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2009-09-02
Surface energies of stoichiometric FePt and CoPt alloys and their implications for nanoparticle morphologies
We have calculated surface energies and surface magnetic order of various low-indexed surfaces of monoatomic Fe, Co, and Pt, and binary, ordered FePt, CoPt, and MnPt using density functional theory. Our results for the binary systems indicate that elemental, Pt-covered surfaces are preferred over Fe- and Co-covered and...
0909.0420v2
2009-09-29
A model for shape memory alloys with the possibility of voids
The paper is devoted to the study of a mathematical model for the thermomechanical evolution of metallic shape memory alloys. The main novelty of our approach consists in the fact that we include the possibility for these materials to exhibit voids during the phase change process. Indeed, in the engineering paper has b...
0909.5286v1
2009-10-27
Pressure-induced phonon-freezing in the ZnBeSe alloy: a study via the percolation mesoscope
We use the 1-bond -> 2-phonon percolation doublet of zincblende alloys as a mesoscope for an unusual insight into their phonon behavior under pressure. We focus on (Zn,Be)Se and show by Raman scattering that the original Be-Se doublet at ambient pressure, of the stretching-bending type, turns into a pure-bending single...
0910.5175v2
2009-10-31
Compensation temperature of 3d mixed ferro-ferrimagnetic ternary alloy
In this study, we have considered the three dimensional mixed ferro-ferrimagnetic ternary alloy model of the type AB$_{p}$C$_{1-p}$ where the A and X (X=B or C) ions are alternately connected and have different Ising spins S$^{A}$=3/2, S$^{B}$=1 and S$^{C}$=5/2, respectively. We have investigated the dependence of the ...
0911.0078v1
2009-11-23
The Geometry of Slow Structural Fluctuations in a Supercooled Binary Alloy
The liquid structure of a glass-forming binary alloy is studied using molecular dynamics simulations. The analysis combines common neighbour analysis with the geometrical approach of Frank and Kasper to establish that the supercooled liquid contains extended clusters characterised by the same short range order as the c...
0911.4509v1
2009-11-24
An Equation of State for Anisotropic Solids under Shock Loading
An anisotropic equation of state is proposed for accurate extrapolation of high-pressure shock Hugoniot states to other thermodynamics states for shocked single crystals and polycrystalline alloys. The proposed equation of state represents mathematical and physical generalization of the Mie-Gr\"{u}neisen equation of st...
0911.4717v2
2009-12-01
A common magnetic origin for the Invar effects in fcc iron-based ferromagnets
Using first-principles calculations, in conjunction with Ising magnetism, we undertake a theoretical study to elucidate the origin of the experimentally observed Invar effects in disordered fcc iron-based ferromagnets. First, we show that our theory can account for the Invar effects in iron-nickel alloys, the anomalies...
0912.0215v4
2009-12-11
Model for solute diffusion during rapid solidification of binary alloy in semi-infinite volume
On the basis of local nonequilibrium approach, the one-dimensional model of the solute diffusion during rapid solidification of the binary alloy in the semi-infinite volume is considered. Within the scope of the model it is supposed that mass transport is described by the telegrapher equation. The basic assumption conc...
0912.2309v4
2010-01-08
Vibrational properties of alpha- and sigma-phase Fe-Cr alloy
Experimental investigation as well as theoretical calculations, of the Fe-partial phonon density-of-states (DOS) for nominally Fe_52.5Cr_47.5 alloy having (a) alpha- and (b) sigma-phase structure were carried out. The former at sector 3-ID of the Advanced Photon Source, using the method of nuclear resonant inelastic X-...
1001.1211v1
2010-01-12
Optical absorption spectrum in disordered semiconductor multilayers
The effects of chemical disorder on the electronic and optical properties of semiconductor alloy multilayers are studied based on the tight-binding theory and single-site coherent potential approximation. Due to the quantum confinement of the system, the electronic spectrum breaks into a set of subbands and the electro...
1001.2000v3
2010-01-27
An anomalous butterfly-shaped magnetoresistance loop in an alloy, Tb4LuSi3
Magnetic-field (H) induced first-order magnetic transition and the assiciated electronic phase-separation phenomena are active topics of research in magnetism. Magnetoresistance (MR) is a key property to probe these phenomena and, in literature, a butterfly-shaped MR loop has been noted while cycling the field, with th...
