publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2002-10-25 | Anisotropic and incommensurate spin fluctuations in hcp iron and some other nearly magnetic metals | We present an ab initio theoretical formalism for the static paramagnetic
spin susceptibility of metals at finite temperatures. Since relativistic
effects, e.g. spin-orbit coupling, are included, we can identify the anisotropy
or easy axes of the spin fluctuations. Our calculations find hcp-iron to be
unstable to in ab... | 0210581v1 |
2002-11-15 | The Korringa-Kohn-Rostoker Non-Local Coherent Potential Approximation (KKR-NLCPA) | We introduce the Korringa-Kohn-Rostocker non-local coherent potential
approximation (KKR-NLCPA) for describing the electronic structure of disordered
systems. The KKR-NLCPA systematically provides a hierarchy of improvements upon
the widely used KKR-CPA approach and includes non-local correlations in the
disorder confi... | 0211328v2 |
2002-12-04 | Chemical localization | Analysis of experimental data shows that the metal--insulator transition is
possible in materials composed of atoms of only metallic elements. Such a
transition may occur in spite of the high concentration of valence electrons.
It requires stable atomic configurations to act as deep potential traps
absorbing dozens of ... | 0212097v1 |
2002-12-18 | Synthesis, characterization and modeling of high quality ferromagnetic Cr-doped AlN thin films | We report a theoretical and experimental investigation of Cr-doped AlN.
Density functional calculations predict that the isolated Cr t2 defect level in
AlN is 1/3 full, falls approximately at midgap, and broadens into an impurity
band for concentrations over 5%. Substitutional Al1-xCrxN random alloys with
0.05 <= x <= ... | 0212459v1 |
2003-01-20 | Modeling Melting in Binary Systems | A coarsened model for a binary system with limited miscibility of components
is proposed; the system is described in terms of structural states in small
parts of the material. The material is assumed to have two alternative types of
crystalline local arrangements associated with two components of the alloy.
Fluctuating... | 0301342v1 |
2003-01-21 | Kinetic Theory of the Overlapping Phase Transformations | Often a number of precipitation processes in steels and alloys occur
simultaneously (they have the same origin in time) albeit at different rates.
Consequently, isothermic transformations are accompanied, in this case, by the
occurrence of second processes of precipitation that influence the changes of
the macroscopic ... | 0301391v1 |
2003-02-07 | Phase-field study for the splitting mechanism of coherent misfitting precipitates in anisotropic elastic media | Coherent misfitting precipitates in elastically stressed media such as
$\gamma \prime$ particles in nickel-based super-alloys show various splitting
patterns such as doublets, quartets, or octets due to their misfit strain
energy. While it is an interesting instability phenomenon defying conventional
surface thermodyna... | 0302139v1 |
2003-02-13 | Does the thermal spike affect low-energy ion-induced interfacial mixing? | Molecular dynamics simulations have been used to obtain the three-dimensional
distribution of interfacial mixing and cascade defects in Ti/Pt multilayer
system due to single 1 keV $Ar^+$ impacts at grazing angle of incidence. The
Ti/Pt system was chosen because of its relatively high heat of mixing in the
binary alloy ... | 0302262v3 |
2003-02-22 | Huge enhancement of electronmechanical responses in compositionally modulated PZT | Monte Carlo simulations based on a first-principles-derived Hamiltonian are
conducted to study the properties of PZT alloys compositionally modulated along
the [100] pseudocubic direction near the morphotropic phase boundary (MPB). It
is shown that compositional modulation causes the polarization to continuously
rotate... | 0302462v2 |
2003-03-11 | The magnetic field influence on magnetostructural phase transition in Ni2.19Mn0.81Ga | Magnetic properties of a polycrystalline alloy Ni$_{2.19}$Mn$_{0.81}$Ga,
which undergoes a first-order magnetostructural phase transition from cubic
paramagnetic to tetragonal ferromagnetic phase, are studied. Hysteretic
behavior of isothermal magnetization $M(H)$ has been observed in a temperature
interval of the magn... | 0303187v1 |
2003-03-11 | In(1-x)Mn(x)Sb - a new narrow gap ferromagnetic semiconductor | A narrow-gap ferromagnetic In(1-x)Mn(x)Sb semiconductor alloy was
successfully grown by low-temperature molecular beam epitaxy on CdTe/GaAs
hybrid substrates. Ferromagnetic order in In(1-x)Mn(x)Sb was unambiguously
established by the observation of clear hysteresis loops both in direct
magnetization measurements and in... | 0303212v1 |
2003-03-18 | Properties and Curie Temperature (130 K) of Heavily Mn-doped Quaternary Alloy Ferromagnetic Semiconductor (InGaMn)As Grown on InP | We have studied magnetic properties of heavily Mn-doped
[(In0.44Ga0.56)0.79Mn0.21]As thin films grown by low-temperature molecular-beam
