publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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1997-01-15 | A mechanism for the non-Fermi-liquid behavior in CeCu_{6-x}Au_x | We propose an explanation for the recently observed non-Fermi-liquid behavior
of metallic alloys CeCu_{6-x}Au_x: near x=0.1, the specific heat c is
proportional to T \ln (T_0/T) and the resistivity increases linearly with
temperature T over a wide range of T. These features follow from a model in
which three-dimensiona... | 9701109v1 |
1997-01-31 | Investigation of the annealed disordered Ising systems within two-tail approximation | In the present paper an approach for investigation of the disordered
two-component Ising systems with long range interaction has been suggested.
Possible applications to metalic and magnetic alloys and lattice gas are
considered. We have also obtained numerical results for thermodynamical
properties of these models. Th... | 9702006v1 |
1997-03-03 | Evidence for Kondo Effect in Au80Co20 Ribbons | A minimum in resistivity as a function of temperature for an as-quenched
Au80Co20 ribbon prepared by melt-spinning using a wheel surface speed of 20 m
s^{-1} is found at 25 K. No resistivity minimum is found for an as-quenched
ribbon using a wheel surface speed of 60 m s^{-1}, however, upon heat treatment
of this ribbo... | 9703030v1 |
1997-03-07 | Multiple small angle neutron scattering in ferromagnets | The conclusions arising from the multiple small angle neutron scattering
theory, developed recently by S.V. Maleyev, R.V. Pomortsev and Y.N. Skryabin
[Phys. Rev. B 50 7133 (1994)] for the value of Born parameter more than 1, are
experimentally confirmed by magnetic scattering from domain structure of pure
Fe and Ni, as... | 9703064v1 |
1997-04-24 | Local Pairing at U-impurities in BCS Superconductors | We analyse here the role electrons on Anderson-U impurities play in
superconductivity in a metal alloy. We find that phonon coupling at impurities
counteracts the traditional effects which dominate T_c suppression in the
non-magnetic limit. In some cases, we findt hat non-magnetic impurities can
enhance T_c. In the Kon... | 9704207v2 |
1997-05-25 | Close Packing of Atoms, Geometric Frustration and the Formation of Heterogeneous States in Crystals | To describe structural peculiarities in inhomogeneous media caused by the
tendency to the close packing of atoms a formalism based on the using of the
Riemann geometry methods (which were successfully applied lately to the
description of structures of quasicrystals and glasses) is developed. Basing on
this formalism we... | 9705251v1 |
1997-06-07 | Tight-Binding study of the electronic and magnetic properties of an L1_0 ordered FeCu alloy | We have calculated the electronic structure of the tetragonal L1$_0$ ordered
FeCu by solving self-consistently a tight-binding Hamiltonian for s, p and d
electrons. We have found by total energy calculation that this structure is
ferromagnetic. In addition, we have determined that the equilibrium ratio
between the inte... | 9706071v1 |
1997-06-23 | Confined gap excitation and multielectron localization in magnetic alloys | The degenerate Anderson model with a nonlinear electron dispersion and an
energy dependent hybridization is proven to exhibit hidden integrability and is
diagonalized by the Bethe ansatz. If the impurity $f$-level energy lies below
the conduction band edge, the spectrum of the system is shown to contain pairs
of confin... | 9706230v1 |
1997-06-24 | Lattice Dynamics of Martensitic Transformations Examined by Atomistic Simulations | We have performaed molecular dynamics simulations of Fe(80)Ni(20) alloys
using an inter-atomic potential of the EAM-type which allows the simulation of
the martensite-austenite transition. We present results, showing the
development of an inhomogeneous shear system on a nanoscale during the
thermally induced austenitic... | 9706248v1 |
1997-07-02 | Bethe ansatz approach to thermodynamics of superconducting magnetic alloys | We derive thermodynamic Bethe ansatz equations for a model describing an
$U\to\infty$ Anderson impurity embedded in a BCS superconductor. The equations
are solved analytically in the zero-temperature limit, T=0. It is shown that
the impurities depress superconductivity in the Kondo limit, however at T=0 the
system rema... | 9707026v2 |
1997-09-26 | Dynamics of a ferromagnetic domain wall and the Barkhausen effect | We derive an equation of motion for the the dynamics of a ferromagnetic
domain wall driven by an external magnetic field through a disordered medium
and we study the associated depinning transition. The long-range dipolar
interactions set the upper critical dimension to be $d_c=3$, so we suggest that
mean-field exponen... | 9709300v1 |
1998-01-06 | Van Hove Singularity and D-Wave Pairing in Disordered Superconductors | We apply the coherent potential approximation (CPA) to a simple model for
disordered superconductors with d-wave pairing. We demonstrate that whilst the
effectiveness of an electronic Van Hove singularity to enhance the transition
temperature T$_c$ is reduced by disorder it is not eliminated. In fact we give
a qualitat... | 9801035v1 |
1998-02-06 | Magnetic Properties of Dilute Alloys: Equations for Magnetization and its Structural Fluctuations | The dilute Heisenberg ferromagnet is studied taking into account fluctuations
of magnetization caused by disorder. A self-consistent system of equations for
magnetization and its mean quadratic fluctuations is derived within the
configurationally averaged two-time temperature Green's function method. This
system of equ... | 9802073v1 |
