publicationDate
stringlengths
1
2.79k
title
stringlengths
1
36.5k
abstract
stringlengths
1
37.3k
id
stringlengths
9
47
2012-04-18
Fe-rich border of miscibility gap and activation energy of phase decomposition in a Fe-Cr alloy
Concentration of Cr in the Fe-rich alpha-phase, x, resulted from a phase decomposition caused by an isothermal annealing at T = 415 and 450 C of a non-irradiated (NR) Fe-Cr14 EFDA sample and that of a He-ions irradiated (IR) one annealed at 415 C was determined with M\"ossbauer spectroscopy. The x-value in the latter w...
1204.4002v2
2012-05-11
Antisite traps and metastable defects in Cu(In,Ga)Se2 thin-film solar cells studied by screened-exchange hybrid density functional theory
Electronic structure calculations within screened-exchange hybrid density functional theory show that Cu(In,Ga) antisites in both CuInSe2 and CuGaSe2 are localized hole traps, which can be attributed to the experimentally observed N2 level. In contrast, GaCu antisites and their defect complexes with copper vacancies ex...
1205.2556v1
2012-05-18
Controlling exchange coupling strength in NixCu100-x thin films
Thickness (dF) and concentration (x) dependence of the Curie temperature of NixCu100-x(dF) ferromagnetic alloy layers (x =0.55,0.65, dF =[3nm{\div}12nm]) being in contact with a vanadium layer was studied. The Curie temperature of the ferromagnetic layers depends on the thickness when it is comparable with the interfac...
1205.4149v1
2012-05-18
An Effective Method to Estimate Composition Amplitude of Spinodal Decomposition for Atom Probe Tomography Validated by Phase Field Simulations
Reasonable evaluation of composition amplitude in spinodal decomposition is a challenge to microanalysis of atom probe tomography, especially at early stages when phase separation is not prominent. This impedes quantitative analysis of spinodal structure in atom probe tomography as well as comparison with simulated res...
1205.4195v1
2012-05-31
High-pressure study of non-Fermi liquid and spin-glass-like behavior in CeRhSn
We present measurements of the temperature dependence of electrical resistivity of CeRhSn up to ~ 27 kbar. At low temperatures, the electrical resistivity varies linearly with temperature for all pressures, indicating non-Fermi liquid behavior. Below a temperature Tf ~ 6 K, the electrical resistivity deviates from a li...
1205.6997v1
2012-06-11
Elastic, thermodynamic, electronic and optical properties of U2Ti
An investigation of U2Ti, a potentially safe and heavy metal-based storage material for radioactive tritium for fusion reactor, has been performed using pseudopotential density functional theory. The analysis of the elastic constants and other moduli calculated for the first time shows large anisotropy on elasticity an...
1206.2160v2
2012-06-10
Constitutive behavior of as-cast A356
The constitutive behavior of aluminum alloy A356 in the as-cast condition has been characterized using compression tests performed over a wide range of deformation temperatures (30-500{\deg}C) and strain rates (\approx0.1-10 /s). This work is intended to support the development of process models for a wide range of con...
1206.2344v1
2012-06-13
Atomic Effective Pseudopotentials for Semiconductors
We derive an analytic connection between the screened self-consistent effective potential from density functional theory (DFT) and atomic effective pseudopotentials (AEPs). The motivation to derive AEPs is to address structures with thousands to hundred thousand atoms, as given in most nanostructures. The use of AEPs a...
1206.2813v1
2012-06-13
A High Power Density, High Efficiency Hydrogen-Chlorine Regenerative Fuel Cell with a Low Precious Metal Content Catalyst
We report the performance of a hydrogen-chlorine electrochemical cell with a chlorine electrode employing a low precious metal content alloy oxide electrocatalyst for the chlorine electrode: (Ru_0.09Co_0.91)_3O_4. The cell employs a commercial hydrogen fuel cell electrode and transports protons through a Nafion membran...
1206.2883v1
2012-06-15
Tuning the metamagnetism of an antiferromagnetic metal
We describe a `disordered local moment' (DLM) first-principles electronic structure theory which demonstrates that tricritical metamagnetism can arise in an antiferromagnetic metal due to the dependence of local moment interactions on the magnetisation state. Itinerant electrons can therefore play a defining role in me...
1206.3394v1
2012-06-19
High-fidelity simulations of CdTe vapor deposition from a new bond-order potential-based molecular dynamics method
CdTe has been a special semiconductor for constructing the lowest-cost solar cells and the CdTe-based Cd1-xZnxTe alloy has been the leading semiconductor for radiation detection applications. The performance currently achieved for the materials, however, is still far below the theoretical expectations. This is because ...
1206.4231v1
2012-06-21
Electronic and optical spectra in a diluted magnetic semiconductor multilayer
The effects of random distribution of magnetic impurities with concentration $x$ in a semiconductor alloy multilayer at a paramagnetic temperature are investigated by means of coherent potential approximation and tight-binding model. The change in the electronic states and the optical absorption spectrum with $x$ is ca...
