publicationDate stringlengths 1 2.79k | title stringlengths 1 36.5k ⌀ | abstract stringlengths 1 37.3k ⌀ | id stringlengths 9 47 |
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2006-08-03 | The intergalactic propagation of ultra-high energy cosmic ray nuclei | We investigate the propagation of ultra-high energy cosmic ray nuclei (A =
1-56) from cosmologically distant sources through the cosmic radiation
backgrounds. Various models for the injected composition and spectrum and of
the cosmic infra-red background are studied using updated photo-disintegration
cross-sections. Th... | 0608085v4 |
2006-08-16 | Pinning Down Gravitational Settling | We analyse high-resolution archival UVES data of turnoff and subgiant stars
in the nearby globular cluster NGC 6397 ([Fe/H] = -2). Balmer-profile analyses
are performed to derive reddening-free effective temperatures. Due to the
limited S/N and uncertainties related to blaze removal, we find the data
quality insufficie... | 0608338v1 |
2006-08-16 | Sensitivity of p-Process Nucleosynthesis to Nuclear Reaction Rates in a 25 Solar Mass Supernova Model | The astrophysical p process, which is responsible for the origin of the
proton rich stable nuclei heavier than iron, was investigated using a full
nuclear reaction network for a type II supernova explosion when the shock front
passes through the O/Ne layer. Calculations were performed with a multi-layer
model adopting ... | 0608341v1 |
2006-08-31 | Galactic chemical evolution: Carbon through Zinc | We calculate the evolution of heavy element abundances from C to Zn in the
solar neighborhood adopting our new nucleosynthesis yields. Our yields are
calculated for wide ranges of metallicity (Z=0-Z_\odot) and the explosion
energy (normal supernovae and hypernovae), based on the light curve and spectra
fitting of indiv... | 0608688v1 |
2006-09-01 | Oxygen abundances in the Galactic Bulge: evidence for fast chemical enrichment | AIMS: We spectroscopically characterize the Galactic Bulge to infer its star
formation timescale, compared to the other Galactic components, through the
chemical signature on its individual stars.
METHODS: We derived iron and oxygen abundances for 50 K giants in four fields
towards the Galactic bulge. High resolution... | 0609052v2 |
2006-09-06 | The Supernova -- Gamma-Ray Burst Connection | Observations show that at least some gamma-ray bursts (GRBs) happen
simultaneously with core-collapse supernovae (SNe), thus linking by a common
thread nature's two grandest explosions. We review here the growing evidence
for and theoretical implications of this association, and conclude that most
long-duration soft-sp... | 0609142v1 |
2006-09-14 | The Formation of the Double Pulsar PSR J0737-3039A/B | Recent timing observations of the double pulsar J0737-3039A/B have shown that
its transverse velocity is extremely low, only 10 km/s, and nearly in the Plane
of the Galaxy. With this new information, we rigorously re-examine the history
and formation of this system, determining estimates of the pre-supernova
companion ... | 0609416v2 |
2006-09-19 | On the Origin of the Type Ia Supernova Width-Luminosity Relation | Brighter Type Ia supernovae (SNe Ia) have broader, more slowly declining
B-band light curves than dimmer SNe Ia. We study the physical origin of this
width-luminosity relation (WLR) using detailed radiative transfer calculations
of Chandrasekhar mass SN Ia models. We find that the luminosity dependence of
the diffusion... | 0609540v1 |
2006-09-23 | Theoretical aspects of relativistic spectral features | The inner parts of black-hole accretion discs shine in X-rays which can be
monitored and the observed spectra can be used to trace strong gravitational
fields in the place of emission and along paths of light rays. This paper
summarizes several aspects of how the spectral features are influenced by
relativistic effects... | 0609645v1 |
2006-09-27 | The XMM-Newton RGS spectrum of the high luminosity Seyfert 1 galaxy Markarian 509 | We present a detailed analysis of the soft X-ray spectrum of the Seyfert 1
galaxy Markarian 509 taken with the XMM-Newton Reflection Grating Spectrometer.
An underlying power-law continuum and three warm absorber phases provide a good
fit to the data along with a number of broad and narrow emission lines. Our
three war... | 0609746v1 |
2006-09-29 | On SN 2003fg: The Probable Super-Chandrasekhar-Mass SN Ia | Howell et al. have reported the discovery of SN Ia SN 2003fg (SNLS-03D3bb)
and conclude that SN 2003fg is very likely a super-Chandrasekhar-mass SN Ia
perhaps with a mass of order 2 solar masses. Their work is the first strong
evidence that has been presented for a super-Chandrasekhar SN Ia. We have
performed an analys... | 0609804v3 |
2006-10-13 | r-Process Enhanced Halo Stars | Abundance observations indicate the presence of rapid-neutron capture (i.e.,
r-process) elements in old Galactic halo and globular cluster stars. These
observations provide insight into the nature of the earliest generations of
stars in the Galaxy -- the progenitors of the halo stars -- responsible for
neutron-capture ... | 0610412v1 |
2006-10-27 | Computation of the Fourier parameters of RR Lyrae stars by template fitting | Due to the importance of accurate Fourier parameters, we devise a method that
is more appropriate for deriving these parameters on low-quality data than the
traditional Fourier fitting. Based on the accurate light curves of 248
fundamental mode RR Lyrae stars, we test the power of a full-fetched
implementation of the t... | 0610823v1 |
2006-11-01 | Amplification and variability of the AGN X-ray emission due to microlensing | We consider the contribution of microlensing to the AGN Fe K$\alpha$ line and
X-ray continuum amplification and variation. To investigate the variability of
the line and X-ray continuum, we studied the effects of microlensing on quasar
X-ray spectra produced by crossing of a microlensing pattern across a standard
relat... | 0611016v1 |
2006-11-23 | Two Disk Components from a Gas Rich Disk-Disk Merger | We employ N-body, smoothed particle hydrodynamical simulations, including
detailed treatment of chemical enrichment, to follow a gas-rich merger which
results in a galaxy with disk morphology. We trace the kinematic, structural
and chemical properties of stars formed before, during, and after the merger.