1998-03-01 | Scaling of magnetic fluctuations near a quantum phase transition | We use inelastic neutron scattering to measure the magnetic fluctuations in a
single crystal of the heavy fermion alloy CeCu_5.9Au_0.1 close to the
antiferromagnetic quantum critical point. The energy and temperature-dependent
spectra obey (E/T) scaling at Q near (1,0,0). The neutron data and earlier bulk
susceptibilit... | 9803004v1 |
1998-03-06 | Coalescence of the Fermi-surface-related diffuse intensity peaks in disordered alloys | The possibility of disappearance of the diffuse-intensity peak splitting
induced by the Fermi surface (i.e., of coalescence of the intensity maxima)
with decreasing temperature is predicted. The underlying mechanism is the
compensation of the reciprocal-space curvatures of the self-energy and the
interaction. The theor... | 9803077v1 |
1998-05-07 | The first principles calculation of transport coefficients | We demonstrate the practical feasibility of calculating transport
coefficients such as the viscosity of liquids completely from first principles
using the Green-Kubo relations. Results presented for liquid aluminum are shown
to have a statistical error of only ca. 5%. The importance of such calculations
is illustrated ... | 9805082v1 |
1998-07-13 | Theoretical evidence for the semi-insulating character of AlN | We present ab initio density-functional calculations for acceptors, donors,
and native defects in aluminum nitride, showing that acceptors are deeper (Be ~
0.25 eV, Mg_ 0.45 eV) and less soluble than in GaN; at further variance with
GaN, both the extrinsic donors Si_Al and C_Al, and the native donor V_N (the
anion vaca... | 9807190v1 |
1998-08-20 | Barkhausen noise in soft amorphous magnetic materials under applied stress | We report experimental measurements of Barkhausen noise on
Fe_{64}Co_{21}B_{15} amorphous alloy under tensile stress. We interpret the
scaling behavior of the noise distributions in terms of the depinning
transition of the domain walls. We show that stress induced anisotropy enhance
the effect of short-range elastic in... | 9808224v1 |
1998-10-03 | Van der Waerden's Colouring Theorem and Weak-Strong Duality on the Lattice | Van der Waerden's (VDW) colouring theorem in combinatoric number theory [1]
has scope for physical applications.The solution of the two colour case has
enabled the construction of an explicit mapping of an infinite, one dimensional
antiferromagnetic Ising system to an effective pseudo- ferromagnetic one with
the coupli... | 9810030v1 |
1998-11-09 | Exact Thermodynamics of Disordered Impurities in Quantum Spin Chains | Exact results for the thermodynamic properties of ensembles of magnetic
impurities with randomly distributed host-impurity couplings in the quantum
antiferromagnetic Heisenberg model are presented. Exact calculations are done
for arbitrary values of temperature and external magnetic field. We have shown
that for strong... | 9811115v1 |
1998-11-29 | Stripe phase ordering as quantum interference phenomenon | A quantum interference mechanism of the stripe phase instability in quasi
one-dimensional (1D) repulsive electron system is proposed. The leading
spin-charge coupling term in Landau functional is derived microscopically. It
is shown that away from half filling, periodic lattice potential causes
cooperative condensation... | 9811409v1 |
1998-12-09 | Phonon-phason coupling in icosahedral quasicrystals | From relaxation simulations of decoration-based quasicrystal structure models
using microscopically based interatomic pair potentials, we have calculated the
(usually neglected) phonon-phason coupling constant. Its sign is opposite for
the two alloys studied, i-AlMn and i-(Al,Cu)Li; a dimensionless measure of its
magni... | 9812139v1 |
1998-12-11 | Band-Structure Effects in the Spin Relaxation of Conduction Electrons | Spin relaxation of conduction electrons in metals is significantly influenced
by the Fermi surface topology. Electrons near Brillouin zone boundaries,
special symmetry points, or accidental degeneracy lines have spin flip rates
much higher than an average electron. A realistic calculation and analytical
estimates show ... | 9812206v1 |
1999-01-26 | Phase separation and the segregation principle in the infinite-U spinless Falicov-Kimball model | The simplest statistical-mechanical model of crystalline formation (or alloy
formation) that includes electronic degrees of freedom is solved exactly in the
limit of large spatial dimensions and infinite interaction strength. The
solutions contain both second-order phase transitions and first-order phase
transitions (t... | 9901289v1 |
1999-03-20 | Crystal Field Triplets: A New Route to Non-Fermi Liquid Physics | A model for crystal field triplet ground states on rare earth or actinide
ions with dipolar and quadrupolar couplings to conduction electrons is studied
for the first time with renormalization group methods. The quadrupolar coupling
leads to a new nontrivial, non-Fermi liquid fixed point, which survives in an
intermedi... | 9903311v1 |
1999-09-23 | Level spacing statistics of disordered finite superlattices spectra and motional narrowing as a random matrix theory effect | In the present work the problem of coupled disordered quantum wells is
addressed in a random matrix theory framework. The quantum wells are short
repulsive binary alloys embeded by ordered barriers and show well defined
quantized levels as a consequence of spatial confinement. Finite disordered
superlattices may show b... | 9909341v1 |
1999-10-04 | Numerical studies of the vibrational isocoordinate rule in chalcogenide glasses | Many properties of alloyed chalcogenide glasses can be closely correlated