1206.4963v1
2012-06-29
Ferromagnetism and superconductivity in P-doped CeFeAsO
We report on superconductivity in CeFeAs1-xPxO and the possible coexistence with Ce- ferromagnetism (FM) in a small homogeneity range around x = 30% with ordering temperatures of T_SC = T_C = 4K. The antiferromagnetic (AFM) ordering temperature of Fe at this critical concentration is suppressed to T^N_Fe ~ 40K and does...
1206.7088v2
2012-07-09
High field magneto-transport and magnetization study of Y1-xCaxBa2Cu3O7-δ(x = 0.0-0.25)
We report DC isothermal magnetization, global critical current density (JC), Intra-grain critical current density (JCintra) and resistive upper critical field (Bc2) of polycrystalline Y1-xCaxBa2Cu3O7-{\delta} (YBCO); x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.25. Ca doping at Y sites in YBCO superconductor results in flux ...
1207.1970v2
2012-07-13
Ab Initio Discovery of Novel Crystal Structure Stability in Barium and Sodium-Calcium Compounds under Pressure using DFT
Group I/II materials exhibit unexpected structural phase transitions at high pressures, providing potential insight into the origins of elemental superconductivity. We present here a computational study of elemental barium and binary sodium-calcium alloys to identify both known and unknown phases of barium under pressu...
1207.3320v1
2012-07-16
Atomic scale investigation of Cr precipitation in copper
The early stage of the chromium precipitation in copper was analyzed at the atomic scale by Atom Probe Tomography (APT). Quantitative data about the precipitate size, 3D shape, density, composition and volume fraction were obtained in a Cu-1Cr-0.1Zr (wt.%) commercial alloy aged at 713K. Surprisingly, nanoscaled precipi...
1207.3640v1
2012-07-16
Mechanical design of ceramic beam tube braze joints for NOvA kicker magnets
The NO{\nu}A Experiment will construct a detector optimized for electron neutrino detection in the existing NuMI neutrino beam. The NuMI beam line is capable of operating at 400 kW of primary beam power and the upgrade will allow up to 700 kW. Ceramic beam tubes are utilized in numerous kicker magnets in different acce...
1207.3822v1
2012-07-16
The convergence method to calculate particles fluxes in x rays spectrometry techniques. Application in nuclear compounds
A method to calculate particle fluxes applicable in most of the spectroscopy techniques is described. Flux intensities of backscattered or absorbed electrons and emitted photons are calculated using a method of convergence to solve the Invariant Embedding equations that are used to describe the particle trajectories in...
1207.3823v1
2012-07-31
Breakdown of Stokes-Einstein relation in the supercooled liquid state of phase change materials
The application of amorphous chalcogenide alloys as data-storage media relies on their ability to undergo an extremely fast (10-100 ns) crystallisation once heated at sufficiently high temperature. However, the peculiar features that make these materials so attractive for memory devices still lack a comprehensive micro...
1207.7269v1
2012-08-01
Size Distribution and Its Scaling Behavior of InAlAs/AlGaAs Quantum Dots Grown on GaAs by Molecular Beam Epitaxy
We studied the size distribution and its scaling behavior of self-assembled InAlAs/AlGaAs quantum dots (QDs) grown on GaAs with the Stranski-Krastanov (SK) mode by molecular beam epitaxy (MBE), at both 480{\deg}C and 510{\deg}C, as a function of InAlAs coverage. A scaling function of the volume was found for the first ...
1208.0109v1
2012-08-01
First-principles study of the Mn, Al and C distribution and their effect on the stacking fault energies in austenite
We present ab-initio simulation of manganese, aluminum and carbon impurities in austenite and demonstrate their inhomogeneous distribution, which involves the repulsion of interstitial carbon atoms, the formation of bonded Mn-C pairs as well as a short range Al-ordering of D03-type. The mechanisms for the formation of ...
1208.0310v1
2012-08-07
Temperature-controlled interlayer exchange coupling in strong/weak ferromagnetic multilayers: a thermo-magnetic Curie-switch
We investigate a novel type of interlayer exchange coupling based on driving a strong/weak/strong ferromagnetic tri-layer through the Curie point of the weakly ferromagnetic spacer, with the exchange coupling between the strongly ferromagnetic outer layers that can be switched, on and off, or varied continuously in mag...
1208.1493v1
2012-08-13
Specific Heat Discontinuity DeltaC vs Tc in Annealed Ba(Fe1-xCox)2As2
The low temperature specific heat of annealed single crystal samples of Ba(Fe1-xCox)2As2 with compositions spanning the entire superconducting phase diagram was measured. Effort was made to discover the best annealing schedule to maximize Tc and minimize transition width in these samples. Values of deltaC/Tc normalized...
1208.2492v1
2012-08-28
Modulation doping to control the high-density electron gas at a polar/non-polar oxide interface
A modulation-doping approach to control the carrier density of the high-density electron gas at a prototype polar/non-polar oxide interface is presented. It is shown that the carrier density of the electron gas at a GdTiO3/SrTiO3 interface can be reduced by up to 20% from its maximum value (~ 3x10^14 cm^-2) by alloying...
1208.5711v1
2012-10-02
A first principles study of magnetism in Pd$_{3}$Fe under pressure
Recent experiments on Pd$_{3}$Fe intermetallics [Phys. Rev. Lett. 102, 237202 (2009)] have revealed that the system behaves like a classical invar alloy under high pressure. The experimental pressure-volume relation suggests an anomalous volume collapse and a substantial increase in bulk modulus around the pressure whe...