We show that s... | 0611748v1 |
2006-11-28 | XMM-Newton study of 0.012<z<0.024 groups. I: Overview of the IGM thermodynamics | We study the thermodynamic properties of the hot gas in a sample of groups in
the 0.012-0.024 redshift range, using XMM-Newton observations. We present
measurements of temperature, entropy, pressure and iron abundance.
Non-parametric fits are used to derive the mean properties of the sample and to
study dispersion in t... | 0611846v2 |
2006-11-28 | The Two-dimensional XMM-Newton Group Survey: z<0.012 groups | We present the results of the 2-dimensional XMM-Newton Group Survey (2dXGS),
an archival study of nearby galaxy groups. In this paper we consider eleven
nearby systems (z<0.012) in Mulchaey et al. (2003), which span a broad range in
X-ray luminosity from 10^40 to 10^43 ergs/s. We measure the iron abundance and
temperat... | 0611858v1 |
2006-12-12 | Search for narrow energy-shifted lines in XMM-Newton AGN spectra | The detection of X-ray narrow spectral features in the 5-7 keV band is
becoming increasingly more common in AGN observations, thanks to the
capabilities of current X-ray satellites. Such lines, both in emission and in
absorption, are mostly interpreted as arising from Iron atoms. When observed
with some displacement fr... | 0612317v1 |
2006-12-15 | Non-LTE Models for Neutron Star Atmospheres and Supernova-Fallback Disks | We describe our recent progress in modeling supernova-fallback disks and
neutron star (NS) atmospheres.
We present a first detailed spectrum synthesis calculation of a SN-fallback
disk composed of iron. We assume a thin disk with a radial structure described
by the alpha-disk model. The vertical structure and emissio... | 0612425v1 |
2006-12-28 | Heating of Heavy Ions by Interplanetary Coronal Mass Ejection (ICME) Driven Collisionless Shocks | Shock heating and particle acceleration processes are some of the most
fundamental physical phenomena of plasma physics with countless applications in
laboratory physics, space physics, and astrophysics. This study is motivated by
previous observations of non-thermal heating of heavy ions in astrophysical
shocks (Korre... | 0612767v1 |
2007-01-05 | Ruling out a massive-assymptoic giant-branch star as the progenitor of supernova 2005cs | We calculate the predicted UBVRIJHK absolute magnitudes for models of
supernova progenitors and apply the result to the case of supernova 2005cs. We
agree with previous results that the initial mass of the star was of low,
around 6 to 8 M(sun). However such stars are thought to go through second
dredge-up to become AGB... | 0701152v1 |
2007-01-07 | Modeling the X-ray fractional variability spectrum of Active Galactic Nuclei using multiple flares | Using Monte-Carlo simulations of X-ray flare distributions across the
accretion disk of active galactic nuclei (AGN), we obtain modeling results for
the energy-dependent fractional variability amplitude. Referring to previous
results of this model, we illustrate the relation between the shape of the
point-to-point frac... | 0701164v1 |
2007-01-07 | Ultrahigh energy cosmic rays as heavy nuclei from cluster accretion shocks | Large-scale accretion shocks around massive clusters of galaxies, generically
expected in the cold dark matter scenario of cosmological structure formation,
are shown to be plausible sources of the observed ultrahigh energy cosmic rays
(UHECRs) by accelerating a mixture of heavy nuclei including the iron group
elements... | 0701167v3 |
2007-01-14 | Interstellar Iron and Silicon Depletions in Translucent Sight Lines | We report interstellar FeII and SiII column densities toward six translucent
sight lines (A_V >~ 1) observed with the Space Telescope Imaging Spectrograph
(STIS). The abundances were determined from the absorption of SiII] at 2335
Angstroms, and several weak Fe transitions including the first reported
detections of the... | 0701408v1 |
2007-01-19 | Exploring the X-ray spectral variability of MCG-6-30-15 with XMM-Newton | We present a study of the spectral variability of the Seyfert I galaxy
MCG-6-30-15 based on the two long XMM-Newton observations from 2000 and 2001.
