pure He-3. In the low...
9712144v1
1998-01-09
Evaluating and improving the cluster variation method entropy functional for Ising alloys
The success of the "Cluster Variation Method" (CVM) in reproducing quite accurately the free energies of Monte Carlo (MC) calculations on Ising models is explained in terms of identifying a cancellation of errors: We show that the CVM produces correlation functions that are too close to zero, which leads to an overesti...
9801080v1
1998-03-18
Mean-Field Study of the Degenerate Blume-Emery-Griffiths Model in a Random Crystal Field
The degenerate Blume-Emery-Griffiths (DBEG) model has recently been introduced in the study of martensitic transformation problems. This model has the same Hamiltonian as the standard Blume-Emery-Griffiths (BEG) model but, to take into account vibrational effects on the martensitic transition, it is assumed that the st...
9803220v1
1998-03-20
Dynamics of a ferromagnetic domain wall: avalanches, depinning transition and the Barkhausen effect
We study the dynamics of a ferromagnetic domain wall driven by an external magnetic field through a disordered medium. The avalanche-like motion of the domain walls between pinned configurations produces a noise known as the Barkhausen effect. We discuss experimental results on soft ferromagnetic materials, with refere...
9803253v1
1998-10-27
Fermionic Ising Glasses with BCS Pairing Interaction. Tricritical Behaviour
We have examined the role of the BCS pairing mechanism in the formation of the magnetic moment and henceforth a spin glass (SG) phase by studying a fermionic Sherrington-Kirkpatrick model with a local BCS coupling between the fermions. This model is obtained by using perturbation theory to trace out the conduction elec...
9810366v1
1998-11-30
Landau theory of bi-criticality in a random quantum rotor system
We consider here a generalization of the random quantum rotor model in which each rotor is characterized by an M-component vector spin. We focus entirely on the case not considered previously, namely when the distribution of exchange interactions has non-zero mean. Inclusion of non-zero mean permits ferromagnetic and s...
9811418v1
1998-12-07
The metal-insulator transition in amorphous Si_{1-x}Ni_x: Evidence for Mott's minimum metallic conductivity
We study the metal-insulator transition in two sets of amorphous Si_{1-x}Ni_x films. The sets were prepared by different, electron-beam-evaporation-based technologies: evaporation of the alloy, and gradient deposition from separate Ni and Si crucibles. The characterization included electron and scanning tunneling micro...
9812106v3
1999-01-28
An Efficient Molecular Dynamics Scheme for Predicting Dopant Implant Profiles in Semiconductors
We present a highly efficient molecular dynamics scheme for calculating the concentration profile of dopants implanted in group-IV alloy, and III-V zinc blende structure materials. Our program incorporates methods for reducing computational overhead, plus a rare event algorithm to give statistical accuracy over several...
9901338v1
1999-03-22
Superconductivity in heavy-fermion U(Pt,Pd)3 and its interplay with magnetism
The effect of Pd doping on the superconducting phase diagram of the unconventional superconductor UPt3 has been measured by (magneto)resistance, specific heat, thermal expansion and magnetostriction. Experiments on single- and polycrystalline U(Pt1-xPdx)3 for x<= 0.006 show that the superconducting transition temperatu...
9903333v1
1999-06-15
Electronic Structure of Cu_(1-x)Ni_xRh_2S_4 and CuRh_2Se_4: Band Structure Calculations, X-ray Photoemission and Fluorescence Measurements
The electronic structure of spinel-type Cu_(1-x)Ni_xRh_2S_4 (x = 0.0, 0.1, 0.3, 0.5, 1.0) and CuRh_2Se_4 compounds has been studied by means of X-ray photoelectron and fluorescent spectroscopy. Cu L_3, Ni L_3, S L_(2,3) and Se M_(2,3) X-ray emission spectra (XES) were measured near thresholds at Beamline 8.0 of the Law...
9906209v1
1999-12-02
Magnetic history dependence of metastable states in systems with dipolar interactions
We present the results of a Monte Carlo simulation of the ground state and magnetic relaxation of a model of a thin film consisting on a two-dimensional square lattice of Heisenberg spins with perpendicular anisotropy K, exchange J and long-range dipolar interactions g. We have studied the ground state configurations o...
9912025v2
1999-12-28
Effects of microscopic strain distribution on Ga(1-x)In(x)As quantum wires grown by strain-induced lateral ordering
Band Structures and optical matrix elements of quantum wires(QWR's) made of short-period superlattices(SPS) with strain-induced lateral ordering(SILO) are investigated theoretically via an effective bond-orbital model(EBOM) combined with a valence-force field(VFF) model. Valence-band anistropy, band mixing, and effects...