1210.0661v1
2012-10-03
A new 3D macroscopic model for shape memory alloys describing martensite reorientation
In this paper we introduce a 3D phenomenological model for shape memory behavior, accounting for: martensite reorientation, asymmetric response of the material to tension/compression, different kinetics between forward and reverse phase transformation. We combine two modeling approaches using scalar and tensorial inter...
1210.1256v1
2012-10-04
Stucture and Quality of Mono- and Bi-Component Films, Formed From Ion-Plasma Streams, Transformated During the Interaction with the Condactive Target
The essence of the method of transformation of ion-plasma streams was disclosed. A phenomenological model of binary alloy films formation was suggested, in the case of a conducting target being sputtered by ions of nongaseous substances. By example of Nb films formation and Nb-Sn system, the effect of kinetic and therm...
1210.1384v1
2012-10-04
Phase field crystal modeling of early stage precipitation and clustering
A phase field crystal model is used to investigate the mechanisms of formation and growth of early clusters in quenched/aged dilute binary alloys, a phenomenon typically outside the scope of molecular dynamics time scales. We show that formation of early sub-critical clusters is triggered by the stress relaxation effec...
1210.1501v1
2012-10-08
Sputter gas pressure effects on the properties of Sm-Co thin films deposited from a single target
We grow epitaxial Sm-Co thin films by sputter deposition from an alloy target with a nominal SmCo5 composition on Cr(100)-buffered MgO(100) single-crystal substrates. By varying the Ar gas pressure, we can change the composition of the film from a SmCo5-like to a Sm2Co7-like phase. The composition, crystal structure, m...
1210.2240v1
2012-10-22
Phase Diagram of Ferroelastic Systems in the Presence of Disorder: Analytical Model and Experimental Verification
There is little consensus on the nature of the glass state and its relationship to other strain states in ferroelastic materials which show the shape memory effect and superelasticity. We provide a thermodynamic interpretation of the known strain states, including precursory tweed and strain glass, by mapping the probl...
1210.5919v1
2012-10-29
Large magnetoelectric effect in mechanically mediated structure of TbFe2, Pb(Zr,Ti)O3 and nonmagnetic flakes
Magnetoelectric (ME) effect has been studied in a structure of a magnetostrictive TbFe2 alloy, two piezoelectric Pb(Zr,Ti)O3 (PZT) ceramics, and two nonmagnetic flakes. The ME coupling originates from the magnetic-mechanical-electric transform of the magnetostrictive effect in TbFe2 and the piezoelectric effect in PZT ...
1210.7542v1
2012-10-31
Scattering-Independent Anomalous Nernst Effect in Ferromagnets
Using the full-potential linearized augmented plane-wave method within the density functional theory, we compute all contributions to the scattering independent part of the thermoelectric conductivity tensor, namely the intrinsic contribution and the side-jump contribution. For the ferromagnetic materials bcc Fe, hcp C...
1210.8283v2
2012-11-01
Tune of Magnetism and Electronic Structures of Alkali Metal Carbides with Rocksalt Structure
Electronic structures of carbides with the rocksalt structure were calculated by full potential electronic codes solving the Kohn-Sham equation. Bonding characters were analyzed by constructing tight-binding Hamiltonian based on maximally-localized Wannier functions. It was found that the cations in these compounds act...
1211.0162v2
2012-11-01
A theoretical investigation of structural, electronic and optical properties of bulk copper nitrides
We present a detailed first-principles DFT study of the equation of state (EOS), energy-optimized geometries, phase stabilities and electronic properties of bulk crystalline Cu3N, CuN and CuN2 in a set of twenty different structural phases. We analyzed different structural preferences for these three stoichiometries an...
1211.0179v1
2012-11-01
Neutron diffraction evidence for kinetic arrest of the first-order austenite to martensite transition in Ni37Co11Mn42.5Sn9.5
Neutron diffraction measurements, performed in presence of an external magnetic field, have been used to show structural evidence for the kinetic arrest of the first-order phase transition from the high temperature austenite phase to the low temperature martensite phase in the magnetic shape memory alloy Ni37Co11Mn42.5...
1211.0238v1
2012-11-04
Impact of correlations and finite temperatures on the anomalous Hall conductivity of 3d-transition-metals
Employing the linear response Kubo formalism as implemented in a fully relativistic multiple-scattering Korringa-Kohn-Rostoker Green function method a systematic first-principles study based on density-functional theory (DFT) of the anomalous Hall conductivity (AHC) of the 3$d$-transition-metals Fe, Co and Ni is presen...
1211.0702v1
2012-11-11
Magnetic phase transitions in Gd64Sc36 studied using non-contact ultrasonics
The speed and attenuation of ultrasound propagation can be used to determine material properties and identify phase transitions. Standard ultrasonic contact techniques are not always convenient due to the necessity of using couplant, however, recently reliable non-contact ultrasonic techniques involving electromagnetic...