1001.4942v1
2010-02-08
Spacing Characterization in Al-Cu Alloys Directionally Solidified Under Transient Growth Conditions
We study spacing selection in directional solidification of Al-Cu alloys under transient growth conditions. New experimental results are presented which reveal that dendritic spacing versus solidification rate evolves in an almost step-wise fashion, consistent with previous theoretical predictions of Langer and co-work...
1002.1699v1
2010-02-12
\textit{Ab initio} study of interacting lattice vibrations and stabilization of the $β$-phase in Ni-Ti shape-memory alloy
Lattice dynamical methods used to predict phase-transformations in crystals typically evaluate the harmonic phonon spectra and therefore do not work in frequent and important situations where the crystal structure is unstable in the harmonic approximation, such as the $\beta$ structure when it appears as a high-tempera...
1002.2482v2
2010-03-02
Vacancy-tuned paramagnetic/ferromagnetic martensitic transformation in Mn-poor Mn_{1-x}CoGe alloys
It is shown that a temperature window between the Curie temperatures of martensite and austenite phases around the room temperature can be obtained by a vacancy-tuning strategy in Mn-poor Mn1-xCoGe alloys (0 <= x <= 0.050). Based on this, a martensitic transformation from paramagnetic austenite to ferromagnetic martens...
1003.0489v3
2010-03-03
On the Debye temperature in sigma-phase Fe-V alloys
A series of sigma-phase Fe_{100-x}V_x samples with 34.4 < x < 59.0 were investigated by neutron and X-ray diffraction and Mossbauer spectroscopy (MS) techniques. The first two methods were used for verification of the transformation from alpha to sigma phase and they also permitted to determine lattice parameters of th...
1003.0811v1
2010-03-10
Force-matched embedded-atom method potential for niobium
Large-scale simulations of plastic deformation and phase transformations in alloys require reliable classical interatomic potentials. We construct an embedded-atom method potential for niobium as the first step in alloy potential development. Optimization of the potential parameters to a well-converged set of density-f...
1003.2210v2
2010-03-22
Dissociative adsorption of methane on surface oxide structures of Pd-Pt alloys
The dissociative adsorption of methane on variously oxidized Pd, Pt and Pd-Pt surfaces is investigated using density-functional theory, as a step towards understanding the combustion of methane on these materials. For Pd-Pt alloys, models of surface oxide structures are built on the basis of known oxides on Pd and Pt. ...
1003.4114v1
2010-04-07
Indium-Gallium Segregation in CuIn$_{x}$Ga$_{1-x}$Se$_2$: An ab initio based Monte Carlo Study
Thin-film solar cells with CuIn$_x$Ga$_{1-x}$Se$_2$ (CIGS) absorber are still far below their efficiency limit, although lab cells reach already 19.9%. One important aspect is the homogeneity of the alloy. Large-scale simulations combining Monte Carlo and density functional calculations show that two phases coexist in ...
1004.1080v1
2010-04-21
Effects of Spin Fluctuations and Anomalous Thermal Expansion of delta-Plutonium
We suggest a model for the magnetic dynamics of - plutonium and its alloys in order to show that the dynamical fluctuations of the magnetization density, or spin fluctuations, may be responsible for the anomalies of their observed thermal expansion. We show that due to strong magneto-elastic coupling, spin fluctuations...
1004.3658v1
2010-05-07
Tuning independently Fermi energy and spin splitting in Rashba systems: Ternary surface alloys on Ag(111)
By detailed first-principles calculations we show that the Fermi energy and the Rashba splitting in disordered ternary surface alloys (BiPbSb)/Ag(111) can be independently tuned by choosing the concentrations of Bi and Pb. The findings are explained by three fundamental mechanisms, namely the relaxation of the adatoms,...
1005.1162v1
2010-06-21
Signatures of a quantum Griffiths phase in a d-metal alloy close to its ferromagnetic quantum critical point
We report magnetization ($M$) measurements close to the ferromagnetic quantum phase transition of the d-metal alloy Ni$_{1-x}$V$_x$ at a vanadium concentration of $x_c \approx 11.4 %$. In the diluted regime ($x>x_c$), the temperature ($T$) and magnetic field ($H$) dependencies of the magnetization are characterized by ...
1006.4094v2
2010-07-03
Reentrant behavior of superconducting alloys
A dirty BCS superconductor with magnetic impurities is studied. Asymptotic solution of the thermodynamics of such superconductor with spin $1/2$ and $7/2$ magnetic impurities, is found. To this end, the system's free energy $f(H, \beta)$ is bounded from above and below by mean-field type bounds, which are shown to coal...