The X-ray spectrum and variability properties of the 2001 data have previously
been well described with a two-component model consisting of a variable power
law and a much... | 0701567v1 |
2007-01-20 | The origin of the ankle | The differential intensity of cosmic radiation shows a sequence of
depressions referred to as "knees" in a large energy band above 10^15 eV. The
global depression entailed in the complete spectrum with respect to the
extrapolated intensity based on low energy data amounts to a maximum factor of
8, occurring at 5 x 10^1... | 0701593v1 |
2007-01-23 | INTEGRAL Observations of the Vela Region Focusing on Vela X-1 | The Vela region has been observed for 1.7 Ms in November 2005 by the INTEGRAL
satellite. We present preliminary spectral and temporal results of Vela X-1, an
eclipsing neutron star hosted in a wind-accreting high-mass X-ray binary
system. Using data from ISGRI, SPI and JEM-X, we firmly confirm the existence
of cyclotro... | 0701641v1 |
2007-01-26 | First ground based measurement of atmospheric Cherenkov light from cosmic rays | A recently proposed novel technique for the detection of cosmic rays with
arrays of Imaging Atmospheric Cherenkov Telescopes is applied to data from the
High Energy Stereoscopic System (H.E.S.S.). The method relies on the ground
based detection of Cherenkov light emitted from the primary particle prior to
its first int... | 0701766v1 |
2007-03-10 | Constraining global parameters of accreting black holes by modeling magnetic flares | We present modeling results for the reprocessed radiation expected from
magnetic flares above AGN accretion disks. Relativistic corrections for the
orbital motion of the flare and for the curved space-time in the vicinity of
the black hole are taken into account. We investigate the local emission
spectra, as seen in a ... | 0703240v1 |
2007-03-14 | Absorption Measure Distribution of the Outflow in IRAS 13349+2438: Direct Observation of Thermal Instability? | We analyze the Chandra X-ray spectrum obtained with the HETGS grating
spectrometer of IRAS 13349+2438, which has one of the richest absorption
spectra of a quasar outflow. Absorption from almost all charge states of Fe is
detected. This allows for a detailed reconstruction of the absorption measure
distribution (AMD), ... | 0703351v1 |
2007-03-14 | Delayed detonations in full-star models of Type Ia supernova explosions | Aims: We present the first full-star three-dimensional explosion simulations
of thermonuclear supernovae including parameterized deflagration-to-detonation
transitions that occur once the flame enters the distributed burning regime.
Methods: Treating the propagation of both the deflagration and the detonation
waves in ... | 0703378v1 |
2007-03-19 | Stokes diagnostics of simulated solar magneto-convection | We present results of synthetic spectro-polarimetric diagnostics of radiative
MHD simulations of solar surface convection with magnetic fields. Stokes
profiles of Zeeman-sensitive lines of neutral iron in the visible and infrared
spectral ranges emerging from the simulated atmosphere have been calculated in
order to st... | 0703490v1 |
2007-03-22 | Statistical methods applied to composition studies of ultrahigh energy cosmic rays | The mass composition of high energy cosmic rays above $10^{17}$ eV is a
crucial issue to solve some open questions in astrophysics such as the
acceleration and propagation mechanisms. Unfortunately, the standard procedures
to identify the primary particle of a cosmic ray shower have low efficiency
mainly due to large f... | 0703582v1 |
1993-05-11 | Electronic Structure and Bonding in Epitaxially Stabilized Cubic Iron Silicides | We present an ab initio full-potential linearized augmented plane-wave
(FLAPW) study of the structural and electronic properties of the two bulk
unstable compounds FeSi (CsCl structure) and FeSi$_2$ (CaF$_2$ structure) which
have recently been grown by molecular beam epitaxy on Si(111). We obtain
equilibrium bulk latti... | 9305007v1 |
1994-06-06 | Volume Effect in the Landau Theory of Martensitic Phase Transitions in Cubic Crystals | An effect of the volume change upon proper ferroelastic (martensitic) phase
transitions in cubic crystals is considered. Corresponding terms in the
Ginzburg-Landau expansion of the Gibbs free energy are analyzed for the first-
as well as second-order phase transitions from cubic to tetragonal lattice
under the action o... | 9406030v2 |
1995-08-26 | Magnetic Properties of Epitaxial and Polycrystalline Fe/Si Multilayers | Fe/Si multilayers with antiferromagnetic interlayer coupling have been grown
via ion-beam sputtering on both glass and single-crystal substrates. High-angle
x-ray diffraction measurements show that both sets of films have narrow Fe
peaks, implying a large crystallite size and crystalline iron silicide spacer
layers. Lo... | 9508117v1 |
1995-12-18 | Soft X-ray Fluorescence Study of Buried Silicides in Antiferromagnetically Coupled Fe/Si Multilayer | Soft x-ray fluorescence spectroscopy has been employed to obtain information
about the Si-derived valence band states of Fe/Si multilayers. The valence band
spectra are quite different for films with and without antiferromagnetic
interlayer exchange coupling, demonstrating that these multilayers have
different silicide... | 9512126v1 |
1996-09-11 | Exchange Coupling Between Iron Layers Separated by BCC Copper | The exchange coupling between Fe layers separated by BCC Cu is calculated for
Fe/Cu/Fe (001) trilayers. It is shown that the coupling is basically regulated
by three extrema of the bulk BCC Cu Fermi surface. The contributions from those
extrema are all of the same order of magnitude, but that associated with the
``bell... | 9609104v1 |
1997-06-04 | Monte Carlo Simulation of Magnetization Reversal in Fe Sesquilayers on W(110) | Iron sesquilayers grown at room temperature on W(110) exhibit a pronounced
coercivity maximum near a coverage of 1.5 atomic monolayers. On lattices which
faithfully reproduce the morphology of the real films, a kinetic Ising model is
utilized to simulate the domain-wall motion. Simulations reveal that the
dynamics is d... | 9706036v2 |
1998-01-07 | Monte Carlo simulation of magnetization reversal via domain-wall motion in Fe sesquilayers on W(110) | Iron sesquilayers are ultrathin films with coverages between one and two
atomic monolayers. They consist of an almost defect-free monolayer with compact
islands of a second atomic layer on top. This variation of the film thickness
results in a strong interaction between domain walls and the island structure.