1211.2471v1
2012-11-12
Step Free Energies at Faceted Solid-Liquid Interfaces from Equilibrium Molecular Dynamics Simulations
In this work a method is proposed for computing step free energies for faceted solid-liquid interfaces based on atomistic simulations. The method is demonstrated in an application to (111) interfaces in elemental Si, modeled with the classical Stillinger-Weber potential. The approach makes use of an adiabatic trapping ...
1211.2732v1
2012-11-26
Momentum Dependent Local-Ansatz Wavefunction from Weak to Strong Electron Correlations
Momentum dependent local-ansatz (MLA) wavefunction describes accurately electron correlations from the weak to intermediate Coulomb interaction regimes. We point out that the MLA can describe the correlations from the weak to strong Coulomb interaction regimes by modifying the starting wavefunction from the Hartree-Foc...
1211.5881v1
2012-11-29
Phase separation of antiferromagnetic ground states in systems with imperfect nesting
We analyze the phase diagram for a system of weakly-coupled electrons having an electron- and a hole-band with imperfect nesting. Namely, both bands have spherical Fermi surfaces, but their radii are slightly different, with a mismatch proportional to the doping. Such a model is used to describe: the antiferromagnetism...
1211.6850v2
2012-11-30
Effect of thermal history on the short-range order in Fe-Cr alloys
Effect of a thermal history of Fe(100-x)Cr(x) (x < 20) samples on a Cr atoms distribution within the first (1NN) and the second (2NN) neighbor-shells was studied with the M\"ossbauer spectroscopy. The distribution was expressed in terms of the Cowley-Warren short-range order (SRO) parameters: <alpha1> for 1NN, <alpha2>...
1211.7300v1
2012-12-04
Spinodal Decomposition of Magnetic Ions in Eu-Codoped Ge/1-x/Cr/x/Te
We present the experimental evidence for the presence of spinodal decomposition of the magnetic ions in the Ge/1-x-y/Cr/x/Eu/y/Te samples with chemical composition varying in the range of 0.015 < x < 0.057 and 0.003 < y < 0.042. The ferromagnetic transition at temperatures 50 < T < 57 K was observed, independent of the...
1212.0666v1
2012-12-05
Tuning the porosity of bimetallic nanostructures by a soft templating approach
We use hexagonal mesophases made of oil-swollen surfactant-stabilized tubes arranged on a triangular lattice in water and doped with metallic salts as templates for the radiolytic synthesis of nanostructures. The nanostructures formed in this type of soft matrix are bimetallic palladium-platinum porous nanoballs compos...
1212.1064v1
2012-12-12
The Microstructure of Tool Steel after Low Temperature Ion Nitriding
The microstructural development in H13 tool steel upon nitriding by an ion beam process was investigated. The nitriding experiments were performed at a relatively low temperature of about 400\deg C and at constant ion beam energy (400 eV) of different doses in a high-vacuum preparation chamber; the ion source was fed w...
1212.2997v1
2012-12-14
Polymer Assisted Synthesis of FeNi Nanoparticles
Polymer assisted spherical FeNi nanoparticles were prepared via wet chemical method using hydrazine as a reducing agent and polymers (PVP and PEG) as reducing and stabilizing agent. Structural studies performed using XRD and TEM shows uniform dispersion of fine FeNi nanocrystallites in nanocomposite particles. The size...
1212.3566v1
2012-12-17
The first-principles study of thermodynamical properties of random magnetic overlayers on fcc-Cu(001) substrate
We present the theoretical study of thermodynamical properties of fcc-Cu(001) substrate covered by iron-cobalt monolayer as well as by incomplete iron layer. The effective two-dimensional Heisenberg Hamiltonian is constructed from first principles and properties of exchange interactions are investigated. The Curie temp...
1212.4057v1
2012-12-18
Inelastic neutron scattering study of phonon density of states in nanostructured Si1xGex thermoelectrics
Inelastic neutron scattering measurements are utilized to explore relative changes in the generalized phonon density of states of nanocrystalline Si1xGex thermoelectric materials prepared via ball milling and hot-pressing techniques. Dynamic signatures of Ge clustering can be inferred from the data by referencing the r...
1212.4431v1
2012-12-19
Theory of the spin Hall effect, and its inverse, in a ferromagnetic metal near the Curie temperature
We give a theory of the inverse spin Hall effect (ISHE) in ferromagnetic metals based on skew scattering via collective spin fluctuations. This extends Kondo's theory of the anomalous Hall effect (AHE) to include short-range spin-spin correlations. We find a relation between the ISHE and the four-spin correlations near...
1212.4561v1
2013-01-07
Positron Source Simulations for ILC 1 TeV Upgrade
The generation and capture of polarized positrons at a source with a superconducting helical undulator having 4.3 cm period and 500 GeV electron drive beam have been simulated. The positron polarization has been calculated for the different undulator K values (up to K = 2.5). Without applying a photon collimator, the m...
1301.1222v2
2013-01-09
Monoatomic magnetic interfaces in IrMn/Cr/Co thin films probed by grazing incidence X-ray absorption spectroscopy
We present depth-resolved experimental results on the atomic and electronic structures of the Co-Cr interface on four IrMn/Cr/Co thin films with variable thickness of the Cr layer. Grazing incidence X-ray absorption near edge structure near the Cr K-edge was used, and an Angstrom resolved depth-profile for this layer w...