9912468v3
2000-03-02
Kinetics of Ordering in Fluctuation-Driven First-Order Transitions: Simulations and Dynamical Renormalization
Many systems where interactions compete with each other or with constraints are well described by a model first introduced by Brazovskii. Such systems include block copolymers, alloys with modulated phases, Rayleigh-Benard Cells and type-I superconductors. The hallmark of this model is that the fluctuation spectrum is ...
0003026v1
2000-08-03
Enhancement of Kondo Temperature in Nanometer-Size Point Contacts
Point-contact spectroscopy is applied to study the energy dependence of paramagnetic impurities in noble metals. The samples are in the form of the so-called "mechanically controllable break-junctions" where the investigated piece of alloy makes a nanowire connecting two bulk electrodes.The lateral dimensions of the br...
0008055v1
2000-08-17
Statics and dynamics of domain patterns in hexagonal-orthorhombic ferroelastics
We study the statics and the dynamics of domain patterns in proper hexagonal-orthorhombic ferroelastics; these patterns are of particular interest because they provide a rare physical realization of disclinations in crystals. Both our static and dynamical theories are based entirely on classical, nonlinear elasticity t...
0008256v1
2000-08-17
Fermionic Heisenberg Model for Spin Glasses with BCS Pairing Interaction
In the present paper we have analysed a fermionic infinite-ranged quantum Heisenberg spin glass (s=1/2) with a BCS coupling in real space in the presence of an applied magnetic field. This model has been obtained by tracing out the conducting fermions in a superconducting alloy. The magnetic field is applied in the res...
0008257v1
2000-10-03
Parquet approach to nonlocal vertex functions and electrical conductivity of disordered electrons
A diagrammatic technique for two-particle vertex functions is used to describe systematically the influence of spatial quantum coherence and backscattering effects on transport properties of noninteracting electrons in a random potential. In analogy with many-body theory we construct parquet equations for topologically...
0010044v1
2000-11-19
The relationship between fragility, configurational entropy and the potential energy landscape of glass forming liquids
Glass is a microscopically disordered, solid form of matter that results when a fluid is cooled or compressed in such a fashion that it does not crystallise. Almost all types of materials are capable of glass formation -- polymers, metal alloys, and molten salts, to name a few. Given such diversity, organising principl...
0011317v2
2001-09-05
Niobium based intermetallics as a source of high-current/high-magnetic field superconductors
The article is focused on low temperature intermetallic A15 superconducting wires development for Nuclear Magnetic Resonance, NMR, and Nuclear Magnetic Imaging, MRI, magnets and also on cryogen-free magnets. There are many other applications which would benefit from new development such as future Large Hadron Collider ...
0109088v1
2001-10-09
Thermoelectric power of Cerium and Ytterbium intermetallics
Temperature dependence S(T) of the thermoelectric power of metallic systems with cerium and ytterbium ions exhibits some characteristic features, which can be used to classify these systems into distinct categories. The experimental data are explained by the Kondo scattering in the presence of the crystal field splitti...
0110179v1
2001-11-06
Spin-dependent electrical transport in ion-beam sputter deposited Fe-Cr multilayers
The temperature dependence of the electrical resistivity and magnetoresistance of Xe-ion beam sputtered Fe-Cr multilayers has been investigated. The electrical resistivity between 5 and 300 K in the fully ferromagnetic state, obtained by applying a field beyond the saturation field (H_sat) necessary for the antiferroma...
0111084v1
2002-01-28
Automating First-Principles Phase Diagram Calculations
Devising a computational tool that assesses the thermodynamic stability of materials is among the most important steps required to build a ``virtual laboratory'', where materials could be designed from first-principles without relying on experimental input. Although the formalism that allows the calculation of solid st...
0201511v2
2002-06-19
Atomic Transport in Dense, Multi-Component Metallic Liquids
Pd43Ni10Cu27P0 has been investigated in its equilibrium liquid state with incoherent, inelastic neutron scattering. As compared to simple liquids, liquid PdNiCuP is characterized by a dense packing with a packing fraction above 0.5. The intermediate scattering function exhibits a fast relaxation process that precedes s...
0206364v2
2002-08-22
A nonplanar Peierls-Nabarro model and its applications to dislocation cross-slip
A novel semidiscrete Peierls-Nabarro model is introduced which can be used to study dislocation spreading at more than one slip planes, such as dislocation cross-slip and junctions. The strength of the model, when combined with ab initio calculations for the energetics, is that it produces essentiallyan atomistic simul...