1007.0476v1
2010-08-17
Spin projection and spin current density within relativistic electronic transport calculations
A spin projection scheme is presented which allows the decomposition of the electric conductivity into two different spin channels within fully relativistic $ab$ $initio$ transport calculations that account for the impact of spin-orbit coupling. This is demonstrated by calculations of the spin-resolved conductivity of ...
1008.2900v1
2010-08-27
Optical orientation and spin-dependent recombination in GaAsN alloys under continuous-wave pumping
We present a systematic theoretical study of spin-dependent recombination and its effect on optical orientation of photoelectron spins in semiconductors with deep paramagnetic centers. For this aim we generalize the Shockley-Read theory of recombination of electrons and holes through the deep centers with allowance for...
1008.4755v1
2010-09-14
Impact of gamma' particle coarsening on the critical resolved shear stress of nickel-base superalloys with low aluminium and/or titanium content
In Ni-base superalloys with low Al and/or Ti content the precipitation and subsequent coarsening of gamma' particles at intermediate temperatures contribute to the degradation of the mechanical properties of the alloy. In the present paper the coarsening process is modelled and the change of the critical resolved shear...
1009.2676v1
2010-09-16
The rise of spin-flip transitions in the anomalous Hall effect of FePt alloy
We carry out first-principles calculations which demonstrate the importance of spin-flip transitions for the intrinsic anomalous Hall conductivity of ordered FePt alloys. We show the such transitions get enhanced by large spin-orbit coupling of Pt atoms, becoming negligible when Pt is replaced by lighter isoelectronic ...
1009.3184v1
2010-09-24
Surface-directed spinodal decomposition in the pseudobinary alloy (HfO_2)_x(SiO_2)_{1-x}
Hf silicate films (HfO_2)_{0.25}(SiO_2)_{0.75} with thicknesses in the range 4-20 nm were grown on silicon substrate by atomic layer deposition at 350 deg.C.The Hf distributions in as-grown and 800 deg.C annealed films were investigated by high resolution transmission electron microscopy (HRTEM), angle-resolved x-ray p...
1009.4946v1
2010-09-30
Temperature Dependence of the Dynamics of Portevin-Le Chatelier Effect in Al-2.5%Mg alloy
Tensile tests were carried out by deforming polycrystalline samples of Al-2.5%Mg alloy at four different temperatures in an intermediate strain rate regime of 2x10-4s-1 to 2x10-3s-1. The Portevin-Le Chatelier (PLC) effect was observed throughout the strain rate and temperature region. The mean cumulative stress drop ma...
1009.6043v1
2010-10-01
Nanocrystalline Zr3Al Made through Amorphization by Repeated Cold Rolling and Followed by Crystallization
The intermetallic compound Zr3Al is severely deformed by the method of repeated cold rolling. By X-ray diffraction it is shown that this leads to amorphization. TEM investigations reveal that a homogeneously distributed debris of very small nanocrystals is present in the amorphous matrix that is not resolved by X-ray d...
1010.0190v1
2010-10-06
Multiband tight-binding theory of disordered ABC semiconductor quantum dots: Application to the optical properties of alloyed CdZnSe nanocrystals
Zero-dimensional nanocrystals, as obtained by chemical synthesis, offer a broad range of applications, as their spectrum and thus their excitation gap can be tailored by variation of their size. Additionally, nanocrystals of the type ABC can be realized by alloying of two pure compound semiconductor materials AC and BC...
1010.1168v1
2010-10-26
Short-Range Order in Fe-Rich Fe-Cr Alloys as Revealed by Mössbauer Spectroscopy
Distribution of Cr atoms in Fe_{100-x}Cr_x alloys with x \le 25 within the first two coordination shells, 1NN-2NN, around probe 57Fe atoms was studied by means of the M\"ossbauer Spectroscopy. Clear evidence was found that the distribution is characteristic of a given atomic configuration. Only the configurations with ...
1010.5352v2
2010-11-01
Optimal and hysteretic fluxes in alloy solidification: Variational principles and chimney spacing
We take a numerical approach to analyze the mechanisms controlling the spacing of chimneys -- channels devoid of solid -- in two-dimensional mushy layers formed by solidifying a binary alloy. Chimneys are the principal conduits through which buoyancy effects transport material out of the mushy layer and into the liquid...