1301.1832v1
2013-01-11
Role of Electronic Structure in the Morphotropic Phase Boundary of TbxDy1-xCo2 Studied by First-principles Calculation
Physically parallel to ferroelectric morphotropic phase boundary, a phase boundary separating two ferromagnetic phase of different crystallographic symmetries was found in TbxDy1-xCo2. High-resolution synchrotron XRD has been carried out to offer experimental evidence for TbxDy1-xCo2. It has been proved that TbxDy1-xCo...
1301.2389v2
2013-01-14
Single-Crystal Growth and Thermoelectric Properties of Ge(Bi,Sb)4Te7
The thermoelectric properties between 10 and 300 K and the growth of single crystals of n-type and p-type GeBi4Te7, GeSb4Te7, and the Ge(Bi1-xSbx)4Te7 solid solution are reported. Single crystals were grown by the modified Bridgman method, and p-type behavior was achieved by the substitution of Bi by Sb in GeBi4Te7. Th...
1301.3030v1
2013-01-22
Studies of FemIrn nano clusters using Density Functional Theory Techniques
The structure, binding energy, magnetic moments and electronic structure of FemIrn clusters are investigated using state of the art density functional theory techniques. Fully unconstrained structural relaxations are undertaken by considering all possible non equivalent cluster structures. The optimized clusters are al...
1301.5150v1
2013-02-12
Micro-alloying and the Toughness of Glasses: Modeling with Pinned Particles
The usefulness of glasses, and particularly of metallic glasses, in technological applications is often limited by their toughness, which is defined as the area under the stress vs. strain curve before plastic yielding. Recently toughness was found to increase significantly by the addition of small concentrations of fo...
1302.2858v1
2013-02-14
Formation of one-dimensional self-assembled silicon nanoribbons on Au(110)-(2x1)
We report results on the self-assembly of silicon nanoribbons on the (2x1) reconstructed Au(110) surface under ultra-high vacuum conditions. Upon adsorption of 0.2 monolayer (ML) of silicon the (2x1) reconstruction of Au(110) is replaced by an ordered surface alloy. Above this coverage a new superstructure is revealed ...
1302.3391v1
2013-02-18
Observation of large positive magnetoresistance and its sign reversal in GdRhGe
Magnetic properties, heat capacity and magnetoresistance (MR) of polycrystalline GdRhGe are investigated. It shows two antiferromagnetic transitions, one at T1=31.8 K and the other at T2=24 K, and field induced metamagnetic transition over a wide temperature range. The ac susceptibility data reveal that the transition ...
1302.4226v2
2013-02-19
Structure and Dielectric Properties of Amorphous High-kappa Oxides: HfO2, ZrO2 and their alloys
High-$\kappa$ metal oxides are a class of materials playing an increasingly important role in modern device physics and technology. Here we report theoretical investigations of the properties of structural and lattice dielectric constants of bulk amorphous metal oxides by a combined approach of classical molecular dyna...
1302.4534v1
2013-02-22
Broken Dynamic Symmetry and Phase Transition Precursor
Symmetry breaking is a central concept of Landau phase transition theory, which, however, only considers time-averaged static symmetry of crystal lattice while neglects dynamic symmetry of lattice vibrations thus fails to explain the ubiquitous transformation precursor phenomena. We show that incomplete phonon softenin...
1302.5479v1
2013-02-22
Design principles for HgTe based topological insulator devices
The topological insulator properties of CdTe/HgTe/CdTe quantum wells are theoretically studied. The CdTe/HgTe/CdTe quantum well behaves as a topological insulator beyond a critical well width dimension. It is shown that if the barrier(CdTe) and well-region(HgTe) are altered by replacing them with the alloy Cd$_{x}% $Hg...
1302.5716v1
2013-03-02
The effect of shock-wave profile on dynamic brittle failure
The influence of shock-wave-loading profile on the failure processes in a brittle material has been investigated. Tungsten heavy alloy (WHA) specimens have been subjected to two shock-wave loading profiles with a similar peak stress of 15.4 GPa but different pulse durations. Contrary to the strong dependence of strengt...
1303.0393v1
2013-03-08
Influence of symmetry on Sm magnetism studied on SmIr2Si2 polymorphs
Polycrystalline samples of SmIr2Si2 formed at room temperature both the low temperature phase (LTP) and the metastable high temperature phase (HTP), respectively, depending on the heat treatment. The samples were studied by X-ray powder diffraction, DTA, specific-heat and magnetization measurements with respect to temp...
1303.1908v1
2013-03-09
Adiabatic transformation as a search tool for new topological insulators: distorted ternary Li$_2$AgSb-class semiconductors and related compounds
We demonstrate that first-principles based adiabatic continuation approach is a very powerful and efficient tool for constructing topological phase diagrams and locating non-trivial topological insulator materials. Using this technique, we predict that the ternary intermetallic series Li$_2M'X$ where $M'$=Cu, Ag, Au, o...