0208440v1
2002-09-19
Magnetic Interactions and Transport in (Ga,Cr)As
The magnetic, transport, and structural properties of (Ga,Cr)As are reported. Zincblende Ga$_{1-x}$Cr$_{x}$As was grown by low-temperature molecular beam epitaxy (MBE). At low concentrations, x$\sim$0.1, the materials exhibit unusual magnetic properties associated with the random magnetism of the alloy. At low temperat...
0209477v2
2002-09-26
Lattice dynamics and correlated atomic motion from the atomic pair distribution function
The mean-square relative displacements (MSRD) of atomic pair motions in crystals are studied as a function of pair distance and temperature using the atomic pair distribution function (PDF). The effects of the lattice vibrations on the PDF peak widths are modelled using both a multi-parameter Born von-Karman (BvK) forc...
0209603v1
2003-04-02
Magnetic ordering of Mn sublattice, dense Kondo lattice behavior of Ce in (RPd3)8Mn (R = La, Ce)
We have synthesized two new interstitial compounds (RPd3)8Mn (R = La and Ce). The Mn ions present in "dilute" concentration of just 3 molar percent form a sublattice with an unusually large Mn-Mn near neighbor distance of ~ 85 nm. While the existence of (RPd3)8M (where M is a p-block element) is already documented in t...
0304038v1
2003-04-18
Electronic States and Cyclotron Resonance in n-type InMnAs
We present a theory for electronic and magneto-optical properties of n-type In(1-x)Mn(x)As magnetic alloy semiconductors in a high magnetic field, B. We use an 8-band Pidgeon-Brown model generalized to include the wavevector (Kz) dependence of the electronic states as well as s-d and p-d exchange interactions with loca...
0304434v3
2003-06-17
An improved continuous compositional-spread technique based on pulsed-laser deposition and applicable to large substrate areas
A new method for continuous compositional-spread (CCS) thin-film fabrication based on pulsed-laser deposition (PLD) is introduced. This approach is based on a translation of the substrate heater and the synchronized firing of the excimer laser, with the deposition occurring through a slit-shaped aperture. Alloying is a...
0306452v1
2003-06-25
Low temperature magnetic phase diagram of the cubic non-Fermi liquid system CeIn_(3-x)Sn_x
In this paper we report a comprehensive study of the magnetic susceptibility (\chi), resistivity (\rho), and specific heat (C_P), down to 0.5 K of the cubic CeIn_(3-x)Sn_x alloy. The ground state of this system evolves from antiferromagnetic (AF) in CeIn_3(T_N=10.2 K) to intermediate-valent in CeSn_3, and represents th...
0306658v2
2003-07-09
Fermionic Ising glasses with BCS pairing interaction in the presence of a transverse field
In the present work we have analyzed a fermionic infinite-ranged Ising spin glass with a local BCS coupling in the presence of transverse field. This model has been obtained by tracing out the conduction electrons degrees of freedom in a superconducting alloy. The transverse field \Gamma is applied in the resulting eff...
0307210v1
2003-10-06
Linear morphological stability analysis of the solid-liquid interface in rapid solidification of a binary system
The interface stability against small perturbations of the planar solid-liquid interface is considered analytically in linear approximation. Following the analytical procedure of Trivedi and Kurz (Trivedi R, Kurz W. Acta Metall 1986;34:1663), which is advancing the original treatment of morphological stability by Mulli...
0310095v1
2003-11-02
Stripe phase: analytical results for weakly coupled repulsive Hubbard model
Motivated by the stripe developments in cuprates, we review some analytical results of our studies of the charge- and spin density modulations (CDW and SDW) in a weakly coupled one dimensional repulsive electron system on a lattice. It is shown that close to half filling, in the high temperature regime above the mean f...
0311019v1
2003-12-21
Sharp lines in the absorption edge of EuTe and Pb$_{0.1}$Eu$_{0.9}$Te in high magnetic fields
The optical absorption spectra in the region of the \fd transition energies of epitaxial layers of of EuTe and \PbEuTe, grown by molecular beam epitaxy, were studied using circularly polarized light, in the Faraday configuration. Under \sigmam polarization a sharp symmetric absorption line (full width at half-maximum 0...