It makes t... | 9801052v1 |
1998-04-03 | First principles simulations of liquid Fe-S under Earth's core conditions | First principles electronic structure calculations, based upon density
functional theory within the generalized gradient approximation and ultra-soft
Vanderbilt pseudopotentials, have been used to simulate a liquid alloy of iron
and sulfur at Earth's core conditions. We have used a sulfur concentration of
$\approx 12 %... | 9804035v1 |
1998-05-10 | Assisted Tunneling in Ferromagnetic Junctions and Half-Metallic Oxides | Different mechanisms of spin-dependent tunneling are analyzed with respect to
their role in tunnel magnetoresistance (TMR). Microscopic calculation within a
realistic model shows that direct tunneling in iron group systems leads to
about a 30% change in resistance, which is close but lower than experimentally
observed ... | 9805114v1 |
1998-07-14 | The hematite (alpha-Fe_2 O_3) (0001) surface: evidence for domains of distinct chemistry | Using spin-density functional theory we investigated various possible
structures of the hematite (0001) surface. Depending on the ambient oxygen
partial pressure, two geometries are found to be particularly stable under
thermal equilibrium: one being terminated by iron and the other by oxygen. Both
exhibit huge surface... | 9807202v1 |
1998-08-08 | The Influence of the Bulk Density on the Intergranular Properties of YBa2Cu3-xFexOy (0<x<0.01) Ceramics | The influence of the bulk density of YBa2Cu3-xFexOy (0 < x < 0.01) ceramics
on the intergranular superconducting (SC) properties was studied using the
temperature dependence of AC magnetic susceptibility measurements. It was found
that the simultaneous variation of the sample's density and the iron impurity
concentrati... | 9808086v1 |
1998-10-28 | Interplay of Chemical Bonding and Magnetism in Fe_4N, Fe_3N, Fe_2N | Using spin density functional theory we have carried out a comparative study
of chemical bonding and magnetism in Fe_4N, Fe_3N and Fe_2N. All of these
compounds form close packed Fe lattices, while N occupies octahedral
interstitial positions. High spin fcc Fe and hypothetical FeN with rock salt
structure have been inc... | 9810383v1 |
1998-12-16 | Superconducting and Magnetic Properties of Nb/Pd_1-xFe_x/Nb Triple Layers | The superconducting and magnetic properties of Nb/Pd_1-xFe_x/Nb triple layers
with constant Nb layer thickness d_Nb=200 A and different interlayer
thicknesses are investigated. The thickness dependence of the magnetization and
of the superconducting transition temperature shows that for small iron
concentration x the P... | 9812278v1 |
1999-11-24 | Kinetics of moisture absorption in mixtures for iron foundry | The moisture absorption in granulated materials used in foundry technologies
is analyzed. The absorption process has a diffusive behavior mainly. A simple
experimental technique, in which the wet weight increment was recorded as the
experimental parameter and an analytic method with computing procedure to find
the para... | 9911400v1 |
2000-04-18 | Metallic and nonmetallic double perovskites: A case study of A$_2$FeReO$_6$ (A= Ca, Sr, Ba) | We have investigated the structure and electronic properties of ferrimagnetic
double perovskites, A2FeReO6 (A= Ca, Sr, Ba). The A=Ba phase is cubic (Fm3m)
and metallic, while the A=Ca phase is monoclinic (P21/n) and nonmetallic.
57Fe Mossbauer spectroscopy shows that iron is present mainly in the
high-spin (S=5/2) Fe... | 0004315v1 |
2000-05-05 | Analysis of Dislocation Mechanism for Melting of Elements: Pressure Dependence | In the framework of melting as a dislocation-mediated phase transition we
derive an equation for the pressure dependence of the melting temperatures of
the elements valid up to pressures of order their ambient bulk moduli. Melting
curves are calculated for Al, Mg, Ni, Pb, the iron group (Fe, Ru, Os), the
chromium group... | 0005118v1 |
2000-05-29 | Electronic and Magnetic Properties of Febr2 | Electronic and magnetic (e-m) properties of FeBr2 have been surprisingly well
described as originating from the Fe2+ ions and their fine electronic
structure. The fine electronic structure have been evaluated taking into
account the spin-orbit (s-o) coupling, crystal-field and inter-site
spin-dependent interactions. Th... | 0005502v1 |
2000-08-08 | Influence of carbon and nitrogen on electronic structure and hyperfine interactions in fcc iron-based alloys | Carbon and nitrogen austenites, modeled by Fe8N and Fe8C superstructures are
studied by full-potential LAPW method. Structure parameters, electronic and
magnetic properties as well as hyperfine interaction parameters are obtained.