1303.2228v1
2013-03-15
Tunable optoelectronic and ferroelectric properties in Sc-based III-nitrides
Sc-based III-nitride alloys were studied using Density Functional Theory with special quasi-random structures and were found to retain wide band gaps which stay direct up to x = 0.125 (ScxAl1-xN) and x = 0.375 (ScxGa1-xN). Epitaxial strain stabilization prevents spinodal decomposition up to x = 0.3 (ScxAl1-xN on GaN) a...
1303.3745v1
2013-03-15
Thermoelectric Properties of Polycrystalline NiSi3P4
The Hall and Seebeck coefficients, electrical resistivity and thermal conductivity of polycrystalline NiSi3P4 were characterized from 2 to 775K. Undoped NiSi3P4 behaves like a narrow gap semiconductor, with activated electrical resistivity \rho below room temperature and a large Seebeck coefficient of ~400uV/K at 300K....
1303.3772v1
2013-03-23
Yb Valence Change in (Ce,Yb)CoIn5 from spectroscopy and bulk properties
The electronic structure of (Ce,Yb)CoIn5 has been studied by a combination of photoemission, x-ray absorption and bulk property measurements. Previous findings of a Ce valence near 3+ for all x and of an Yb valence near 2.3+ for x>0.3 were confirmed. One new result of this study is that the Yb valence for x<0.2 increas...
1303.5871v2
2013-03-29
Giant magnetocaloric effect in isostructural MnNiGe-CoNiGe system by establishing a Curie-temperature window
An effective scheme of isostructural alloying was applied to establish a Curie-temperature window in isostructural MnNiGe-CoNiGe system. With the simultaneous accomplishment of decreasing structural-transition temperature and converting antiferromagnetic martensite to ferromagnetic state, a 200 K Curie-temperature wind...
1303.7282v1
2013-04-01
Surface States of Topological Crystalline Insulators in IV-VI Semiconductors
Topological crystalline insulators (TCI) are new topological phases of matter protected by crystal symmetry of solids. Recently, the first realization of TCI has been predicted and observed in IV-VI semiconductor SnTe and related alloys Pb_{1-x}Sn_{x}(Te, Se). By combining k.p theory and band structure calculation, we ...
1304.0430v1
2013-04-04
The effect of Al doping on the structure and magnetism in cobaltite CaBaCo4O7
We report the effects of Al-doping on the structure and magnetic properties in CaBa(Co$_{1-x}$Al$_{x}$)$_4$O$_7$ (0$\leq$x$\leq$0.25). The system exhibits a structural transition from an orthorhombic symmetry to a hexagonal symmetry when the Al content exceeds $x =$ 0.1. The Curie temperature and the value of the magne...
1304.1387v1
2013-04-05
Band offset of GaAs/AlxGa1-xAs heterojunctions from atomistic first principles
Using an atomistic first principles approach, we investigate the band offset of the GaAs/AlxGa1-xAs heterojunctions for the entire range of the Al doping concentration 0<x<=1. We apply the coherent potential approach to handle the configuration average of Al doping and a recently proposed semi-local exchange potential ...
1304.1686v1
2013-04-06
Effect of activation procedure on Sm-Co-Fe-Zr-B compound for low temperature efficient hydrogen storage
The present research work is focused on the effect of activation procedure on the hydrogen absorption-desorption properties of new rare earth transition metal compound based on Sm(Co0.6Fe0.2Zr0.16B0.04)7.5 composition. Crystal structure and composition is always connected to the maximum capacity of the intermetallic hy...
1304.1901v1
2013-04-08
Effects of alloying and strain on the magnetic properties of Fe$_{16}$N$_2$
The electronic structure and magnetic properties of pure and doped {Fe$_{16}$N$_2$} systems have been studied in the local-density (LDA) and quasiparticle self-consistent {\emph{GW}} approximations. The {\emph{GW}} magnetic moment of pure {Fe$_{16}$N$_2$} is somewhat larger compared to LDA but not anomalously large. Th...
1304.2428v2
2013-04-10
Advanced holographic nondestructive testing system for residual stress analysis
The design and operating of a portable holographic interferometer for residual stress analysis by creating a small scratch along with a new mathematical algorithm of calculations are discussed. Preliminary data of the stress investigations on aluminum and steel alloys have been obtained by the automatic processing of t...
1304.3141v1
2013-04-19
Effects of composition and chemical disorder on the magnetocrystalline anisotropy of Fe_{x}Pt_{1-x} alloys
We perform first principles calculations of the magnetocrystalline anisotropy energy (MAE) of the L1_{0}-like Fe_{x}Pt_{1-x} samples studied experimentally by Barmak and co-workers in [J. Appl. Phys. 98 (2005) 033904]. The variation of composition and long-range chemical order in the samples was studied in terms of the...
1304.5323v1
2013-04-30
Pressure-induced Topological Phase Transitions in Rock-salt Chalcogenides
By means of a comprehensive theoretical investigation, we show that external pressure can induce topological phase transitions in IV-VI semiconducting chalcogenides with rock-salt structure. These materials satisfy mirror symmetries that are needed to sustain topologically protected surface states, at variance with tim...