with the average coordination of these compounds. This is the case, for
example, of the ultrasonic constants, dilatometric softening temperature and
the vibrational densities of states. What is striking, however, is that these
properties are neve... | 9910032v1 |
1999-10-18 | Universal aspects of vacancy-mediated disordering dynamics: the effect of external fields | We investigate the disordering of an initially phase-segregated binary alloy,
due to a highly mobile defect which couples to an electric or gravitational
field. Using both mean-field and Monte Carlo methods, we show that the late
stages of this process exhibit dynamic scaling, characterized by a set of
exponents and sc... | 9910275v1 |
1999-12-08 | Dynamic scaling in vacancy-mediated disordering | We consider the disordering dynamics of an interacting binary alloy with a
small admixture of vacancies which mediate atom-atom exchanges. Starting from a
perfectly phase-segregated state, the system is rapidly heated to a temperature
in the disordered phase. A suitable disorder parameter, namely, the number of
broken ... | 9912135v1 |
1999-12-09 | Binding Energy of Impurity in a Size Quantized Coated Semiconductor Wire: Role of the Dielectric-Constant Mismatch | Within the framework of staircase infinitely deep (SIW) potential well model
the effect of dielectric constant mismatch between the size-quantized
semiconducting wire, coating and surrounding environment on impurity binding
energy is considered. Calculations are done in both the absence and presence of
magnetic field a... | 9912147v1 |
1999-12-10 | Excited States Calculated by Means of the Linear Muffin-Tin Orbital Method | The most popular electronic structure method, the linear muffin-tin orbital
method (LMTO), in its full-potential (FP) and relativistic forms has been
extended to calculate the spectroscopic properties of materials form first
principles, i.e, optical spectra, x-ray magnetic circular dichroism (XMCD) and
magneto-optical ... | 9912174v1 |
2000-01-13 | Scaling exponents for Barkhausen avalanches in polycrystals and amorphous ferromagnets | We investigate the scaling properties of the Barkhausen effect, recording the
noise in several soft ferromagnetic materials: polycrystals with different
grain sizes and amorphous alloys. We measure the Barkhausen avalanche
distributions and determine the scaling exponents. In the limit of vanishing
external field rate,... | 0001191v1 |
2000-02-07 | Interplay of Disorder and Correlations | I address here the question of the mutual interplay of strong correlations
and disorder in the system. I consider random version of the Hubbard model.
Diagonal randomness is introduced {\it via} random on-site energies and treated
by the coherent potential approximation. Strong, short ranged, electron -
electron intera... | 0002091v1 |
2000-02-14 | Spin-flux phase in the Kondo lattice model with classical localized spins | We provide numerical evidence that a spin-flux phase exists as a ground state
of the Kondo lattice model with classical local spins on a square lattice. This
state manifests itself as a double-Q magnetic order in the classical spins with
spin density at both $(0,\pi)$ and $(\pi,0)$ and further exhibits fermionic
spin c... | 0002211v1 |
2000-04-12 | Dipole scattering in polarization induced two-dimensional electron gases | Unusually large spontaneous and piezoelectric fields in the III-V nitrides
have led to the making of an entirely new class of two-dimensional electron
gas. Fluctuation from a perfectly periodic binary structure in highly polar
semiconductor alloys present the same physical situation as a random
distribution of microsco... | 0004204v1 |
2000-05-26 | Spin and charge excitations in incommensurate spin density waves | Collective excitations both for spin- and charge-channels are investigated in
incommensurate spin density wave (or stripe) states on two-dimensional Hubbard
model. By random phase approximation, the dynamical susceptibility
\chi(q,\omega) is calculated for full range of (q,\omega) with including all
higher harmonics co... | 0005466v1 |
2000-06-29 | Fermi-Edge Singularities in AlxGa1-xAs Quantum Wells : Extrinsic Versus Many-Body Scattering Processes | A Fano resonance mechanism is evidenced to control the formation of optical
Fermi-edge singularities in multi-subband systems such as remotely doped
AlxGa1-xAs heterostructures. Using Fano parameters, we probe the physical
nature of the interaction between Fermi-sea electrons and empty conduction
subbands. We show that... | 0006471v1 |
2000-07-17 | High-resolution Compton Scattering as a Probe of Fermiology and Electron Correlation Effects | Compton scattering is one of the few spectroscopies which directly probes the
ground state momentum density in materials. Recent progress in synchrotron
light sources has brought a renewed interest in the technique as a tool for
investigating fermiology related issues on the one hand, and as a unique window
on hitherto... | 0007277v1 |
2000-07-25 | Electronic structure and magnetism in disordered bcc Fe alloys | We here study electronic structure and magnetic properties of bcc
Co$_{x}$Fe$_{1-x}$, Cr$_{x}$Fe$_{1-x}$ and Mn$_{x}$Fe$_{1-x}$ in their
ferromagnetic phases using Augmented Space Recursion technique coupled with
tight-binding linearized muffin tin orbital (TB-LMTO) method. We make a
systematic study of magnetic proper... | 0007384v1 |
2000-11-13 | Theory of Adsorption on Metal Substrates | Contents:
5.1 Introduction
5.2 Concepts and definitions
5.3 The tight-binding picture of bonding
5.4 Adsorption of isolated adatoms
5.5 Alkali-metal adsorption: the traditional picture of on-surface adsorption