Calculations prove that Fe-C austenite can be successfully modeled by ordered
Fe8C supers... | 0008129v1 |
2000-11-23 | Magnetization in Molecular Iron Rings | The organometallic ring molecules Fe_6 and Fe_10 are leading examples of a
class of nanoscopic molecular magnets, which have been of intense recent
interest both for their intrinsic magnetic properties and as candidates for the
observation of macroscopic quantum coherent phenomena. Torque magnetometry
experiments have ... | 0011403v1 |
2001-01-31 | Langevin Simulation of Thermally Activated Magnetization Reversal in Nanoscale Pillars | Numerical solutions of the Landau-Lifshitz-Gilbert micromagnetic model
incorporating thermal fluctuations and dipole-dipole interactions (calculated
by the Fast Multipole Method) are presented for systems composed of nanoscale
iron pillars of dimension 9 nm x 9 nm x 150 nm. Hysteresis loops generated
under sinusoidally... | 0101477v2 |
2001-09-28 | Density functional simulation of small Fe nanoparticles | We calculate from first principles the electronic structure, relaxation and
magnetic moments in small Fe particles, applying the numerical local orbitals
method in combination with norm-conserving pseudopotentials. The accuracy of
the method in describing elastic properties and magnetic phase diagrams is
tested by comp... | 0109540v2 |
2001-10-09 | Decay of spin-Peierls state in CuGeO3:Fe. The case of a strong disorder | Influence of doping by iron impurity on spin-Peierls state in CuGeO3 is
studied. ESR measurements for the frequency/temperature domain 60-450 GHz/
1.8-300 K and specific heat data obtained for the interval 6-20 K show that
insertion of 1% of Fe completely destroy both spin-Peierls and
antiferromagnetic orders. Damping ... | 0110177v1 |
2001-11-27 | Complementary approaches to the ab initio calculation of melting properties | Several research groups have recently reported {\em ab initio} calculations
of the melting properties of metals based on density functional theory, but
there have been unexpectedly large disagreements between results obtained by
different approaches. We analyze the relations between the two main approaches,
based on ca... | 0111510v1 |
2001-12-03 | Electron correlation effects and ferromagnetism in Iron | Electron correlation effects in Fe are analyzed using a first principles
LCAO-scheme. In our approach, we first use a local orbital DFT-LDA solution to
introduce a Hubbard Hamiltonian without fitting parameters. In a second step,
we introduce a many-body solution to this Hamiltonian using a DMF
approximation. Our analy... | 0112038v1 |
2001-12-07 | Proton Spin Relaxation Induced by Quantum Tunneling in Fe8 Molecular Nanomagnet | The spin-lattice relaxation rate $T_{1}^{-1}$ and NMR spectra of $^1$H in
single crystal molecular magnets of Fe8 have been measured down to 15 mK. The
relaxation rate $T_1^{-1}$ shows a strong temperature dependence down to 400
mK. The relaxation is well explained in terms of the thermal transition of the
iron state b... | 0112111v1 |
2002-08-01 | Magnetic shape-memory effects in La2-xSrxCuO4 crystals | The magnetic field affects the motion of electrons and the orientation of
spins in solids, but it is believed to have little impact on the crystal
structure. This common perception has been challenged recently by ferromagnetic
shape-memory alloys, where the spin-lattice coupling is so strong that
crystallographic axes ... | 0208013v1 |
2002-08-12 | Fe/V and Fe/Co (001) superlattices: growth, anisotropy, magnetisation and magnetoresistance | Some physical properties of bcc Fe/V and Fe/Co (001) superlattices are
reviewed. The dependence of the magnetic anisotropy on the in-plane strain
introduced by the lattice mismatch between Fe and V is measured and compared to
a theoretical derivation. The dependence of the magnetic anisotropy (and
saturation magnetisat... | 0208229v1 |
2002-08-22 | Spin fluctuations, electron-phonon coupling and superconductivity in near-magnetic elementary metals; Fe,Co,Ni and Pd | An investigation of possibilities for superconductivity mediated by spin
fluctuations in some elementary metals is motivated by the recent discovery of
superconductivity in the hcp high-pressure phase of iron.
The electronic structure, the electron-phonon coupling ($\lambda_{ph}$) and
the coupling due to spin-fluctua... | 0208424v1 |
2002-08-30 | Itinerant Ferromagnetism in the Periodic Anderson Model | We introduce a novel mechanism for itinerant ferromagnetism, based on a
simple two-band model. The model includes an uncorrelated and dispersive band
hybridized with a second band which is narrow and correlated. The simplest
Hamiltonian containing these ingredients is the Periodic Anderson Model (PAM).