1304.7931v1
2013-04-30
Non-trivial spin-texture of the coaxial Dirac cones on the surface of topological crystalline insulator SnTe
We present first principles calculations of the nontrivial surface states and their spin-textures in the topological crystalline insulator SnTe. The surface state dispersion on the [001] surface exhibits four Dirac-cones centered along the intersection of the mirror plane and the surface plane. We propose a simple mode...
1304.8119v1
2013-05-05
Computational studies of the glass-forming ability of model bulk metallic glasses
Bulk metallic glasses (BMGs) are produced by rapidly thermally quenching supercooled liquid metal alloys below the glass transition temperature at rates much faster than the critical cooling rate R_c below which crystallization occurs. The glass-forming ability of BMGs increases with decreasing R_c, and thus good glass...
1305.0971v1
2013-05-15
Elastic scattering of surface states on three-dimensional topological insulators
Topological insulators as new type of quantum matter materials are characterized by a full insulating gap in the bulk and gapless edge/surface states which are protected by time-reversal symmetry. We propose the interference patterns caused by elastic scattering of defects or impurities are dominated by surface states ...
1305.3369v1
2013-05-15
Integration and characterization of solid wall electrodes in microfluidic devices fabricated in a single photolithography step
We describe the fabrication and characterization of solid 3-dimensional electrodes in direct contact with microfluidic channels, implemented using a single photolithography step, allowing operation in high-dielectric constant media. Incorporation and self-alignment of electrodes is achieved by combining microsolidic ap...
1305.3554v1
2013-05-27
A Rigidity Result for a Reduced Model of a Cubic-to-Orthorhombic Phase Transition in the Geometrically Linear Theory of Elasticity
We study a simplified two-dimensional model for a cubic-to-orthorhombic phase transition occuring in certain shape-memory-alloys. In the low temperature regime the linear theory of elasticity predicts various possible patterns of martensite arrangements: Apart from the well known laminates this phase transition display...
1305.6200v1
2013-05-31
Quasiparticle Interference on the Surface of Topological Crystalline Insulator Pb(1-x)Sn(x)Se
Topological crystalline insulators represent a novel topological phase of matter in which the surface states are protected by discrete point group-symmetries of the underlying lattice. Rock-salt lead-tin-selenide alloy is one possible realization of this phase which undergoes a topological phase transition upon changin...
1306.0043v2
2013-06-04
AC vs. DC Electrophoretic Deposition of Hydroxyapatite on Titanium
The bio-inertness of titanium and its alloys attracts their use as bone implants. However a bioactive coating is usually necessary for improving the bone bonding of such implants. In this study, electrophoretic deposition(EPD) of hydroxyapatite (HA) powder on titanium plate was performed using butanol as solvent under ...
1306.0743v1
2013-06-10
Transient and self-limited nanostructures on patterned surfaces
Site-controlled quantum dots formed during the deposition of (Al)GaAs layers by metalorganic vapor-phase epitaxy on GaAs(111)B substrates patterned with inverted pyramids result in geometric and compositional self-ordering along the vertical axis of the template. We describe a theoretical scheme that reproduces the exp...
1306.2161v1
2013-06-18
Magnetic-Moment Fragmentation and Monopole Crystallization
The Coulomb phase, with its dipolar correlations and pinch-point-scattering patterns, is central to discussions of geometrically frustrated systems, from water ice to binary and mixed-valence alloys, as well as numerous examples of frustrated magnets. The emergent Coulomb phase of lattice-based systems has been associa...
1306.4120v2
2013-06-18
Momentum Dependent Local-Ansatz with Hybrid Wavefunction from Weak to Strong Electron Correlations
The variational theory of momentum dependent local-ansatz (MLA) has been generalized by introducing a hybrid (HB) wavefunction as a starting wavefunction, whose potential can flexibly change from the Hartree-Fock type to the alloy-analogy type by varying a weighting factor from zero to one. Numerical results based on t...
1306.4123v1
2013-06-21
Germanium crystals on silicon show their light
Germanium and silicon-germanium alloys have found entry into Si technology thanks to their compatibility with Si processing and their ability to tailor electronic properties by strain and band-gap engineering. Germanium's potential to extend Si functionalities, as exemplified by lasing action of strained-Ge on Si subst...
1306.5270v1
2013-06-25
Thermomechanical design of a static gas target for electron accelerators
Gas targets are often used at accelerator facilities. A design of high-pressure gas cells that are suitable for hydrogen and helium isotopes at relatively high electron beam currents is presented. In particular, we consider rare gas targets, $^3$H$_2$ and $^3$He. In the design, heat transfer and mechanical integrity of...
1306.6000v1
2013-06-27
Amorphous GdFeCo Films Exhibiting Large and Tunable Perpendicular Magnetic Anisotropy
We report the compositional and temperature dependence of magnetic compensation in amorphous GdFeCo films. Magnetic compensation is attributed to the competition between antiferromagnetic coupling of rare-earth with transition-metal (TM) ions and ferromagnetic interaction between the TM ions. The low-Gd region from 20 ...
1306.6451v1
2013-06-27
Finding the Rashba-type spin-splitting from interband scattering in quasiparticle interference maps
We have studied the BiCu$_2$/Cu(111) surface alloy using low-temperature scanning tunneling microscopy and spectroscopy. We observed standing waves caused by scattering off defects and step edges. Different from previous studies on similar Rashba-type surfaces, we identified multiple scattering vectors that originate f...