0312557v4
2004-05-26
The Effects of Phase Separation in the Cuprate Superconductors
Phase separation has been observed by several different experiments and it is believed to be closely related with the physics of cuprates but its exactly role is not yet well known. We propose that the onset of pseudogap phenomenon or the upper pseudogap temperature $T^*$ has its origin in a spontaneous phase separatio...
0405612v2
2004-06-26
Microscopic View on Short-Range Wetting at the Free Surface of the Binary Metallic Liquid Gallium-Bismuth: An X-ray Reflectivity and Square Gradient Theory Study
We present an x-ray reflectivity study of wetting at the free surface of the binary liquid metal gallium-bismuth (Ga-Bi) in the region where the bulk phase separates into Bi-rich and Ga-rich liquid phases. The measurements reveal the evolution of the microscopic structure of wetting films of the Bi-rich, low-surface-te...
0406661v1
2004-10-18
Modeling and Simulation of Strained Heteroepitaxial Growth
We introduce an off-lattice model with continuous particle distances and pair-potential interactions which allows for the efficient simulation of strained heteroepitaxial growth by means of kinetic Monte Carlo (KMC) simulations. We discuss in detail the application of our model to the simulation of three important stra...
0410456v1
2004-10-19
The upper critical field of filamentary Nb3Sn conductors
We have examined the upper critical field of a large and representative set of present multi-filamentary Nb3Sn wires and one bulk sample over a temperature range from 1.4 K up to the zero field critical temperature. Since all present wires use a solid-state diffusion reaction to form the A15 layers, inhomogeneities wit...
0410463v2
2004-10-22
Monte Carlo simulation of equilibrium L1_0 ordering in FePt nanoparticles
First, second and third nearest neighbor mixing potentials for FePt alloys, were calculated from first principles using a Connolly-Williams approach. Using the mixing potentials obtained in this manner, the dependency of equilibrium L1_0 ordering on temperature was studied for bulk and for a spherical nanoparticle with...
0410590v1
2004-12-22
On the growth and form of spherulites
Many structural materials (metal alloys, polymers, minerals, etc.) are formed by quenching liquids into crystalline solids. This highly non-equilibrium process often leads to polycrystalline growth patterns that are broadly termed "spherulites" because of their large-scale average spherical shape. Despite the prevalenc...
0412630v1
2005-04-26
Role of C in MgC_xNi_3 investigated from first principles
The influence of vacancies in the $C$ sub-lattice of $MgCNi_{3}$, on its structural, electronic and magnetic properties are studied by means of the density-functional based Korringa-Kohn-Rostoker Green's function method formulated in the atomic sphere approximation. Disorder is taken into account by means of coherent-p...
0504659v2
2005-06-09
Pressure-induced valence change in the rare earth metals:The case of Praseodymium
The rare earth metal praseodymium (Pr) transforms from the d-fcc crystal structure (Pr-III) to {$\alpha$}-U one (Pr-IV) at 20 GPa with a large volume collapse (${\rm\Delta} V/V$ = 0.16), which is associated with the valence change of the Pr ion. The two 4{\it f} electrons in the Pr ion is supposed to be itinerant in th...
0506222v1
2005-11-03
Phase transitions in Ni2+xMn1-xGa with a high Ni excess
Ferromagnetic shape memory alloys Ni$_{2+x}$Mn$_{1-x}$Ga were studied in the range of compositions $0.16 \le x \le 0.36$. Experimental phase diagram, constructed from differential scanning calorimetry, transport and magnetic measurements, exhibits distinctive feature in a compositional interval $0.18 \le x \le 0.27$, w...
0511086v2
2005-12-08
Statistical Theory of Spin Relaxation and Diffusion in Solids
A comprehensive theoretical description is given for the spin relaxation and diffusion in solids. The formulation is made in a general statistical-mechanical way. The method of the nonequilibrium statistical operator (NSO) developed by D. N. Zubarev is employed to analyze a relaxation dynamics of a spin subsystem. Pert...
0512182v2
2005-12-16
A Magnetic and Moessbauer Spectral Study of Core/Shell Structured Fe/Au Nanoparticles
Fe/Au nanoparticles have been chemically synthesized through a reverse micelle reaction and investigated by both conventional and synchrotron based x-ray diffraction and by magnetic and Moessbauer spectral studies. The powder x-ray diffraction patterns reveal both the presence of crystalline alpha-iron and gold and the...