Using quantum Mo... | 0208604v1 |
2002-11-25 | Calculation of thermal expansion coefficient of Fe/sub 3/Al with the addition of transition metal elements | The addition of transition metal elements can significantly modify physical
properties of intermetalic compounds. We studied the influence of Molybdenum
and Vanadium additives on thermal expansion coefficient (CTE) of Fe/sub 3/Al
and FeAl over the wide range of temperatures. The site preference of both
transition metal... | 0211569v1 |
2002-12-17 | Anomalous temperature dependence of the dephasing time in mesoscopic Kondo wires | We present measurements of the magnetoconductance of long and narrow quasi
one-dimensional gold wires containing magnetic iron impurities in a temperature
range extending from $15 $mK to $4.2 $K. The dephasing rate extracted from the
weak antilocalisation shows a pronounced plateau in a temperature region of
$300 $mK -... | 0212420v1 |
2003-01-22 | Tunneling splitting of magnetic levels in Fe8 detected by 1H NMR cross relaxation | Measurements of proton NMR and the spin lattice relaxation rate 1/T1 in the
octanuclear iron (III) cluster [Fe8(N3C6H15)6O2(OH)12][Br8 9H2O], in short Fe8,
have been performed at 1.5 K in a powder sample aligned along the main
anisotropy z axis, as a function of a transverse magnetic field (i.e.,
perpendicular to the m... | 0301415v1 |
2003-02-13 | Properties of superconducting MgB_2 wires: "in-situ" versus "ex-situ" reaction technique | We have fabricated a series of iron-sheathed superconducting wires prepared
by the powder-in-tube technique from (MgB_2)_{1-x}:(Mg+2B)_x initial powder
mixtures taken with different proportions, so that x varies from 0 to 1. It
turned out that "ex-situ" prepared wire (x = 0) has considerable disadvantages
compared to a... | 0302249v1 |
2003-03-07 | Macroscopic and Microscopic Investigation on the History Dependence of the Mechanical Behaviour of Powders | As an example for history dependent mechanical behaviour of cohesive powders
experiments and computer simulations of uniaxial consolidation are compared.
Some samples were precompacted transversally to the consolidation direction and
hence had a different history. The experiments were done with two carbonyl iron
powder... | 0303132v1 |
2003-05-19 | Andreev bound states in normal and ferromagnet/high-Tc superconducting tunnel junctions | Ag/BSCCO and Fe/Ag/BSCCO planar tunnel junctions were constructed in order to
study experimentally the effect of an exchange potential on the spin polarized
current transported through Andreev bound states appearing at the interface
with a superconductor with broken time reversal pairing symmetry. The zero bias
conduct... | 0305446v1 |
2003-06-11 | Electron Coherence in Mesoscopic Kondo Wires | We present measurements of the magnetoresistance of long and narrow quasi
one-dimensional gold wires containing magnetic iron impurities. The electron
phase coherence time extracted from the weak antilocalisation shows a
pronounced plateau in a temperature region of 300 mK - 800 mK, associated with
the phase breaking d... | 0306276v1 |
2003-09-17 | Iron and molybdenum valences in double-perovskite (Sr,Nd)2FeMoO6: electron-doping effect | Double perovskite, (Sr1-xNdx)2FeMoO6, was doped with electrons through
partial substitution of divalent Sr by trivalent Nd (0 < x < 0.2). The Fe
valence and the degree of B-site order were probed by 57Fe Mossbauer
spectroscopy. Replacing Sr by Nd increased the fraction of Fe and Mo atoms
occupying wrong sites, i.e. ant... | 0309394v1 |
2003-11-21 | First-principle molecular dynamics with ultrasoft pseudopotentials: parallel implementation and application to extended bio-inorganic system | We present a plane-wave ultrasoft pseudopotential implementation of
first-principle molecular dynamics, which is well suited to model large
molecular systems containing transition metal centers. We describe an efficient
strategy for parallelization that includes special features to deal with the
augmented charge in the... | 0311507v1 |
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 |
2004-04-15 | Evidence for crossed Andreev reflection in superconductor-ferromagnet hybrid structures | We have measured the non-local resistance of aluminum-iron spin-valve
structures fabricated by e-beam lithography and shadow evaporation. The sample
geometry consists of an aluminum bar with two or more ferromagnetic wires
forming point contacts to the aluminum at varying distances from each other. In
the normal state ... | 0404360v2 |
2004-04-27 | Phase Separation in Li$_x$FePO$_4$ Induced by Correlation Effects | We report on a significant failure of LDA and GGA to reproduce the phase
stability and thermodynamics of mixed-valence Li$_x$FePO$_4$ compounds.
Experimentally, Li$_x$FePO$_4$ compositions ($0 \leq x \leq 1$) are known to be
unstable and phase separate into Li FePO$_4$ and FePO$_4$. However,
first-principles calculatio... | 0404631v2 |
2004-05-02 | Spin Dynamics and Multiple Reflections in Ferromagnetic Film in Contact with Normal Metal Layers | Spin dynamics of a metallic ferromagnetic film imbedded between normal metal
layers is studied using the spin-pumping theory of Tserkovnyak et al. [Phys.