1306.6662v1
2013-07-04
First-principles study of Co concentration and interfacial resonance states in Fe$_{1-x}$Co$_x$ magnetic tunnel junctions
The optimal Co concentration in Fe$_{1-x}$Co$_{x}$/MgO magnetic tunnel junctions (MTJs) that maximizes tunneling magnetoresistance (TMR) is still under investigation. We perform a first-principles transport study on MTJs using disordered electrodes modeled using the virtual crystal approximation (VCA) and ordered alloy...
1307.1374v1
2013-07-09
Complex order-parameter phase-field models derived from structural phase-field-crystal models
The phase-field-crystal (PFC) modeling paradigm is rapidly emerging as the model of choice when investigating materials phenomena with atomistic scale effects over diffusive time scales. Recent variants of the PFC model, so-called structural PFC (XPFC) models introduced by Greenwood et al., have further increased the c...
1307.2620v1
2013-07-20
Magnetic properties of Sn/1-x/Cr/x/Te diluted magnetic semiconductors
We present the studies of Sn/1-x/Cr/x/Te semimagnetic semiconductors with chemical composition x ranging from 0.004 to 0.012. The structural characterization indicates that even at low average Cr-content x < ?0.012, the aggregation into micrometer size clusters appears in our samples. The magnetic properties are affect...
1307.5464v1
2013-07-21
Influence of excitation frequency on Raman modes of In1-xGaxN thin films
Low energy optical modes of MBE-grown In1-xGaxN thin films with different values of x are investigated using Raman spectroscopy. We also studied the influence of Raman excitation frequency using red and green lasers on scattering intensity of various Raman modes. For those In1-xGaxN alloys whose bandgap energy is close...
1307.5545v1
2013-07-23
Impact of cation-based localized electronic states on the conduction and valence band structure of AlInN alloys
We demonstrate that cation-related localized states strongly perturb the band structure of $\text{Al}_{1-x}\text{In}_x$N leading to a strong band gap bowing at low In content. Our first-principles calculations show that In-related localized states are formed both in the conduction and the valence band in $\text{Al}_{1-...
1307.5985v2
2013-07-25
Memory Effect and Triplet Pairing Generation in the Superconducting Exchange Biased Co/CoOx/Cu41Ni59/Nb/Cu41Ni59 Layered Heterostructure
We fabricated a nanolayered hybrid superconductor-ferromagnet spin-valve structure, the resistive state of which depends on the preceding magnetic field polarity. The effect is based on a strong exchange bias (about -2 kOe) on a diluted ferromagnetic copper-nickel alloy and generation of a long range odd in frequency t...
1307.6742v1
2013-07-29
Hydrogen accommodation in Zr second phase particles: Implications for H pick-up and hydriding of Zircaloy-2 and Zircaloy-4
Ab-initio computer simulations have been used to predict the energies associated with the accommodation of H atoms at interstitial sites in {\alpha}, {\beta}-Zr and Zr.M intermetallics formed with common alloying additions (M = Cr, Fe, Ni). Intermetallics that relate to the Zr2(Ni,Fe) second phase particles (SPPs) foun...
1307.7616v1
2013-08-05
Controlling the Polarity of the Transient Ferromagnetic-Like State in Ferrimagnets
After the application of an ultrashort laser pulse, the antiferromagnetic alignment in rare earth-transition metal alloys can temporarily become ferromagnetic with the rare-earth polarity. Proposed models merely describe this effect, without showing the route for its manipulation. Here we use extensive atomistic spin...
1308.0993v2
2013-08-06
Strain engineering of topological properties in lead-salt semiconductors
Rock-salt chalcogenide SnTe represents the simplest realization of a topological insulator where a crystal symmetry allows for the appearence of topologically protected metallic states with an even number of Dirac cones on high-symmetry crystal surfaces. Related rock-salt lead chalcogenides have been predicted as well ...
1308.1288v1
2013-08-06
Novel types of anti-ecloud surfaces
In high power RF devices for space, secondary electron emission appears as the main parameter governing the multipactor effect and as well as the e-cloud in large accelerators. Critical experimental activities included development of coatings with low secondary electron emission yield (SEY) for steel (large accelerator...
1308.1316v1
2013-08-12
Formation of Nickel-Platinum Silicides on a Silicon Substrate: Structure, Phase Stability, and Diffusion from Ab initio Computations
The formation of Ni(Pt)silicides on a Si(001) surface is investigated using an ab initio approach. After deposition of a Ni overlayer alloyed with Pt, the calculations reveal fast diffusion of Ni atoms into the Si lattice, which leads initially to the formation of Ni2Si. At the same time Si atoms are found to diffuse i...
1308.2605v1
2013-08-13
Strain effects on the electronic structure of the FeSe0.5Te0.5 superconductor
The electronic structure of the strained FeSe0.5Te0.5 superconductor has been investigated from first principles. Our calculation results indicate that the influence of hydrostatic, biaxial or uniaxial compressive stress on the density of states at the Fermi level is insignificant. The overall shape of the Fermi-surfac...
1308.2949v1