0512413v1
2005-12-29
Anomalous precursor diamagnetism at low reduced magnetic fields and the role of Tc inhomogeneities in the superconductors Pb55In45 and underdoped La1.9Sr0.1CuO4
The magnetic field dependence of the magnetization was measured above the superconducting transition in a high-Tc underdoped cuprate La1.9Sr0.1CuO4 and in a low-Tc alloy (Pb55In45). Near the superconducting transition [typically for (T-Tc)/Tc<0.05] and under low applied magnetic field amplitudes [typically for H/Hc2(0)...
0512700v2
2006-01-05
Two-dimensional scaling properties of experimental fracture surfaces
The morphology of fracture surfaces encodes the various complex damage and fracture processes occurring at the microstructure scale that have lead to the failure of a given heterogeneous material. Understanding how to decipher this morphology is therefore of fundamental interest. This has been extensively investigated ...
0601087v1
2006-01-23
Dielectric Properties of Noncrystalline HfSiON
The dielectric properties of noncrystalline hafnium silicon oxynitride (HfSiON) films with a variety of atomic compositions were investigated. The films were deposited by reactive sputtering of Hf and Si in an O, N, and Ar mixture ambient. The bonding states, band-gap energies, atomic compositions, and crystallinities ...
0601503v1
2006-04-25
Thermopower of CexR1-xB6 (R=La, Pr and Nd)
The thermopower, S, of CexR1-xB6 (R=La, Pr, Nd) was investigated. S with a positive sign shows a typical behavior observed in the Ce Kondo system, an increase with decreasing temperature at high temperatures and a maximum at low temperatures. The S values of all the systems at high temperatures are roughly linearly dep...
0604582v1
2006-06-07
Ab initio study of the atomic motion in liquid metal surfaces: comparison with Lennard-Jones systems
It is established that liquid metals exhibit surface layering at the liquid-vapor interface, while dielectric simple systems, like those interacting through Lennard-Jones potentials, show a monotonic decay from the liquid density to that of the vapor. First principles molecular dynamics simulations of the liquid-vapor ...
0606186v1
2006-06-28
The random-anisotropy model in the strong-anisotropy limit
We investigate the nature of the critical behaviour of the random-anisotropy Heisenberg model (RAM), which describes a magnetic system with random uniaxial single-site anisotropy, such as some amorphous alloys of rare earths and transition metals. In particular, we consider the strong-anisotropy limit (SRAM), in which ...
0606728v1
2006-08-02
Magnetocatalytic Adiabatic Spin Torque Orbital Transformations for Novel Chemical and Catalytic Reaction Dynamics: The Little Effect
In this manuscript the theory and phenomena associated with the Little Effect are introduced as the spin induced orbital dynamics of confined fermions under strong magnetic and thermal environments. This Little Effect is considered in details for the electron transfer reactions associated with redox processes of Cu-Ag ...
0608071v1
2006-11-14
Topological Insulators with Inversion Symmetry
Topological insulators are materials with a bulk excitation gap generated by the spin orbit interaction, and which are different from conventional insulators. This distinction is characterized by Z_2 topological invariants, which characterize the groundstate. In two dimensions there is a single Z_2 invariant which dist...
0611341v2
2006-12-24
Carrier induced ferromagnetism in diluted local-moment systems
The electronic and magnetic properties of concentrated and diluted ferromagnetic semiconductors are investigated by using the Kondo lattice model, which describes an interband exchange coupling between itinerant conduction electrons and localized magnetic moments. In our calculations, the electronic problem and the loc...
0612611v1
2007-03-12
Molecular Dynamics Simulation of Ga Penetration along Sigma 5 Symmetric Tilt Grain Boundaries in an Al Bicrystal
Liquid metal embrittlement (LME) is a common feature of systems in which a low melting point liquid metal is in contact with another, higher melting point, polycrystalline metal. While different systems exhibit different LME fracture characteristics, the penetration of nanometer-thick liquid metal films along the grain...
0703307v1
2007-03-20
Investigation of the chemical vicinity of crystal defects in ion-irradiated Mg and AZ31 with coincident Doppler broadening spectroscopy
Crystal defects in magnesium and magnesium based alloys like AZ31 are of major importance for the understanding of their macroscopic properties. We have investigated defects and their chemical surrounding in Mg and AZ31 on an atomic scale with Doppler broadening spectroscopy of the positron annihilation radiation. In t...
0703524v3
2005-05-02
Particle acoustic detection in gravitational wave aluminum resonant antennas
The results on cosmic rays detected by the gravitational antenna NAUTILUS have motivated an experiment (RAP) based on a suspended cylindrical bar, which is made of the same aluminum alloy as NAUTILUS and is exposed to a high energy electron beam. Mechanical vibrations originate from the local thermal expansion caused b...