epitaxy (LT-MBE) on InP substrates. The (InGaMn)As with high Mn content (21%)
was obtained by decreasing the growth temperature to 190 degC. When the
thickness of the [(In0.44Ga0.56)0.... | 0303333v1 |
2003-03-26 | Frozen Quasi Long Range Order in Random Anisotropy Heisenberg Magnet | Extensive Monte Carlo simulations are used to investigate the low-temperature
properties of the random anisotropy Heisenberg model, which describes the
magnetic behavior of amorphous rare-earth-transition metal alloy. We show that
the low-temperature phase in weak-anisotropy region is characterized by a {\it
frozen-in}... | 0303552v4 |
2003-04-04 | The easy axis of the magnetic response of the conduction electrons of yttrium and rare earths | We describe a scheme for first-principles calculations of the static,
paramagnetic, spin susceptibility of metals with relativistic effects such as
spin-orbit coupling included. This gives the direction for an applied modulated
magnetic field to maximise its response. This easy axis depends on the
modulation's wave-vec... | 0304112v1 |
2003-04-10 | First Investiation of magnetic ground states in the rare-earth intermetallic compounds RAl$_{0.9}$Si$_{1.1}$ (R = Ce, Pr, Gd) | We report the magnetic properties strongly varying with the rare-earth
elements in the newly found ternary compounds $R$Al$_{0.9}$Si$_{1.1}$, which
crystallize in the tetragonal $\alpha$-ThSi$_2$-type structure. For $R$ = Ce
the alloy has a weak ferromagnetism below 11 K and for $R$ = Pr it orders
ferromagnetically at ... | 0304235v1 |
2003-04-11 | Spin Manipulation of Free 2-Dimensional Electrons in Si/SiGe Quantum Wells | An important requirement for a physical embodiment of a quantum computer is
that arbitrary single-qubit operations can be performed. In the case of
spin-qubits, this means that arbitrary spin rotations must be possible. Here we
demonstrate spin rotations of an ensemble of free 2-dimensional electrons
confined to a sili... | 0304284v1 |
2003-04-18 | Training of the Ni-Mn-Fe-Ga ferromagnetic shape-memory alloys by cycling in a high magnetic field | The temperature and magnetic field dependencies of Ni-Mn-Ga polycrystals
deformation are investigated. Ingots were prepared by arc-melting in argon
atmosphere and further annealing. A training procedure (cycling across the
martensitic transition point) for the two-way shape-memory effect was performed
with Ni$_{2.16}$F... | 0304425v1 |
2003-05-03 | Synthesis of Single Phase Hg-1223 High Tc Superconducting Films With Multistep Electrolytic Process | We report the multistep electrolytic process for the synthesis of high Tc
single phase HgBa2Ca2Cu3O8+ (Hg-1223) superconducting films. The
process includes : i) deposition of BaCaCu precursor alloy, ii) oxidation of
BaCaCu films, iii) electrolytic intercalation of Hg in precursor BaCaCuO films
and iv) electroch... | 0305059v1 |
2003-05-11 | Electron transport and energy relaxation in dilute magnetic alloys | We consider the effect of the RKKY interaction between magnetic impurities on
the electron relaxation rates in a normal metal. The interplay between the RKKY
interaction and the Kondo effect may result in a non-monotonic temperature
dependence of the electron momentum relaxation rate, which determines the Drude
conduct... | 0305240v1 |
2003-05-27 | Probing a ferromagnetic critical regime using nonlinear susceptibility | The second order para-ferromagnetic phase transition in a series of amorphous
alloys (Fe{_5}Co{_{50}}Ni{_{17-x}}Cr{_x}B{_{16}}Si{_{12}}) is investigated
using nonlinear susceptibility. A simple molecular field treatment for the
critical region shows that the third order suceptibility (chi{_3}) diverges on
both sides of... | 0305617v1 |
2003-07-18 | Structures and electromagnetic properties of the A-site ordered/disordered manganites; RBaMn2O6/R0.5Ba0.5MnO3 (R = Y and rare earth elements) | The discovery of novel structural and physical properties in the $A$-site
ordered manganite $R$BaMn$_2$O$_6$ ($R$ = Y and rare earth elements) has
demanded new comprehension about perovskite manganese oxides. In the present
study, the $A$-site disordered form $R$$_{0.5}$Ba$_{0.5}$MnO$_3$ was
successfully synthesized an... | 0307456v1 |
2003-07-18 | Phonon scattering in quasicrystalline i-Al_{72}Pd_{19.5}Mn_{8.5}: A study of the low-temperature thermal conductivity | We measured the thermal conductivity of an icosahedral quasicrystal
i-Al_{72}Pd_{19.5}Mn_{8.5} in the temperature range between 0.4 K and 300 K.
The analysis of the low-temperature results was based on a Debye-type model.
The results of the analysis for the two temperature regions of 0.4 K <T<40 K
and 0.4 K <T<1 K, are... | 0307458v2 |
2003-08-09 | Phase field modeling of electrochemistry II: Kinetics | The kinetic behavior of a phase field model of electrochemistry is explored
for advancing (electrodeposition) and receding (electrodissolution) conditions
in one dimension. We described the equilibrium behavior of this model in [J. E.