1011.1223v1
2010-11-17
Oxidation resistance of graphene-coated Cu and Cu/Ni alloy
The ability to protect refined metals from reactive environments is vital to many industrial and academic applications. Current solutions, however, typically introduce several negative effects, including increased thickness and changes in the metal physical properties. In this paper, we demonstrate for the first time t...
1011.3875v1
2010-12-04
Study of magnetic alloy cores for HIRFL-CSRm compressor cavity
For selecting the properly magnetic alloy (MA) material to load the RF compression cavity, the measurement of the MA cores which is produced by Liyuan Company has been carried out at IMP. We measured 4 kinds of MA core materials, type V1, V2, A1 and A2. And we mainly focus on the permeability, quality factor (Q value) ...
1012.0897v1
2010-12-15
Complex magnetic behavior and high spin polarization in Fe(3-x)Mn(x)Si alloys
Fe3Si is a ferromagnetic material with possible applications in magnetic tunnel junctions. When doped with Mn, the material shows a complex magnetic behavior, as suggested by older experiments. We employed the Korringa-Kohn-Rostoker (KKR) Green function method within density-functional theory (DFT) in order to study th...
1012.3463v1
2010-12-22
A scalable parallel Monte Carlo algorithm for atomistic simulations of precipitation in alloys
We present an extension of the semi-grandcanonical (SGC) ensemble that we refer to as the variance-constrained semi-grandcanonical (VC-SGC) ensemble. It allows for transmutation Monte Carlo simulations of multicomponent systems in multiphase regions of the phase diagram and lends itself to scalable simulations on massi...
1012.5082v2
2010-12-25
Scattering effect in proton beam windows at spallation targets
Proton beam window (PBW) is a boundary wall between a high vacuum area in the proton beam line and the helium atmosphere in a helium vessel at a high beam power target. The thermal and mechanical problems of the PBW have been studied in other spallation neutron sources; however, the scattering effect in PBW is seldom r...
1012.5460v2
2011-01-11
Transport and magnetic behavior under pressure and high-resolution photoemission studies of Ce2Rh(o.7)Co(0.3)Si3, an alloy on the verge of quantum critical point
We report the influence of external pressure on the temperature dependence of magnetization and electrical resistivity as well as high-resolution photoemission studies for an alloy, Ce2Rh(0.7)Co(0.3)Si3, ordering magnetically below 3 K. It is found that the external pressure has the same effect as that induced by (furt...
1101.2012v1
2011-02-09
Suppression of time reversal symmetry breaking superconductivity in Pr(Os,Ru)_4Sb_12 and (Pr,La)Os_4Sb_12
Zero-field muon spin relaxation experiments have been carried out in the Pr(Os_{1-x}Ru_x)_4Sb_12 and Pr_{1-y}La_yOs_4Sb_12 alloy systems to investigate broken time-reversal symmetry (TRS) in the superconducting state, signaled by the onset of a spontaneous static local magnetic field B_s. In both alloy series B_s initi...
1102.1997v1
2011-02-16
The role of spin-flip transitions in the anomalous Hall effect of FePt alloy
We carry out first-principles calculations which demonstrate the importance of the non-spin-conserving part of the spin-orbit interaction for the intrinsic anomalous Hall conductivity of ordered FePt alloys. The impact of this interaction is strongly reduced if Pt is replaced by the lighter isoelectronic element Pd. An...
1102.3376v1
2011-02-28
Charge transfer on the metallic atom pair bond, and the crystal structures adopted by intermetallic compounds
Pauling had proposed that charge is transferred from the more electronegative atom to the less electronegative one during metallic alloying. An expression has recently been derived for the energy of the unlike atom-pair bond using that concept. In this paper, Pauling's view is further supported by showing that the elec...
1102.5655v1
2011-03-01
The investigation of YAlO3-NdAlO3 system, synthesis and characterization
The binary phase diagram of the YAlO3 (YAP) - NdAlO3 (NAP) system was determined by differential thermal analysis (DTA) and X-ray powder diffraction (XRD) measurements. High purity nanocrystalline powders and small single crystals of Y_{1-x}Nd_{x}AlO_3 (0 \leq x \leq 1) have been produced successfully by modified sol-g...
1103.0180v2
2011-03-02
Reversible attachment of platinum alloy nanoparticles to non-functionalized carbon nanotubes
The formation of monodisperse, tunable sized, alloyed nanoparticles of Ni, Co, or Fe with Pt and pure Pt nanoparticles attached to carbon nanotubes has been investigated. Following homogeneous nucleation, nanoparticles attach directly to non-functionalized singlewall and multiwall carbon nanotubes during nanoparticle s...