0505009v1
2001-05-30
The absolute continuity of the integrated density of states for magnetic Schrödinger operators with certain unbounded random potentials
The object of the present study is the integrated density of states of a quantum particle in multi-dimensional Euclidean space which is characterized by a Schr{\"o}dinger operator with magnetic field and a random potential which may be unbounded from above and below. In case that the magnetic field is constant and the ...
0105046v2
1998-09-24
Oxygen in the Earth's core: a first principles study
First principles electronic structure calculations based on density functional theory have been used to study the thermodynamic, structural and transport properties of solid solutions and liquid alloys of iron and oxygen at Earth's core conditions. Aims of the work are to determine the oxygen concentration needed to ac...
9809036v1
1999-01-26
Vibrating Wire for Beam Profile Scanning
The method for measurement of transverse profile (emittance) of the bunch by detecting of radiation arising scattering at of the bunch on the scanning wire is wide-spread. In this work the information about scattering bunch is proposed to measure using the oscillation frequency of the tightened scanning wire. In such w...
9901046v1
2001-08-12
DMSO-Induced Dehydration of DPPC Membranes Studied by X-ray Diffraction, Small-Angle Neutron Scattering, and Calorimetry
The influence of dimethyl sulfoxide (DMSO) on membrane thickness, multilamellar repeat distance, and phase transitions of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) was investigated by X-ray diffraction and small-angle neutron scattering (SANS). The differential scanning calorimetry (DSC) study of water fr...
0108019v1
2002-07-30
Work functions, ionization potentials, and in-between: Scaling relations based on the image charge model
We revisit a model in which the ionization energy of a metal particle is associated with the work done by the image charge force in moving the electron from infinity to a small cut-off distance just outside the surface. We show that this model can be compactly, and productively, employed to study the size dependence of...
0207116v2
2006-08-02
Infrared Absorption Investigations Confirm the Extraterrestrial Origin of Carbonado-Diamonds
The first complete infrared FTIR absorption spectra for carbonado-diamond confirm the interstellar origin for the most enigmatic diamonds known as carbonado. All previous attempts failed to measure the absorption of carbonado-diamond in the most important IR-range of 1000-1300 cm-1 (10.00-7.69 micro-m.) because of sili...
0608014v2
2007-01-24
Icosahedral quasicrystals for visible wavelengths by optical interference holography
Quasicrystals, realized in metal alloys, are a class of lattices exhibiting symmetries that fall outside the usual classification for periodic crystals. They do not have translational symmetry and yet the lattice points are well ordered. Furthermore, they exhibit higher rotational symmetry than periodic crystals. Becau...
0701276v1
1995-06-22
The Flux-Line Lattice in Superconductors
Magnetic flux can penetrate a type-II superconductor in form of Abrikosov vortices. These tend to arrange in a triangular flux-line lattice (FLL) which is more or less perturbed by material inhomogeneities that pin the flux lines, and in high-$T_c$ supercon- ductors (HTSC's) also by thermal fluctuations. Many propertie...
9506003v1
2007-05-28
Muon spin relaxation and hyperfine-enhanced 141Pr nuclear spin dynamic in Pr(Os,Ru)4Sb12 and (Pr,La)Os4Sb12
Zero- and longitudinal-field muon spin relaxation (MuSR) experiments have been carried out in the alloy series Pr(Os1-xRux)4Sb12 and Pr1-yLayOs4Sb12 to elucidate the anomalous dynamic muon spin relaxation observed in these materials. The damping rate associated with this relaxation varies with temperature, applied magn...
0705.4087v1
2007-07-19
Diffusive and ballistic current spin-polarization in magnetron-sputtered L1o-ordered epitaxial FePt
We report on the structural, magnetic, and electron transport properties of a L1o-ordered epitaxial iron-platinum alloy layer fabricated by magnetron-sputtering on a MgO(001) substrate. The film studied displayed a long range chemical order parameter of S~0.90, and hence has a very strong perpendicular magnetic anisotr...
0707.2943v1
2007-10-18
Effects of a tungsten addition on the morphological evolution, spatial correlations, and temporal evolution of a model Ni-Al-Cr superalloy
The effect of adding 2 at.% W to a model Ni-Al-Cr superalloy on the morphological evolution, spatial correlations and temporal evolution of g'(L12)-precipitates at 1073 K is studied with scanning electron microscopy and atomic force microscopy. Adding W yields a larger microhardness, earlier onset of spheroidal-to-cubo...