Guyer, W. J. Boettinger, J.A. Warren, and G. B. McFadden, ``Phase field
modeling of e... | 0308179v2 |
2003-08-14 | Nanoscale-SiC doping for enhancing Jc and Hc2 in the Superconducting MgB2 | The effect of nanoscale-SiC doping of MgB2 was investigated using transport
and magnetic measurements. It was found that there is a clear correlation
between the critical temperature Tc, the resistivity r, the residual
resistivity ratio, RRR = R(300K)/R(40K), the irreversibility field H* and the
alloying state in the s... | 0308265v1 |
2003-08-19 | Magnetization relaxation in (Ga,Mn)As ferromagnetic semiconductors | We describe a theory of Mn local-moment magnetization relaxation due to p-d
kinetic-exchange coupling with the itinerant-spin subsystem in the
ferromagnetic semiconductor (Ga,Mn)As alloy. The theoretical Gilbert damping
coefficient implied by this mechanism is calculated as a function of Mn moment
density, hole concent... | 0308386v3 |
2003-09-04 | Study of Crystal-field Effects in Rare-earth (RE) - Transition-metal Intermetallic Compounds and in RE-based Laser Crystals | Rare-earth (RE) based compounds and alloys are of great interest both for
their fundamental physical properties and for applications. In order to tailor
the required compounds for a specific task, one must be able to predict the
energy level structure and transition intensities for any magnetic ion in any
crystalline e... | 0309100v1 |
2003-09-06 | Impurities block the alpha to omega martensitic transformation in titanium | The onset and kinetics of martensitic transformations are controlled by
impurities trapped during the transformation. For the alpha to omega
transformation in Ti, ab initio methods yield the changes in both the relative
stability of and energy barrier between the phases. Using the recently
discovered transformation pat... | 0309162v1 |
2003-09-10 | Electron-Polarization Coupling in Superconductor-Ferroelectric Superlattices | We present a phenomenological model of periodic ferroelectric-superconductor
(FE-S) heterostructures containing two alternating ferroelectric and
superconducting layers. The interaction at the FE-S contacts is described as a
coupling of the local carrier density of the superconductor with the
spontaneous ferroelectric ... | 0309250v2 |
2003-09-12 | Proximity and Josephson effects in superconductor - antiferromagnetic Nb / γ-Fe50Mn50 heterostructures | We study the proximity effect in superconductor (S), antiferromagnetic (AF)
bilayers, and report the fabrication and measurement of the first trilayer
S/AF/S Josephson junctions. The disordered f.c.c. alloy \gamma-Fe50Mn50 was
used as the AF, and the S is Nb. Micron and sub-micron scale junctions were
measured, and the... | 0309313v1 |
2003-09-20 | Diluted II-VI Oxide Semiconductors with Multiple Band Gaps | We report the realization of a new multi-band-gap semiconductor. The highly
mismatched alloy Zn1-yMnyOxTe1-x has been synthesized using the combination of
oxygen ion implantation and pulsed laser melting. Incorporation of small
quantities of isovalent oxygen leads to the formation of a narrow,
oxygen-derived band of ex... | 0309477v1 |
2003-10-14 | The Elusive Bose Metal | The conventional theory of metals is in crisis. In the last 15 years, there
has been an unexpected sprouting of metallic states in low dimensional systems
directly contradicting conventional wisdom. For example, bosons are thought to
exist in one of two ground states: condensed in a superconductor or localized
in an in... | 0310316v1 |
2003-10-17 | A Hybrid Al(0.10)Ga(0.90)As/AlAs Bilayer Electron System | We have fabricated a device composed of two closely coupled two-dimensional
electron systems, one of which resides within an AlAs quantum well (QW) at the
X point of the Brillouin zone (BZ), while the other is contained at the
$\Gamma$ point of the BZ in the alloy Al_{0.10}Ga_{0.90}As, grown directly
below the AlAs QW.... | 0310434v2 |
2003-10-25 | Temperature dependence of the coercive field in single-domain particle systems | The magnetic properties of Cu97Co3 and Cu90Co10 granular alloys were measured
over a wide temperature range (2 to 300K). The measurements show an unusual
temperature dependence of the coercive field. A generalized model is proposed
and explains well the experimental behavior over a wide temperature range. The
coexisten... | 0310604v2 |
2003-10-31 | A possible route to grow a (Mn:Si(1-x)Gex)-based diluted magnetic semiconductor | We systematically investigate, using ab initio density-functional theory
calculations, the properties of interstitial and substitutional Mn in both Si
and Ge, as well as in the Si(1-x)Gex alloy. We show that volume effects are not
the main reason Mn prefers to be a subsitutional impurity in pure Ge, and
chemical effect... | 0310770v1 |
2003-12-05 | On the fluctuations of jamming coverage upon random sequential adsorption on homogeneous and heterogeneous media | The fluctuations of the jamming coverage upon Random Sequential Adsorption
(RSA) are studied using both analytical and numerical techniques. Our main
result shows that these fluctuations (characterized by $\sigma_{\theta_J}$)
decay with the lattice size according to the power-law $\sigma_{\theta_J}
\propto L^{-1/ \nu}$... | 0312171v1 |
2003-12-18 | Reversibility Window, Aging, and Nanoscale Phase Separation in GexAsxS1-2x Bulk Alloy Glasses | The non-reversing enthalpy near Tg, DHnr, in bulk GexAsxS1-2x glasses is