5.6 Substitutional adsorption and formation of surface alloys
5.7 Adsorption of CO on transition... | 0011217v1 |
2000-11-20 | Effects of Disorder on Ferromagnetism in Diluted Magnetic Semiconductors | We present results of a numerical mean field treatment of interacting spins
and carriers in doped diluted magnetic semiconductors, which takes into account
the positional disorder present in these alloy systems. Disorder is found to
enhance the ferromagnetic transition temperature significantly for metallic
densities n... | 0011319v2 |
2000-12-04 | Exchange Mediated Interaction of Dislocations and Deformation Hardening of Invar Alloys | We propose an explanation of anomalies observed in the behavior of
deformation hardening of Invars. An extremely strong volume magnetostriction,
typical of Invars, results in an enhancement of the exchange contribution to
the energy of the dislocation system by about three orders of magnitude with
respect to its value ... | 0012036v1 |
2000-12-07 | Possible Coexistence of Rotational and Ferroelectric Lattice Distortions in Rhombohedral PZT | The competitions between ferroelectric and rotational instabilities in
rhombohedral PZT near x = 0.5 are investigated using first principles density
functional supercell calculations. As expected, we find a strong ferroelectric
instability. However, we also find a substantial R-point rotational
instability, close to bu... | 0012126v1 |
2001-01-03 | The Physics of Electric Field Effect Thermoelectric Devices | We describe here a novel approach to the subject of thermoelectric devices.
The current best thermoelectrics are based on heavily doped semiconductors or
semimetal alloys. We show that utilization of electric field effect or
ferroelectric field effect, not only provides a new route to this problem,
bypassing the drawba... | 0101023v1 |
2001-02-06 | Observation of superconductivity in Y$_2$PdGe$_3$, structurally same as MgB$_2$ | The results of electrical resistance (1.4 - 300 K), magnetization (2-300 K)
and heat-capacity (2 - 50 K) measurements in Y$_2$PdGe$_3$, found to
crystallize in a AlB$_2$-derived hexagonalstructure, are reported. The results
establish that this compound is superconducting below 3 K. This obervation is
interesting consid... | 0102110v1 |
2001-04-24 | Spectral fluctuations of the atomic vibrations in glasses: random matrix theory and beyond | It is demonstrated on a realistic model of amorphous alloy
Si$_{0.9}$Ge$_{0.1}$ with 1000 atoms, that short-range spectral fluctuations of
propagons and diffusons are universal and in agreement with random matrix
theory. The universality ceases at distances greater than Thouless number
$N_T$, where propagons obey the A... | 0104464v1 |
2001-04-26 | On metallic ferromagnetism of a generalized Hubbard model with correlated hopping | In the paper a possibility of metallic ferromagnetic state realization in a
generalized Hubbard model with more complete accounting of electron-electron
interactions, in particular, the correlated hopping and exchange interaction
integrals is investigated. Recently obtained by means of mean-field
approximation single e... | 0104515v1 |
2001-05-17 | Anisotropy of p states and 11B nuclear spin-lattice relaxation in (Mg,Al)B2 | We calculated the nuclear spin-lattice relaxation rate in the (Mg,Al)B2
system and found that the orbital relaxation mechanism dominates over the
dipolar and Fermi-contact mechanisms in MgB2, whereas in AlB2 due to a smaller
density of states and strong anisotropy of boron p orbitals the relaxation is
completely determ... | 0105356v1 |
2001-06-04 | An analytical strong coupling approach in dynamical mean-field theory | In the limit of infinite spatial dimensions a thermodynamically consistent
theory of the strongly correlated electron systems, which is valid for
arbitrary value of the Coulombic interaction ($U<\infty$), is built. For the
Hubbard model the total auxiliary single-site problem exactly splits into four
subspaces, which d... | 0106044v2 |
2001-10-25 | Multiscale nature of hysteretic phenomena: Application to CoPt-type magnets | We suggest a workable approach for the description of multiscale
magnetization reversal phenomena in nanoscale magnets and apply it to CoPt-type
alloys. We show that their hysteretic properties are governed by two effects
originating at different length scales: a peculiar splitting of domain walls
and their strong pinn... | 0110526v2 |
2001-12-01 | Critical Dynamics of Burst Instabilities in the Portevin-Le Chatelier Effect | We investigate the Portevin-Le Chatelier effect (PLC), by compressing Al-Mg
alloys in a very large deformation range, and interpret the results from the
viewpoint of phase transitions and critical phenomena. The system undergoes two
dynamical phase transitions between intermittent (or "jerky") and "laminar"
plastic dyn... | 0112010v1 |
2002-01-09 | Hole-doped, High-Temperature Superconductors Li_{x}BC, Na_{x}BC and C_{x} : A Coherent-Potential-Based Prediction | Using density-functional-based methods, we show that the hole-doped
Li_{x}BC and Na_{x}BC in P6_{3}/mmc crystal structure and C_{x} in graphite
structure are capable of showing superconductivity, possibly with a T_{c} much
higher than that of
MgB_{2}. We use full-potential methods to obtain the optimized lattice
co... | 0201126v1 |
2002-02-11 | Reconstructed Momentum Density and Fermi Surface in Cu0.9Al0.1 | A reconstruction technique based on Radon transforms is used to obtain 3D
electron momentum density rho(p) using nine recently measured high-resolution
Compton profiles (CPs) from a Cu_{0.9}Al_{0.1} disordered alloy single crystal.