Rev. Lett. 88, 117601 (2002)]. The scattering matrix for this structure is
obtained using a spin-dependent potential with quantum well in the
ferromagnetic region. Ow... | 0405020v1 |
2004-05-06 | Theory of Metal-Insulator Transition in PrRu4P12 and PrFe4P12 | All symmetry allowed couplings between the 4f^2-electron ground state doublet
of trivalent praseodymium in PrRu4P12 and PrFe4P12 and displacements of the
phosphorus, iron or ruthenium ions are considered. Two types of displacements
can change the crystal lattice from body-centred cubic to simple orthorhombic
or to simp... | 0405127v1 |
2004-05-07 | A linear response approach to the calculation of the effective interaction parameters in the LDA+U method | In this work we reexamine the LDA+U method of Anisimov and coworkers in the
framework of a plane-wave pseudopotential approach. A simplified
rotational-invariant formulation is adopted. The calculation of the Hubbard U
entering the expression of the functional is discussed and a linear response
approach is proposed tha... | 0405160v1 |
2004-05-10 | Self-assembly of iron nanoclusters on the Fe3O4(111) superstructured surface | We report on the self-organized growth of a regular array of Fe nanoclusters
on a nanopatterned magnetite surface. Under oxidizing preparation conditions
the (111) surface of magnetite exhibits a regular superstructure with
three-fold symmetry and a 42 A periodicity. This superstructure represents an
oxygen terminated ... | 0405201v2 |
2004-06-24 | Resonant magnetic X-ray scattering spectra in SDW Cr -- ab initio study ----- | Using ab-initio band structure calculation based on the local density
approximation, Cr K-edge resonant X-ray magnetic scattering spectra are
analyzed in the spin density wave (SDW) state of chromium. We perform band
structure calculation, assuming an ideal bcc lattice structure with the lattice
constant observed at th... | 0406576v1 |
2004-09-15 | Effect of Nano Scale Fe Doping on Superconducting Properties of MgB2 | Iron is an important sheath material for fabrication of MgB2 wires. However,
the effect of Fe doping on the superconducting properties of MgB2 remains
controversial. In this work, we present results of nano-scale Fe particle
doping in to MgB2. The Fe doping experiments were performed using both bulk and
thin film form.... | 0409408v1 |
2004-10-17 | Low-temperature anomaly in heat capacity due to overlapping the spectrums in molecular crystals | Investigations of dynamic and thermodynamic properties for a molecular
crystal tris-hexafluoroacetylacetonate-iron $Fe(O_2C_5HF_6)_3$ are presented.
Heat capacity $C_p(T)$ has been measured by adiabatic calorimetry method in the
temperature range $4.8-321 K$. An anomaly with a maximum at $T_c = 44.6 K$ has
been discove... | 0410428v1 |
2004-11-27 | Point defect dynamics in bcc metals | We present an analysis of the time evolution of self-interstitial atom and
vacancy (point defect) populations in pure bcc metals under constant
irradiation flux conditions. Mean-field rate equations are developed in
parallel to a kinetic Monte Carlo (kMC) model. When only considering the
elementary processes of defect ... | 0411680v1 |
2004-12-23 | Modeling truncated hemoglobin vibrational dynamics | We present a study on the near equilibrium dynamics of two small proteins in
the family of truncated hemoglobins, developed under the framework of a
Gaussian network approach. Effective beta carbon atoms are taken into account
besides C-alphas for all residues but glycines in the coarse-graining
procedure, without lead... | 0412661v2 |
2005-02-23 | Charge order in Fe2OBO3: An LSDA+U study | Charge ordering in the low-temperature monoclinic structure of iron oxoborate
(Fe2OBO3) is investigated using the local spin density approximation (LSDA)+U
method. While the difference between t_{2g} minority occupancies of Fe^{2+} and
Fe^{3+} cations is large and gives direct evidence for charge ordering, the
static "... | 0502555v1 |
2005-03-07 | Thermal enhancement of the antiferromagnetic exchange coupling between Fe epilayers separated by a crystalline ZnSe spacer | We have put into evidence the existence of an antiferromagnetic coupling
between iron epilayers separated by a ZnSe crystalline semiconductor. The
effect has been observed for ZnSe spacers thinner than 4 nm at
room-temperature. The coupling constant increases linearly with temperature
with a constant slope of ~5.5x 10-... | 0503148v1 |
2005-03-14 | Gutzwiller-Correlated Wave Functions: Application to Ferromagnetic Nickel | Ferromagnetic Nickel is the most celebrated iron group metal with pronounced
discrepancies between the experimental electronic properties and predictions of
density functional theories. In this work, we show in detail that the recently
developed multi-band Gutzwiller theory provides a very good description of the
quasi... | 0503332v1 |
2005-03-15 | Direct evidence of the orbital contribution to the magnetic moment in AA'FeReO6 double perovskites | Spin and orbital magnetic moments of Re in AA'FeReO6 double perovskites (A,A'
= Ba, Sr, Ca) have been directly probed employing XMCD spectroscopy at the Re
L2,3-edges. A considerable orbital magnetic moment is observed in all the
studied compounds despite octahedral coordination. Relative orbital to spin