found to display a global minimum (~0) in the 0.11 < x < 0.15 range, the
reversibility window. Furthermore, the DHnr term is found to age for glass
compositions both below (x < 0.11) and above (x > 0.15) the window but not in
the window. Glass com... | 0312481v1 |
2004-01-22 | Suppression of superconductivity by non-magnetic disorder in the organic superconductor (TMTSF)2(ClO4)(1-x)(ReO4)x | We present a study of the superconducting properties (Tc and Hc2) in the
solid solution (TMTSF)2(ClO4)(1-x)(ReO4)x with a ReO-4 nominal concentration up
to x = 6%. The dramatic suppression of Tc when the residual resistivity is
increased upon alloying with no modification of the Fermi surface is the
signature of non-co... | 0401420v3 |
2004-01-28 | Importance of Thermal Disorder on the Properties of Alloys: Origin of Paramagnetism and Structural Anomalies in Iron-Aluminum | The bcc-based Fe_{1-x}Al_{x} exhibit interesting magnetic and anomalous
structural properties as a function of composition and sample processing
conditions arising from thermal or off-stoichiometric chemical disorder, and,
although well studied, these properties are not understood. In stoichiometric
B2 FeAl, including ... | 0401587v1 |
2004-01-30 | Magnetoelectric Effects in Ferromagnetic Metal-Piezoelectric Oxide Layered Structures | Frequency dependence of magnetoelectric (ME) coupling is investigated in
trilayers of ferromagnetic alloy and piezoelectric lead zirconate titanate
(PZT). The ferromagnetic phases studied include permendur, a soft magnet with
high magnetostriction, iron, nickel, and cobalt. Low frequency data on ME
voltage coefficient ... | 0401648v1 |
2004-02-24 | A Collective Heavy Fermion State and Superconductivity in Pr$_{1-x}$La$_x$Os$_4$Sb$_{12}$: Specific Heat and Susceptibility Study | Low temperature susceptibility and specific heat for single crystals of
Pr$_{1-x}$La$_x$Os$_4$Sb$_{12}$ (0 $\leq x$ $\leq 1$) are reported. La-doping
leaves CEF energies of Pr essentially unchanged. The average $T_c$ is only
weakly affected by the La-substitution and varies approximately linearly
between the end-compou... | 0402599v1 |
2004-04-06 | Disorder, inhomogeneity and spin dynamics in f-electron non-Fermi liquid systems | Muon spin rotation and relaxation ($\mu$SR) experiments have yielded evidence
that structural disorder is an important factor in many f-electron-based
non-Fermi-liquid (NFL) systems. Disorder-driven mechanisms for NFL behaviour
are suggested by the observed broad and strongly temperature-dependent $\mu$SR
(and NMR) lin... | 0404118v1 |
2004-04-27 | High Field ESR Study of the pi-d Correlated Organic Conductor lambda-(BETS)2Fe0.6Ga0.4Cl4 | Submillimeter and millimeter wave electron spin resonance (ESR) measurements
of the pi-d correlated organic conductor lambda-(BETS)2Fe0.6Ga0.4Cl4 have been
performed. Antiferromagnetic resonance (AFMR) has been observed in the
insulating antiferromagnetic phase, and its frequency-field dependence can be
reproduced by t... | 0404645v1 |
2004-04-27 | Viscoelastic model for the dynamic structure of binary systems | This paper presents the viscoelastic model for the Ashcroft-Langreth dynamic
structure factors of liquid binary mixtures. We also provide expressions for
the Bhatia-Thornton dynamic structure factors and, within these expressions,
show how the model reproduces both the dynamic and the self-dynamic structure
factors cor... | 0404649v1 |
2004-04-30 | The origin of the E+ transition in GaAsN alloys | Optical properties of GaAsN system with nitrogen concentrations in the range
of 0.9-3.7% are studied by full-potential LAPW method in a supercell approach.
The E+ transition is identified by calculating the imaginary part of the
dielectric function. The evolution of the energy of this transition with
nitrogen concentra... | 0405004v1 |
2004-05-18 | Genetic Programming for Multi-Timescale Modeling | A bottleneck for multi-timescale dynamics is the computation of the potential
energy surface (PES). We explore the use of genetic programming (GP) to
symbolically regress a mapping of the saddle-point barriers from only a few
calculated points via molecular dynamics, thereby avoiding explicit calculation
of all the bar... | 0405415v1 |
2004-05-24 | Enhancement of Critical Current Density in low level Al-doped MgB2 | Two sets of MgB2 samples doped with up to 5 at. % of Al were prepared in
different laboratories using different procedures. Decreases in the a and c
lattice parameters were observed with Al doping confirming Al substitution onto
the Mg site. The critical temperature (Tc) remained largely unchanged with Al
doping. For 1... | 0405567v1 |
2004-06-02 | Suppression of the $γ-α$ structural phase transition in $Ce_{0.8} La_{0.1} Th_{0.1}$ by large magnetic fields | The $\gamma-\alpha$ transition in Ce$_{0.8}$La$_{0.1}$Th$_{0.1}$ is measured
as a function of applied magnetic field using both resistivity and
magnetization. The $\gamma - \alpha$ transition temperature decreases with
increasing magnetic field, reaching zero temperature at around 56 T. The
magnetic-field dependence of... | 0406043v1 |
2004-06-10 | Andreev reflection observation in Nb/FeSi/Nb and Nb/FeSi/Si/Nb Josephson junctions | Electrical properties of Josephson junctions Nb/FeSi/Nb with
superconductor/ferromagnet (S/F)interfaces are presented. Due to Andreev
reflection the nearly exact quadruple enhancement of the tunnel junction
differential conductance compared with that of the normal state was achieved.