The method was also applied to nine corresponding theoretical CPs computed
within the KK... | 0202185v2 |
2002-04-05 | Nucleation and Bulk Crystallization in Binary Phase Field Theory | We present a phase field theory for binary crystal nucleation. In the
one-component limit, quantitative agreement is achieved with computer
simulations (Lennard-Jones system) and experiments (ice-water system) using
model parameters evaluated from the free energy and thickness of the interface.
The critical undercoolin... | 0204143v1 |
2002-07-18 | Ac susceptibility behaviour of Ce_2Pd_{1-x}Co_{x}Si_3 | We report the results of ac susceptibility chi measurements for various
compositions of the series, Ce_2Pd_{1-x}Co_xSi_3, in the polycrystalline form,
which has been previously reported to undergo a transformation from magnetic
ordering to non-magnetic Kondo lattice behavior as x is varied from 0 to 1. A
finding of emp... | 0207447v1 |
2002-08-15 | Superconductivity in Ba_2Sn_3Sb_6 and SrSn_3Sb_4 | Resistivity and ac magnetic susceptibility measurements on Ba2Sn3Sb6 and
SrSn3Sb4 indicate that these Zintl compounds display a transition to a
superconducting phase at Tc = 3.9 K. The Meissner effect was observed for
Ba2Sn3Sb6 under an applied field of 25 Oe. The signatures for
superconductivity, such as high and low ... | 0208313v1 |
2002-09-24 | Dilatometric study of Ni2+xMn1-xGa under magnetic field | A study of polycrystalline and single crystalline Ni$_{2+x}$Mn$_{1-x}$Ga
alloys by means of dilatometric and strain gage techniques shows that large
strain can be induced in the temperature range of the martensitic
transformation by application of an external magnetic field. The biggest strain
induced by magnetic field... | 0209545v1 |
2002-09-26 | Ordering intermetallic alloys by ion irradiation: a way to tailor magnetic media | Combining He ion irradiation and thermal mobility below 600K, we both trigger
and control the transformation from chemical disorder to order in thin films of
an intermetallic ferromagnet (FePd). Kinetic Monte Carlo simulations show how
the initial directional short range order determines order propagation.
Magnetic ord... | 0209612v1 |
2003-03-27 | The Frequency Dependent Conductivity of Electron Glasses | Results of DC and frequency dependent conductivity in the quantum limit, i.e.
hw > kT, for a broad range of dopant concentrations in nominally uncompensated,
crystalline phosphorous doped silicon and amorphous niobium-silicon alloys are
reported. These materials fall under the general category of disordered
insulating ... | 0303589v1 |
2003-05-07 | Two-way shape memory effect and mechanical properties of Pulse Discharge Sintered Ni2.18Mn0.82Ga | Mechanical and shape memory properties of a polycrystalline Ni2.18Mn0.82Ga
alloy prepared by a PDS (Pulse Discharge Sintering) method were investigated.
It was found that the material demonstrates the two-way shape memory effect
after a loading - unloading cycle performed in the martensitic state, i. e.