contribution p... | 0503358v1 |
2005-04-13 | Growth Mechanisms and Oxidation-Resistance of Gold-Coated Iron Nanoparticles | We report the chemical synthesis of Fe-core/Au-shell nanoparticles by a
reverse micelle method, and the investigation of their growth mechanisms and
oxidation-resistant characteristics. The core-shell structure and the presence
of the Fe & Au phases have been confirmed by transmission electron microscopy,
energy disper... | 0504314v1 |
2005-04-26 | Theoretical estimates for proton-NMR spin-lattice relaxation rates of heterometallic spin rings | Heterometallic molecular chromium wheels are fascinating new magnetic
materials. We reexamine the available experimental susceptibility data on MCr7
wheels in terms of a simple isotropic Heisenberg Hamiltonian for M=Fe, Ni, Cu,
and Zn and find in that FeCr7 needs to be described with an iron-chromium
exchange that is d... | 0504658v2 |
2005-07-06 | Partially ferromagnetic electromagnet for trapping and cooling neutral atoms to quantum degeneracy | We have developed a compact partially ferromagnetic electromagnet to produce
a Ioffe-Pritchard trap for neutral atoms. Our structure permits strong magnetic
confinement with low power consumption. Compared to the previous iron-core
electromagnet, it allows for easy compensation of remnant fields and very high
stability... | 0507129v2 |
2005-08-19 | Spin-waves in antiferromagnetic single crystal LiFePO$_4$ | Spin-wave dispersions in the antiferromagnetic state of single crystal
LiFePO$_4$ were determined by inelastic neutron scattering measurements. The
dispersion curves measured from the (010) reflection along both {\it a}$^\ast$
and {\it b}$^\ast$ reciprocal-space directions reflect the anisotropic coupling
of the layere... | 0508480v1 |
2005-08-27 | Raman spectroscopy and field emission measurements on catalytically grown carbon nanotubes | We used microcontact printing to pattern a silicon surface with an
iron-containing catalytic solution. Multi-wall carbon nanotubes were
subsequently grown on the patterned areas by chemical vapor deposition at
temperatures between 650 and 1000C. We demonstrate that the diameter of the
catalytically grown multi-wall nan... | 0508657v2 |
2005-09-14 | Magnetic ordering in trigonal chain compounds | We present electronic structure calculations for the one-dimensional magnetic
chain compounds Ca_3CoRhO_6 and Ca_3FeRhO_6. The calculations are based on
density functional theory and the local density approximation. We use the
augmented spherical wave (ASW) method. The observed alternation of low- and
high-spin states ... | 0509374v1 |
2005-10-27 | High spin polarization in the ferromagnetic filled skutterudites KFe4Sb12 and NaFe4Sb12 | The spin polarization of ferromagnetic alkali-metal iron antimonides KFe4Sb12
and NaFe4Sb12 is studied by point-contact Andreev reflection using
superconducting Nb and Pb tips. From these measurements an intrinsic transport
spin polarization Pt of 67% and 60% for the K and Na compound, respectively, is
inferred which e... | 0510736v1 |
2005-11-21 | Electronic structure study by means of X-ray spectroscopy and theoretical calculations of the "ferric star" single molecule magnet | The electronic structure of the single molecule magnet system
M[Fe(L)2]3*4CHCl3 (M=Fe,Cr; L=CH3N(CH2CH2O)2) has been studied using X-ray
photoelectron spectroscopy, X-ray absorption spectroscopy, soft X-ray emission
spectroscopy, and density functional calculations. There is good agreement
between theoretical calculati... | 0511522v2 |
2006-02-08 | Investigation of the presence of charge order in magnetite by measurement of the spin wave spectrum | Inelastic neutron scattering results on magnetite (Fe3O4) show a large
splitting in the acoustic spin wave branch, producing a 7 meV gap midway to the
Brillouin zone boundary at q = (0,0,1/2) and E = 43 meV. The splitting occurs
below the Verwey transition temperature, where a metal-insulator transition
occurs simultan... | 0602214v1 |
2006-02-15 | A spin triplet supercurrent through the half-metallic ferromagnet CrO2 | In general, conventional superconductivity should not occur in a ferromagnet,
though it has been seen in iron under pressure. Moreover, theory predicts that
the current is always carried by pairs of electrons in a spin singlet state, so
conventional superconductivity decays very rapidly when in contact with a
ferromagn... | 0602359v1 |
2006-02-16 | Ferromagnetic resonance in systems with competing uniaxial and cubic anisotropies | We develop a model for ferromagnetic resonance in systems with competing
uniaxial and cubic anisotropies. This model applies to (i) magnetic materials
with both uniaxial and cubic anisotropies, and (ii) magnetic nanoparticles with
effective core and surface anisotropies; We numerically compute the resonance
frequency a... | 0602369v3 |
2006-02-18 | Scaling Behavior of Portevin-Le Chatelier Effect | The scaling behavior of the Portevin-Le Chatelier (PLC) effect is studied by
deforming a substitutional alloy, Al-2.5%Mg and an interstitial alloy, low
carbon steel (0.15%C, 0.33%Mn, 0.04%P, 0.05%S, 0.15%Si and rest Iron) at room
temperature for a wide range of strain rates. To reveal the exact scaling
nature, the time... | 0602436v1 |
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