The transparency of the S/F interfa... | 0406242v1 |
2004-06-11 | sin(2 phi) current-phase relation in SFS junctions with decoherence in the ferromagnet | We propose a theoretical description of the sin(2 phi) current-phase relation
in SFS junctions at the 0-$\pi$ cross-over obtained in recent experiments by
Sellier et al. [Phys. Rev. Lett. 92, 257005 (2004)] where it was suggested that
a strong decoherence in the magnetic alloy can explain the magnitude of the
residual ... | 0406275v2 |
2004-06-22 | Self-interaction correction in multiple scattering theory | We propose a simplified version of self-interaction corrected local
spin-density (SIC-LSD) approximation, based on multiple scattering theory,
which implements self-interaction correction locally, within the KKR method.
The multiple scattering aspect of this new SIC-LSD method allows for the
description of crystal pote... | 0406515v3 |
2004-06-24 | Surface layering of liquids: The role of surface tension | Recent measurements show that the free surfaces of liquid metals and alloys
are always layered, regardless of composition and surface tension; a result
supported by three decades of simulations and theory. Recent theoretical work
claims, however, that at low enough temperatures the free surfaces of all
liquids should b... | 0406579v1 |
2004-06-30 | Spin Polarization and Electonic Structure of Room-Curie Ferromagnetic Mn5Ge3 Epilayers | Germanium-based alloys hold great promise for future spintronics
applications, due to their potential for integration with conventional Si-based
electronics. Mn5Ge3 exhibits strong ferromagnetism up to the Curie temperature
Tc~295K. We use Point Contact Andreev Reflection (PCAR) spectroscopy to measure
the spin polariz... | 0407001v1 |
2004-07-05 | Influence of Trapping on the Exciton Dynamics of Al_xGa_1-xAs Films | We present a systematic study on the exciton relaxation in high purity AlGaAs
epilayers. The time for the excitonic photoluminescence to reach its maximum
intensity (t_max) shows a non-monotonic dependence on excitation density which
is attributed to a competition between exciton localization and carrier-carrier
scatte... | 0407102v2 |
2004-07-13 | Experimental X-Ray Studies of Liquid Surfaces | Over the past two decades synchrotron facilities dedicated to the generation
of x-rays for study of atoms, molecules and condensed matter have proliferated
all over the world. As a result of the special properties of x-rays produced by
these machines, there has been an enormous growth in the experimental
possibilities.... | 0407333v2 |
2004-07-26 | Unusual structural tuning of magnetism in cuprate perovskites | Understanding the structural underpinnings of magnetism is of great
fundamental and practical interest. Se_{1-x}Te_{x}CuO_{3} alloys are model
systems for the study of this question, as composition-induced structural
changes control their magnetic interactions. Our work reveals that this
structural tuning is associated... | 0407677v1 |
2004-07-29 | Kondo Effect on Mesoscopic Scale (Review) | Following the discovery of the Kondo effect the bulk transport and magnetic
behavior of the dilute magnetic alloys have been successfully described. In the
last fifteen years new directions have been developed as the study of the
systems of reduced dimensions and the artificial atoms so called quantum dots.
In this rev... | 0407766v1 |
2004-08-12 | Electric field induced narrowing of exciton line width | Considering effects of electric field on the low temperature absorption line
of quantum well excitons, we show that, for moderate strength of the electric
field, the main contribution to the field dependence of the line-width results
from field induced modifications of inhomogeneous broadening of excitons. We
find that... | 0408296v2 |
2004-08-31 | On the role of electron correlation and disorder on persistent currents in isolated one-dimensional rings | To understand the role of electron correlation and disorder on persistent
currents in isolated 1D rings threaded by magnetic flux $\phi$, we study the
behavior of persistent currents in aperiodic and ordered binary alloy rings.
These systems may be regarded as disordered systems with well-defined
long-range order so th... | 0408671v2 |
2004-09-08 | Large tunneling anisotropic magnetoresistance in (Ga,Mn)As nanoconstrictions | We report a large tunneling anisotropic magnetoresistance (TAMR) in a thin
(Ga,Mn)As epilayer with lateral nanoconstrictions. The observation establishes
the generic nature of this effect, which originates from the spin-orbit
coupling in a ferromagnet and is not specific to a particular tunnel device
design. The latera... | 0409209v1 |
2004-09-17 | Photoluminescence pressure coefficients of InAs/GaAs quantum dots | We have investigated the band-gap pressure coefficients of self-assembled
InAs/GaAs quantum dots by calculating 17 systems with different quantum dot
shape, size, and alloying profile using atomistic empirical pseudopotential
method within the ``strained linear combination of bulk bands'' approach. Our
results confirm ... | 0409442v1 |
2004-09-23 | Crack (Non)Propagation in Amorphous Media | We study Mode I crack propagation in amorphous material via a molecular
dynamics simulation of a binary alloy with pairwise central-force interactions.