essentially wit... | 0305123v1 |
2003-06-19 | Prepyramid-to-pyramid transition of SiGe islands on Si(001) | The morphology of the first three-dimensional islands appearing during
strained growth of SiGe alloys on Si(001) was investigated by scanning
tunneling microscopy. High resolution images of individual islands and a
statistical analysis of island shapes were used to reconstruct the evolution of
the island shape as a fun... | 0306491v2 |
2003-07-19 | Disordered Kondo Nanoclusters: Effect of Energy Spacing | Exact diagonalization results for Kondo nanoclusters alloyed with mixed
valence impurities show that tuning the {\it energy spacing}, $\Delta$, drives
the system from the Kondo to the RKKY regime. The interplay of $\Delta$ and
disorder gives rise to a $\Delta$ versus concentration T=0 phase diagram very
rich in structu... | 0307486v1 |
2003-08-01 | Aging, Fragility and Reversibility Window in Bulk Alloy Glasses | Non-reversing relaxation enthalpies (DHnr) at glass transitions Tg(x) in the
PxGexSe1-2x ternary display a wide, sharp and deep global minimum (~0) in the
0.09 < x < 0.145 range, within which Tg becomes thermally reversing. In the
reversibility window these glasses are found not to age, in contrast to aging
observed fo... | 0308016v1 |
2003-08-08 | Nuclear Spin Relaxation Rate of Disordered $p_x+ip_y$-wave Superconductors | Based on an effective Hamiltonian with the binary alloy disorder model
defined in the triangular lattice, the impurity scattering effects on the
density of states and especially on the spin-lattice relaxation rate $1/T_1$ of
$p_x+ip_y$-wave superconductors are studied by solving numerically the
Bogoliubov-de Gennes equ... | 0308160v1 |
2003-09-08 | Landau Theory For Shape Memory Polycrystals | We propose a Ginzburg-Landau theory for the elastic properties of shape
memory polycrystals. A single crystal elastic free energy for a system that
undergoes a square-to-rectangle transformation is generalized to a polycrystal
by introducing a crystal orientational field that is determined from a
continuum phase field ... | 0309206v1 |
2003-09-30 | High pressure phases in highly piezoelectric Pb(Zr0.52Ti0.48)O3 | Two novel room-temperature phase transitions are observed, via synchrotron
x-ray diffraction and Raman spectroscopy, in the Pb(Zr0.52Ti0.48)O3 alloy under
hydrostatic pressures up to 16 GPa. A monoclinic (M)-to-rhombohedral (R1) phase
transition takes place around 2-3 GPa, while this R1 phase transforms into
another rh... | 0309705v1 |
2003-10-06 | Ferromagnetism in (In,Mn)As alloy thin films grown by metalorganic vapor phase epitaxy | Ferromagnetic properties of In1-xMnxAs thin films were investigated. Room
temperature ferromagnetic order was observed in nominally single-phase films
with x = 0.01-0.10. Magnetization measurements indicated that these In1-xMnxAs
samples had a Curie temperature of 333 K. The Curie temperature was independent
of Mn conc... | 0310104v1 |
2003-11-03 | Inverted current-driven switching in Fe(Cr)/Cr/Fe(Cr) nanopillars | From both theory and experiment, scattering of minority electrons is expected
to be weaker than scattering of majority electrons in both dilute Fe(Cr) alloys
and at Fe(Cr)/Cr interfaces. We show that Fe(Cr)/Cr/Fe(Cr) trilayer nanopillars
display a normal magnetoresistance--i.e., largest resistance at low magnetic
field... | 0311047v1 |
2003-11-25 | Remarks about the Zeeman splitting in quantum dots and single atom transistors | An empirical formula is proposed to calculate the Kondo temperature in
quantum point contacts from the Zeeman splitting. A similar formula was used in
the point-contact spectroscopy (PCS) method to obtain from the Zeeman splitting
of the Kondo peak in the characteristics of the classical Kondo alloys AuFe and
CuMn [1].... | 0311578v1 |
2003-12-31 | Symmetry reduction in the augmented space recursion formalism for random binary alloys | We present here an efficient method which systematically reduces the rank of
the augmented space and thereby helps to implement augmented space recursion
for any real calculation. Our method is based on the symmetry of the
Hamiltonian in the augmented space and keeping recursion basis vectors in the
irreducible subspac... | 0312714v1 |
2004-02-03 | The Fermi Surface Effect on Magnetic Interlayer Coupling | The oscillating magnetic interlayer coupling of Fe over spacer layers
consisting of Cu$_{x}$Pd$_{1-x}$ alloys is investigated by first principles
density functional theory. The amplitude, period and phase of the coupling, as
well as the disorder-induced decay, are analyzed in detail and the consistency
to the Ruderman-... | 0402093v1 |
2004-02-13 | Intersite elastic coupling and invar effect | The invar phenomenon (very small thermal expansion in some iron alloys or
compounds) is usually explained by the thermally-induced transitions between
different spin states of Fe, having different atomic volumes. We consider these
processes taking into account elastic interaction between Fe atoms in different
spin stat... | 0402374v1 |
2004-03-09 | Pomeranchuk effect in unstable Ytterbium systems | $YbInCu_{4}$ and its alloys present discontinuous, first order iso-structural
transitions at pressure dependent temperatures $T_V(P)$, where a local moment
phase coexist with a renormalized Fermi liquid phase. We show that along the
coexistence line $T_V(P)$ the entropy of the large volume renormalized Fermi
liquid pha... | 0403251v1 |
2004-04-16 | Changes in magnetic scattering anisotropy at a ferromagnetic/superconducting interface | We show that some metals and alloys (X = Cu, Ag, FeMn, or Cu and Ag combined
with each other), sputtered between ferromagnetic Co and superconducting Nb,