0710.3610v1
2007-10-22
Experimental and First principle calculation of Co_xNi_{(1-x)}Si solid solution structural stability
We report the investigation of the structural stability of Co$_{(1-x)}$Ni$_x$Si monosilicides for $0<x<1$. As CoSi crystallizes in the FeSi-type structure (B20) and NiSi is stable in the MnP-type structure (B31), a complete set of samples has been synthesized and a systematic study of phase formation under different an...
0710.4012v1
2007-11-21
Au-SN Flip-Chip Solder Bump for Microelectronic and Optoelectronic Applications
As an alternative to the time-consuming solder pre-forms and pastes currently used, a co-electroplating method of eutectic Au-Sn alloy was used in this study. Using a co-electroplating process, it was possible to plate the Au-Sn solder directly onto a wafer at or near the eutectic composition from a single solution. Tw...
0711.3323v1
2007-12-12
Nanoscale grains, high irreversibility field, and large critical current density as a function of high energy ball milling time in C-doped magnesium diboride
Magnesium diboride (MgB2) powder was mechanically alloyed by high energy ball milling with C to a composition of Mg(B0.95C0.05)2 and then sintered at 1000 C in a hot isostatic press. Milling times varied from 1 minute to 3000 minutes. Full C incorporation required only 30-60 min of milling. Grain size of sintered sampl...
0712.2056v1
2008-01-14
Hydrogen Dissociation and Diffusion on Ni and Ti -doped Mg(0001) Surfaces
It is well known, both theoretically and experimentally, that alloying MgH$_2$ with transition elements can significantly improve the thermodynamic and kinetic properties for H$_2$ desorption, as well as the H$_2$ intake by Mg bulk. Here we present a density functional theory investigation of hydrogen dissociation and ...
0801.2107v1
2008-01-15
Half-Metallic L2$_1$ Structures with (001) Planar Insertions
A number of L2$_1$ phase alloys (composition X$_2$YZ) are half-metallic. Although this structure is typically described in terms of an fcc Bravais lattice with a 4 atom basis, it can be viewed more simply as a variant of bcc or B2 in which planes of X$_2$ alternate with planes of YZ along the 001 direction. Using ab-in...
0801.2363v1
2008-02-04
Self-organized transient facilitated atomic transport in Pt/Al(111)
During the course of atomic transport in a host material, impurity atoms need to surmount an energy barrier driven by thermodynamic bias or at ultra-low temperatures by quantum tunneling. In the present article we demonstrate using atomistic simulations that at ultra-low temperature transient inter-layer atomic transpo...
0802.0347v1
2008-06-27
Defect-induced incompatibility of elastic strains: dislocations within the Landau theory of martensitic phase transformations
In dislocation-free martensites the components of the elastic strain tensor are constrained by the Saint-Venant compatibility condition which guarantees continuity of the body during external loading. However, in dislocated materials the plastic part of the distortion tensor introduces a displacement mismatch that is r...
0806.4564v2
2008-07-15
Superconductivity in the PbO-type Structure alpha-FeSe
The recent discovery of superconductivity with relatively high transition temperature Tc in the layered iron-based quaternary oxypnictides La[ O1-xFx] FeAs was a real surprise. The excitement generated can be seen by the number of subsequent works published within a very short period of time. Although there exists supe...
0807.2369v2
2008-08-20
Crystal Growth and Anisotropic Magnetic Properties of RAg$_2$Ge$_2$ (R = Pr, Nd and Sm) Single Crystals
We report the single crystal growth and anisotropic magnetic properties of the tetragonal RAg$_2$Ge$_2$ (R = Pr, Nd and Sm) compounds which crystallize in the ThCr$_2$Si$_2$ type crystal structure with the space group \textit{I4/mmm}. The single crystals of RAg$_2$Ge$_2$ (R = Pr, Nd and Sm) were grown by self-flux meth...
0808.2826v1
2008-09-09
Intermediate Phases, structural variance and network demixing in chalcogenides: the unusual case of group V sulfides
We review Intermediate Phases (IPs) in chalcogenide glasses and provide a structural interpretation of these phases. In binary group IV selenides, IPs reside in the 2.40 < r < 2.54 range, and in binary group V selenides they shift to a lower r, in the 2.29< r < 2.40 range. Here r represents the mean coordination number...
0809.1469v2
2008-11-03
Compensation-dependent in-plane magnetization reversal processes in Ga1-xMnxP1-ySy
We report the effect of dilute alloying of the anion sublattice with S on the in-plane uniaxial magnetic anisotropy and magnetization reversal process in Ga1-xMnxP as measured by both ferromagnetic resonance (FMR) and superconducting quantum interference device (SQUID) magnetometry. At T=5K, raising the S concentration...