We find that when the system is subjected to constant displacement after
introduction of a seed crack, the crack does not propagate. This was found to
be true both for ... | 0409607v1 |
2004-10-06 | Sheared Solid Materials | We present a time-dependent Ginzburg-Landau model of nonlinear elasticity in
solid materials. We assume that the elastic energy density is a periodic
function of the shear and tetragonal strains owing to the underlying lattice
structure. With this new ingredient, solving the equations yields formation of
dislocation di... | 0410151v1 |
2004-10-06 | Magnetovolume instabilities in the pressure dependence of the K-edge circular dichroism of Fe3C Invar particles | The p-electrons of carbon in the interstitial compound Fe3C hybridize with
the Fe d-band and enhance the valence electron concentration of Fe from 8 to
8.67. At this concentration, substitutional 3d transition metals and alloys
exhibit strong moment-volume coupling phenomena and associated magnetovolume
instabilities, ... | 0410156v1 |
2004-10-20 | Local environment of Nitrogen in GaN{y}As{1-y} epilayers on GaAs (001) studied using X-ray absorption near edge spectroscopy | X-ray absorption near-edge spectroscopy (XANES) is used to study the N
environment in bulk GaN and in GaN{y}As{1-y} epilayers on GaAs (001), for y
\~5%. Density-functional optimized structures were used to predict XANES via
multiple-scattering theory. We obtain striking agreement for pure GaN. An alloy
model with nitro... | 0410514v1 |
2004-11-10 | Interplay of Strain Relaxation and Chemically Induced Diffusion Barriers: Nanostructure Formation in 2D Alloys | We study the formation of nanostructures with alternating stripes composed of
bulk-immiscible adsorbates during submonolayer heteroepitaxy. We evaluate the
influence of two mechanisms considered in the literature: (i) strain relaxation
by alternating arrangement of the adsorbate species, and (ii) kinetic
segregation du... | 0411271v1 |
2004-11-12 | Effects of short-range order on the electronic structure of disordered metallic systems | For many years the Korringa-Kohn-Rostoker coherent-potential approximation
(KKR-CPA) has been widely used to describe the electronic structure of
disordered systems based upon a first-principles description of the crystal
potential. However, as a single-site theory the KKR-CPA is unable to account
for important environ... | 0411347v2 |
2004-11-24 | Electrical Spin Injection in Multi-Wall carbon NanoTubes with transparent ferromagnetic contacts | We report on electrical spin injection measurements on MWNTs . We use a
ferromagnetic alloy Pd$_{1-x}$Ni$_{x}$ with x $\approx$ 0.7 which allows to
obtain devices with resistances as low as 5.6 $k\Omega$ at 300 $K$. The yield
of device resistances below 100 $k\Omega$, at 300 $K$, is around 50%. We
measure at 2 $K$ a hy... | 0411623v2 |
2004-12-13 | Unusual thermoelectric behavior of packed crystalline granular metals | Loosely packed granular materials are intensively studied nowadays.
Electrical and thermal transport properties should reflect the granular
structure as well as intrinsic properties. We have compacted crystalline $CaAl$
based metallic grains and studied the electrical resistivity and the
thermoelectric power as a funct... | 0412323v1 |
2004-12-23 | Large negative magnetoresistance in a ferromagnetic shape memory alloy : Ni_{2+x}Mn_{1-x}Ga | 5% negative magnetoresistance (MR) at room temperature has been observed in
bulk Ni_{2+x}Mn_{1-x}Ga. This indicates the possibility of using
Ni_{2+x}Mn_{1-x}Ga as magnetic sensors. We have measured MR in the
ferromagnetic state for different compositions (x=0-0.2) in the austenitic,
pre-martensitic and martensitic phas... | 0412646v3 |
2005-01-05 | Band-edge diagrams for strained III-V semiconductor quantum wells, wires, and dots | We have calculated band-edge energies for most combinations of zincblende
AlN, GaN, InN, GaP, GaAs, InP, InAs, GaSb and InSb in which one material is
strained to the other. Calculations were done for three different geometries,
quantum wells, wires, and dots, and mean effective masses were computed in
order to estimate... | 0501090v1 |
2005-01-19 | Magnetism and Transport in YbMn2Sb2 | A new ternary intermetallic compound, namely, YbMn2Sb2, has been synthesized
and its magnetic and electrical transport properties have been studied in the
temperature range of 2 to 300 K. This compound crystallizes in a trigonal,
La2O2S type structure (space group P3bm1, No. 164) and is found to be
ferromagnetically or... | 0501450v1 |
2005-01-21 | Velocity selection problem for combined motion of melting and solidification fronts | We discuss a free boundary problem for two moving solid-liquid interfaces
that strongly interact via the diffusion field in the liquid layer between
them. This problem arises in the context of liquid film migration (LFM) during
the partial melting of solid alloys. In the LFM mechanism the system chooses a
more efficien... | 0501521v1 |
2005-02-13 | Self-Organization and the Physics of Glassy Networks | Network glasses are the physical prototype for many self-organized systems,
ranging from proteins to computer science. Conventional theories of gases,
liquids, and crystals do not account for the strongly material-selective
character of the glass-forming tendency, the phase diagrams of glasses, or
their optimizable pro... | 0502312v1 |
2005-02-14 | Superconductivity induced by spark erosion in ZrZn2 | We show that the superconductivity observed recently in the weak itinerant
ferromagnet ZrZn2 [C. Pfleiderer et al., Nature (London) 412, 58 (2001)] is due
to remnants of a superconducting layer induced by spark erosion. Results of
resistivity, susceptibility, specific heat and surface analysis measurements on
high-qual... | 0502341v2 |
2005-03-02 | Higher Order Spectra in Avalanche Models | Utilizing the Haar transform, we study the higher order spectral properties
of mean field avalanche models, whose avalanche dynamics are described by
Poisson statistics at a critical point or critical depinning transition. The
Haar transform allows us to obtain a time series of noise powers, $H(f_1,t)$,
that gives impr... | 0503062v1 |
2005-03-30 | Stability of ferromagnetism in the half-metallic pnictides and similar compounds: A first-principles study | Based on first-principles electron structure calculations and employing the
frozen-magnon approximation we study the exchange interactions in a series of
transition-metal binary alloys crystallizing in the zinc-blende structure and
calculate the Curie temperature within both the mean-field approximation (MFA)
and rando... | 0503713v1 |
2005-04-08 | Influence of copper on the electronic properties of amorphous chalcogenides | We have studied the influence of alloying copper with amorphous arsenic
sulfide on the electronic properties of this material. In our
computer-generated models, copper is found in two-fold near-linear and
four-fold square-planar configurations, which apparently correspond to Cu(I)
and Cu(II) oxidation states. The numbe... | 0504207v1 |
2005-04-26 | Electron-phonon interaction for adiabatic anharmonic phonons | A model with Holstein-like electron-phonon coupling is studied in the limit
of adiabatic phonons. The phonon distribution is anharmonic with two degenerate
maxima. This model can be related to fermions in a correlated binary alloy and
describes microscopic phase separation. We discuss the weak and strong
electron-phono... | 0504688v2 |
2005-04-27 | Temperature and particle size dependence of equilibrium order parameter of FePt | First, second and third nearest neighbor pair mixing potentials for
equiatomic FePt alloys were calculated from first principles by the
Connolly-Williams method within the canonical cluster expansion formalism.