produce no change in current-perpendicular-to-plane magnetoresistance (CPP-MR)
in a carefully designed CPP-spin-valve. In contrast, other metals (Ru or Au) or
combina... | 0404396v1 |
2004-07-28 | Planar Solidification from Undercooled Melt: An Approximation of a Dilute Binary Alloy for a Phase-field Model | Planar solidification from an undercooled melt has been considered using the
phase-field model. The solute and the phase fields have been found in the limit
of small impurity concentration. These solutions in the limit of vanishing
velocity of the interface motion give the equilibrium partition coefficient and
the liqu... | 0407721v1 |
2004-08-06 | Electronic and magnetic properties of the (111) surfaces of NiMnSb | Using an ab-initio electronic structure method, I study the (111) surfaces of
the half-metallic NiMnSb alloy. In all cases there is a very pronounced surface
state within the minority gap which destroys the half-metallicity This state
survives for several atomic layers below the surface contrary to the (001)
surfaces w... | 0408131v1 |
2004-08-12 | Spin Screening and Antiscreening in a Ferromagnet/Superconductor Heterojunction | We present a theoretical study of spin screening effects in a
ferromagnet/superconductor (F/S) heterojunction. It is shown that the magnetic
moment of the ferromagnet is screened or antiscreened, depending on the
polarization of the electrons at the Fermi level. If the polarization is
determined by the electrons of the... | 0408273v1 |
2004-09-28 | Stochastic phase-field simulations of symmetric alloy solidification | We study initial transient stages in directional solidification by means of a
non-variational phase field model with fluctuations. This model applies for the
symmetric solidification of dilute binary solutions and does not invoke
fluctuation-dissipation theorem to account for the fluctuation statistics. We
devote our a... | 0409713v1 |
2004-10-01 | Magnetic properties and thermal expansion of YbGa$_x$Ge$_{2-x}$ (0.9 <= x <= 1.5) | The composition dependence of the Yb valence and of the thermal expansion
have been studied in the YbGa$_x$Ge$_{2-x}$ system. X-ray diffraction reveals
that single-phased samples isostructural to YbGaGe are obtained in the range of
0.9 <= x <= 1.5. The magnetic susceptibility shows that the systems are almost
nonmagnet... | 0410007v1 |
2004-10-12 | Investigation of Dilute Magnetic Systems with Spin-1 Ising Model in the Frame of Generalized Statistical Mechanics | In this study the magnetization phenomenon has been investigated as a
behavior of interacting elementary moments ensemble, with the help of Ising
model [1] in the frame of non-extensive statistical mechanics. To investigate
the physical systems with three states and two order parameters, the spin-1
single lattice Ising... | 0410275v1 |
2004-11-18 | Coarse-grained Description of Polymer Blends as Interacting Soft-Colloidal Particles | We present a theoretical approach which maps polymer blends onto mixtures of
soft-colloidal particles. The analytical mesoscale pair distribution functions
reproduce well data from united atom molecular dynamics simulations of
polyolefin mixtures without fitting parameters. The theory exactly recovers the
analytical ex... | 0411497v1 |
2004-11-19 | Ab initio theory of Cr$_2$O$_3$ surface chemistry in solution | Using a new form of density functional theory for the {\em ab initio}
description of electronic systems in contact with a dielectric environment, we
present the first detailed study of the impact of a solvent on the surface
chemistry of Cr$_2$O$_3$, the passivating layer of stainless steel alloys.
Compared to vacuum, w... | 0411523v1 |
2005-01-06 | Catastrophic Fermi surface reconstruction in the shape-memory alloy AuZn | AuZn undergoes a shape-memory transition at 67 K. The de Haas van Alphen
effect persists to 100 K enabling the observation of a change in the quantum
oscillation spectrum indicative of a catastrophic Fermi surface reconstruction
at the transition. Coexistence of both Fermi surfaces at low temperatures is
suggestive of ... | 0501108v1 |
2005-01-20 | The Anomalous Hall effect in re-entrant AuFe alloys and the real space Berry phase | The Hall effect has been studied in a series of AuFe samples in the
re-entrant concentration range, as well as in the spin glass range. The data
demonstrate that the degree of canting of the local spins strongly modifies the
anomalous Hall effect, in agreement with theoretical predictions associating
canting, chirality... | 0501482v1 |
2005-02-23 | Ivantsov parabolic solution for two combined moving interfaces | We demonstrate that for a migration of a liquid layer between the melting and
the solidification front an exact steady-state solution with two parabolic
fronts can be found. A necessary condition hereby is that the temperature of
the solidification front exceeds the temperature of the melting front (both
temperatures a... | 0502551v1 |
2005-02-23 | Is the Mott transition relevant to f-electron metals ? | We study how a finite hybridization between a narrow correlated band and a
wide conduction band affects the Mott transition. At zero temperature, the
hybridization is found to be a relevant perturbation, so that the Mott
transition is suppressed by Kondo screening. In contrast, a first-order
transition remains at finit... | 0502563v1 |
2005-03-07 | Local density of states of a strongly type-II d-wave superconductor: The binary alloy model in a magnetic field | We calculate self-consistently the local density of states (LDOS) of a d-wave
superconductor considering the scattering of the quasiparticles off randomly
distributed impurities and off externally induced vortices. The impurities and
the vortices are randomly distributed but the vortices are preferably located