0811.0385v1
2008-11-27
Anomalous binding of Fe atoms in chromium
Binding of 57Fe atoms in a metallic chromium was investigated in a Cr-Fe alloy, containing less than 0.1 at% Fe enriched to ~95 % in 57Fe isotope, using 57Fe-site Mossbauer spectroscopy. The binding force was derived from the Debye temperature, T_D, that, in turn, was calculated from the temperature dependence of the c...
0811.4533v1
2009-03-02
Ferromagnetic properties of p-(Cd,Mn)Te quantum wells: Interpretation of magneto-optical measurements by Monte Carlo simulations
In order to single out dominant phenomena that account for carrier-controlled magnetism in p-(Cd,Mn)Te quantum wells we have carried out magneto-optical measurements and Monte Carlo simulations of time dependent magnetization. The experimental results show that magnetization relaxation is faster than 20 ns in the param...
0903.0406v1
2009-06-29
A novel wear-resistant magnetic thin film material based on a $Ti_{1-x}Fe_xC_{1-y}$ nanocomposite alloy
In this study we report on the film growth and characterization of thin (approximately 50 nm thick) Ti-Fe-C films deposited on amorphous quartz. The experimental studies have been complemented by first principles density functional theory (DFT) calculations. Upon annealing of as-prepared films, the composition of the m...
0906.5386v1
2009-08-09
Topological Surface States Protected From Backscattering by Chiral Spin Texture
Topological insulators are a new class of insulators in which a bulk gap for electronic excitations is generated by strong spin orbit coupling. These novel materials are distinguished from ordinary insulators by the presence of gapless metallic boundary states, akin to the chiral edge modes in quantum Hall systems, but...
0908.1247v1
2009-08-12
High sensitivity of 17O NMR to p-d hybridization in transition metal perovskites: first principles calculations of large anisotropic chemical shielding
A first principles embedded cluster approach is used to calculate O chemical shielding tensors, sigma, in prototypical transition metal oxide ABO_3 perovskite crystals. Our principal findings are 1) a large anisotropy of sigma between deshielded sigma_x ~ sigma_y and shielded sigma_z components (z along the Ti-O bond);...
0908.1779v2
2009-08-13
Role of thermal vibrations in phase transitions
All theoretical models (Heisenberg, Ising etc.) assume a negligible role for thermal vibrations in alloy and magnetic phase transitions. Analysis of diffraction data conclusively proves that this assumption is incorrect. A simple criterion emerges that theoretical models can ignore the role of thermal vibrations only i...
0908.1873v2
2009-09-13
Unconventional ferromagnetism and transport properties of (In,Mn)Sb dilute magnetic semiconductor
Narrow-gap higher mobility semiconducting alloys In_{1-x}Mn_{x}Sb were synthesized in polycrystalline form and their magnetic and transport properties have been investigated. Ferromagnetic response in In_{0.98}Mn_{0.02}Sb was detected by the observation of clear hysteresis loops up to room temperature in direct magneti...
0909.2407v2
2009-09-16
Experimental Evaluation of the Rheological Properties of Veriflex Shape Memory Polymer
Shape memory polymers (SMPs) are materials with a great potential for future use in smart materials and structures. When heated from cold state (below the transformation temperature, which can either be the glass transition temperature or the melting temperature of the polymer) to hot state (above the transformation te...
0909.2953v1
2009-10-09
Space efficient opposed-anvil high-pressure cell and its application to optical and NMR measurements up to 9 GPa
We have developed a new type of opposed-anvil high pressure cell with substantially improved space efficiency. The clamp cell and the gasket are made of non-magnetic Ni-Cr-Al alloy. Non-magnetic tungsten carbide (NMWC) is used for the anvils. The assembled cell with the dimension \phi 29mm \times 41mm is capable of gen...
0910.1767v2
2009-10-23
Supression of electron correlations in the superconducting alloys of Rh$_{17-x}$Ir$_x$S$_{15}$
We have studied the effect of Iridium doping (Rh$_{17-x}$Ir$_{x}$S$_{15}$) in the Rhodium sites of the strongly correlated superconductor Rh$_{17}$S$_{15}$. Even at low levels of doping (x = 1 and 2) we see a drastic change in the superconducting properties as compared to those of the undoped system. We deduce that the...
0910.4478v2