Using the mixing potentials obtained in this manner, the dependency of
equilibrium L1_0 ordering on temperatu... | 0504702v1 |
2005-04-28 | Multiple scattering formalism for correlated systems: A KKR+DMFT approach | We present a charge and self-energy self-consistent computational scheme for
correlated systems based on the Korringa-Kohn-Rostoker (KKR) multiple
scattering theory with the many-body effects described by the means of
dynamical mean field theory (DMFT). The corresponding local multi-orbital and
energy dependent self-en... | 0504760v1 |
2005-05-19 | Comparison of Measured and Calculated Specific Resistances of Pd/Pt Interfaces | We compare specific resistances (AR equals area A times resistance R) of
sputtered Pd/Pt interfaces measured in two different ways with
no-free-parameter calculations. One way gives 2AR(Pd/Pt) of 0.29 (0.03)
fohm-m(2) and the other 0.17 (0.13) fohm-m(2). From these we derive a best
estimate of 2AR(Pd/Pt) of 0.28 (0.06)... | 0505488v2 |
2005-05-25 | Strong electron-phonon coupling in delta-phase stabilized Pu | Heat capacity measurements of the delta-phase stabilized alloy Pu-Al suggest
that strong electron-phonon coupling is required to explain the moderate
renormalization of the electronic density of states near the Fermi energy. We
calculate the heat capacity contributions from the lattice and electronic
degrees of freedom... | 0505620v1 |
2005-06-29 | Non-Fermi liquid states in the pressurized $CeCu_2(Si_{1-x}Ge_x)_2$ system: two critical points | In the archetypal strongly correlated electron superconductor CeCu$_2$Si$_2$
and its Ge-substituted alloys CeCu$_2$(Si$_{1-x}$Ge$_{x}$)$_2$ two quantum
phase transitions -- one magnetic and one of so far unknown origin -- can be
crossed as a function of pressure \cite{Yuan 2003a}. We examine the associated
anomalous no... | 0506773v2 |
2005-07-04 | Suppression of ferromagnetism in URhGe doped with Ru | In the correlated metal URhGe ferromagnetic order (T_C = 9.5 K) and
superconductivity (T_s= 0.25 K) coexist at ambient pressure. Here we report on
alloying URhGe by Ru, which enables one to tune the Curie temperature to 0 K.
URuGe has a paramagnetic ground state and is isostructural to URhGe. We have
prepared a series ... | 0507068v1 |
2005-07-11 | Simulation and optimisation of terahertz emission from InGaAs and InP photoconductive switches | We simulate the terahertz emission from laterally-biased InGaAs and InP using
a three-dimensional carrier dynamics model in order to optimise the
semiconductor material. Incident pump-pulse parameters of current Ti:Sapphire
and Er:fibre lasers are chosen, and the simulation models the semiconductor's
bandstructure usin... | 0507252v2 |
2005-07-20 | Superconducting Proximity Effect through a Magnetic Domain Wall | We study the superconducting proximity effect in a
superconductor-ferromagnet-superconductor (SFS) heterostructure, containing a
domain wall in the ferromagnetic region. For the ferromagnet we assume an alloy
with an exchange splitting of the conduction bands comparable to the
superconducting gaps. We calculate the mod... | 0507482v1 |
2005-07-29 | ZnSe/GaAs(001) heterostructures with defected interfaces: structural, thermodynamic and electronic properties | We have performed accurate \emph{ab--initio} pseudopotential calculations for
the structural and electronic properties of ZnSe/GaAs(001) heterostructures
with interface configurations accounting for charge neutrality prescriptions.