near the... | 0503164v1 |
2005-05-24 | The unusual temperature dependence of the Eu$^{2+}$ fluorescence lifetime in CaF$_2$ crystals | Fluorescence lifetimes of Eu$^{2+}$ doped in CaF$_2$ are measured at various
temperatures between 4K and 450K. The lifetime increases with between 100K and
300K, in contrast to the usual lifetime-temperature dependence. At higher or
lower temperatures the lifetime decreases with increasing temperature. The
phenomenon i... | 0505592v1 |
2005-07-11 | Electron-induced stabilization of ferromagnetism in GaGdN | Using {\it ab initio} band structure calculations and symmetry arguments, we
show that the magnetic property of Ga$_{1-x}$Gd$_x$N is drastically different
from TM-doped GaN. The coupling between Gd atoms in the alloy is
antiferromagnetic, but the ferromagnetic phase can be stabilized by introducing
electrons. Furthermo... | 0507257v1 |
2005-08-25 | EMR Measurements of Field-Induced Superconductor lamda-(BETS)2FexGa1-xCl4 | We have performed high-field Electron Magnetic Resonance (EMR) measurements
of lamda-(BETS)2FexGa1-xCl4 to clarify the role of Pi- and d-electrons in the
paramagnetic (PM) and field-induced superconducting (FISC) phases. We found
that this system has a non-negligible Pi-d interaction that is very sensitive
to the sampl... | 0508593v1 |
2005-10-07 | Perpendicular magnetic anisotropy in nanoclusters caused by surface segregation and shape | The growth of binary alloy clusters on a weakly interacting substrate through
codeposition of two atomic species is studied by kinetic Monte Carlo
simulation. Our model describes salient features of CoPt$_3$-nanoclusters, as
obtained recently by the molecular-beam epitaxy technique. The clusters display
perpendicular m... | 0510196v1 |
2005-12-07 | Effect of spin-orbit interaction on a magnetic impurity in the vicinity of a surface | We propose a new mechanism for surface-induced magnetic anisotropy to explain
the thickness-dependence of the Kondo resistivity of thin films of dilute
magnetic alloys. The surface anisotropy energy, generated by spin-orbit
coupling on the magnetic impurity itself, is an oscillating function of the
distance d from the ... | 0512154v1 |
2005-12-18 | Spin Glasses: a Perspective | A brief personal perspective is given of issues, questions, formulations,
methods, some answers and selected extensions posed by the spin glass problem,
showing how considerations of an apparently insignificant and practically
unimportant group of metallic alloys stimulated an explosion of new insights
and opportunitie... | 0512425v2 |
2005-12-29 | Insulator-metal-insulator transition and selective spectral weight transfer in a disordered strongly correlated system | We investigate the metal insulator transitions at finite temperature for the
Hubbard model with diagonal alloy disorder. We solve the dynamical mean field
theory equations with the non crossing approximation and we use the coherent
potential approximation to handle disorder. The excitation spectrum is given
for various... | 0512702v1 |
2005-12-31 | Physical nature of fcc-bcc martensitic transformation in iron based alloys | The summary of the models offered by the author revealing features of the
physical mechanisms controlling processes of martensite crystal formation is
resulted. The rapid growth of a cooling martensite crystal is considered as a
self-organized process controlled by the quasi-longitudinal lattice
displacement waves (DW)... | 0601002v1 |
2006-01-13 | Influence of Roughness and Disorder on Tunneling Magnetoresistance | A systematic, quantitative study of the effect of interface roughness and
disorder on the magnetoresistance of FeCo$|$vacuum$|$FeCo magnetic tunnel
junctions is presented based upon parameter-free electronic structure
calculations. Surface roughness is found to have a very strong effect on the
spin-polarized transport ... | 0601291v2 |
2006-01-19 | Electron-phonon coupling in the two phonon mode ternary alloy $Al_{0.25}In_{0.75}As/Ga_{0.25}In_{0.75}As$ quantum well | We have investigated the infrared transmission of a two-dimensional (2DEG)
electron gas confined in a $Al_{0.25}In_{0.75}As/Ga_{0.25}In_{0.75}As$ single
quantum well in order to study the electron optical phonon interaction in a two
phonon mode system. Infrared transmission experiments have been performed in
both the p... | 0601441v1 |
2006-02-15 | Physical meaning and measurement of the entropic parameter $q$ in an inhomogeneous magnetic systems | In this paper we present a thorough analysis of two systems magnetically
inhomogeneous: the manganite La$_{0.7}$Sr$_{0.3}$MnO$_3$/MgO and the amorphous
alloy Cu$_{90}$Co$_{10}$. In both cases, the non-extensive statistics yield a
faithful description of the magnetic behavior of the systems. In the model
proposed here, ... | 0602354v1 |
2006-03-07 | Phase-field modelling of solute trapping during rapid solidification of a Si-As alloy | The effect of nonequilibrium solute trapping by a growing solid under rapid
solidification conditions is studied using a phase-field model. Considering a
continuous steady-state concentration profile across the diffuse solid-liquid
interface, a new definition of the nonequilibrium partition coefficient in the
phase-fie... | 0603170v2 |
2006-03-09 | High Frequency dynamics in metallic glasses | Using Inelastic X-ray Scattering we studied the collective dynamics of the
glassy alloy Ni$_{33}$Zr$_{67}$ in the first pseudo Brillouin zone, an
energy-momentum region still unexplored in metallic glasses. We determine key
properties such as the momentum transfer dependence of the sound velocity and
of the acoustic da... | 0603251v1 |
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