Beside the simplest configurations with atomic interdiffusion we consider also
some conf... | 0507724v2 |
2005-08-04 | Direct observations of nucleation in a nondilute multicomponent alloy | The chemical pathways leading to gamma-prime(L1_2)-nucleation from nondilute
Ni-5.2 Al-14.2 Cr at.%, gamma(f.c.c.), at 873 K are followed with radial
distribution functions and isoconcentration surface analyses of direct-space
atom-probe tomographic images. Although Cr atoms initially are randomly
distributed, a distri... | 0508117v3 |
2005-08-29 | New limits on the ordered moments in alpha-Pu and Ga-stabilized delta-Pu | We present the first muon spin relaxation measurements ever performed on
elemental Pu, and set the most stringent upper limits to date on the magnitude
of the ordered moment in alpha-Pu and delta-stabilized Pu (alloyed with 4.3 at.
% Ga). Assuming a nominal hyperfine coupling field of 1 kOe per Bohr magneton
we set an ... | 0508694v1 |
2005-08-31 | Phase-field model for grain boundary grooving in multi-component thin films | Polycrystalline thin films can be unstable with respect to island formation
(agglomeration) through grooving where grain boundaries intersect the free
surface and/or thin film-substrate interface. We develop a phase-field model to
study the evolution of the phases, composition, microstructure and morphology
of such thi... | 0508746v1 |
2005-10-13 | The Mechanical Threshold Stress model for various tempers of AISI 4340 steel | Numerical simulations of high-strain-rate and high-temperature deformation of
pure metals and alloys require realistic plastic constitutive models. Empirical
models include the widely used Johnson-Cook model and the semi-empirical
Steinberg-Cochran-Guinan-Lund model. Physically based models such as the
Zerilli-Armstron... | 0510330v1 |
2005-11-08 | Nucleation and growth of second phase precipitates under non-isothermal conditions | The Langer-Schwartz equations for precipitation are formulated to calculate
nucleation, growth and coarsening of second phase precipitates under
non-isothermal situations. A field-theoretic steady-state nucleation rate model
is used in the analysis. The field-theoretic nucleation rate is compared with
the classical nuc... | 0511201v1 |
2005-12-23 | Magnetization-dependent $T_c$ shift in F/S/F trilayers with a strong ferromagnet | We have measured the superconducting transition temperature $T_c$ of Ni/Nb/Ni
trilayers when the magnetizations of the two outer Ni layers are parallel (P)
and antiparallel (AP). The largest difference in $T_c$ occurs when the Nb
thickness is just above the critical thickness at which superconductivity
disappears compl... | 0512623v1 |
2006-01-04 | Prospect for room temperature tunneling anisotropic magnetoresistance effect: density of states anisotropies in CoPt systems | Tunneling anisotropic magnetoresistance (TAMR) effect, discovered recently in
(Ga,Mn)As ferromagnetic semiconductors, arises from spin-orbit coupling and
reflects the dependence of the tunneling density of states in a ferromagnetic
layer on orientation of the magnetic moment. Based on ab initio relativistic
calculation... | 0601071v1 |
2006-01-05 | Anisotropic self-affine properties of experimental fracture surfaces | The scaling properties of post-mortem fracture surfaces of brittle (silica
glass), ductile (aluminum alloy) and quasi-brittle (mortar and wood) materials
have been investigated. These surfaces, studied far from the initiation, were
shown to be self-affine. However, the Hurst exponent measured along the crack
direction ... | 0601086v1 |
2006-01-09 | Quantum transport of slow charge carriers in quasicrystals and correlated systems | We show that the semi-classical model of conduction breaks down if the mean
free path of charge carriers is smaller than a typical extension of their
wavefunction. This situation is realized for sufficiently slow charge carriers
and leads to a transition from a metallic like to an insulating like regime
when scattering... | 0601145v2 |
2006-01-12 | Two-Dimensional Electron Gas in InGaAs/InAlAs Quantum Wells | We designed and performed low temperature DC transport characterization
studies on two-dimensional electron gases confined in lattice-matched
In$_{0.53}$Ga$_{0.47}$As/In$_{0.52}$Al$_{0.48}$As quantum wells grown by
molecular beam epitaxy on InP substrates. The nearly constant mobility for
samples with the setback dista... | 0601256v1 |
2006-02-02 | Electron transmission between normal and heavy electron metallic phases in a Kondo lattice system | The interface between a heavy electron coherent metallic phase and an
incoherent normal metal phase is discussed. The Fermi momentum mismatch between
the two phases causes the carriers to scatter at the interface. The interface
conductance is a monotonous increasing function of conduction electron density,
n_c, and is ... | 0602060v2 |
2006-02-19 | Re-entrant superconductivity in Nb/Cu(1-x)Ni(x) bilayers | We report on the first observation of a pronounced re-entrant
superconductivity phenomenon in superconductor/ferromagnetic layered systems.
The results were obtained using a superconductor/ferromagnetic-alloy bilayer of
Nb/Cu(1-x)Ni(x). The superconducting transition temperature T_{c} drops sharply
with increasing thic... | 0602448v1 |
2006-02-26 | Strong temperature dependence of antiferromagnetic coupling in CoFeB/Ru/CoFeB | The temperature dependence of saturation and spin-flop fields for artificial
ferrimagnets (AFi) based on antiparallel coupled CoFeB/Ru/CoFeB trilayers has
been investigated in a temperature range between 80K and 600K. The results
presented in this paper are relevant for magnetic devices using this system,
e.g. magnetic... | 0602609v2 |
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