1103.0496v1
2011-04-20
Bandgap engineering of Cd1-xSrxO
Structural, electronic and optical properties of Cd1-xSrxO (0 \leq x \leq 1) are calculated for the first time using density functional theory. Our results show that these properties are strongly dependent on x. The bond between Cd and O is partially covalent and the covalent nature of the bond decreases as the concent...
1104.4085v1
2011-05-30
Dislocation Driven Chromium Precipitation in Fe-9Cr Binary Alloy: A Positron Lifetime Study
The influence of initial heat treatment on anomalous Cr precipitation within high temperature solubility region in Fe-9Cr alloy has been investigated using positron lifetime studies. Air-quenched samples with pre-existing dislocations exhibited a distinct annealing stage in positron lifetime between 800 and 1100 K corr...
1105.5880v2
2011-06-08
Relating field-induced shift in transition temperature to the kinetics of coexisting phases in magnetic shape memory alloys
In a magnetic shape memory alloy system, we vary composition following phenomenological arguments to tune macroscopic properties. We achieve significantly higher shift in austenite to martensitic phase transition temperature with magnetic field. This enhancement is accompanied by significant broadening of the transitio...
1106.1532v1
2011-07-11
The Inner Crust and its Structure
In this chapter we discuss some possible physical pictures that describe the constitution of the inner crust of compact objects. Different relativistic models both with constant couplings and density dependent ones are used. We calculate the liquid-gas phase transition in asymmetric nuclear matter from the thermodynami...
1107.2099v3
2011-07-13
The MOLDY short-range molecular dynamics package
We describe a parallelised version of the MOLDY molecular dynamics program. This Fortran code is aimed at systems which may be described by short-range potentials and specifically those which may be addressed with the embedded atom method. This includes a wide range of transition metals and alloys. MOLDY provides a ran...
1107.2619v1
2011-07-29
A macroscale, phase-field model for shape memory alloys with non-isothermal effects: influence of strain-rate and environmental conditions on the mechanical response
A Ginzburg-Landau model for the macroscopic behaviour of a shape memory alloy is proposed. The model is one-dimensional in essence, in that we consider the effect of the martensitic phase transition in terms of a uniaxial deformation along a fixed direction and we use a scalar order parameter whose equilibrium values d...
1107.5998v1
2011-08-11
Ordering in ternary nitride semiconducting alloys
We present a thorough theoretical study of ordering phenomena in nitride ternary alloys GaInN, AlInN, and AlGaN. Using the Monte Carlo approach and energetics based on the Keating model we analyze the influence of various factors on ordering in bulk crystals and epitaxial layers. We characterize the degree of both shor...
1108.2447v2
2011-08-15
Nanostructured Melt-Spun Sm(Co,Fe,Zr,B)7:5 Alloys for High-Temperature Magnets
High coercivity, the highest for Cu-free 2 : 17 Sm-Co ribbons, has been obtained in as-spun (= 211 kOe) and short time annealed (= 232 kOe) samples of Sm(CobalFe Zr B)7 5 alloys, with varying B, Zr, and Fe content (= 0-0 06, = 0-0 16, = 0 08-0 3) and wheel speed. In as-spun samples, the TbCu7 type structure and in anne...
1108.2988v1
2011-08-15
With no Color and Scent: Nanoflowers of Metals and Alloys
Ordered volume submicron surface structures "nanoflowers" - are obtained while growing metal nanowires in porous membranes by means of pulsed current electroplating. These structures occur if the electroplating is continued after the nanowires appear on the membrane surface. Various ordered Ag, Pb, PdNi and PbIn volume...
1108.4589v1
2011-09-26
Electronic Transport in Metallic Systems and Generalized Kinetic Equations
This paper reviews some selected approaches to the description of transport properties, mainly electroconductivity, in crystalline and disordered metallic systems. A detailed qualitative theoretical formulation of the electron transport processes in metallic systems within a model approach is given. Generalized kinetic...
1109.5532v1
2011-10-03
Tri-critical point and suppression of the Shastry-Sutherland phase in Ce$_{2}$Pd$_{2}$Sn by Ni doping
Structural, magnetization and heat capacity measurements were performed on Ce$_2$(Pd$_{1-x}$Ni$_x$)$_2$Sn ($0 \leq x \leq 0.25$) alloys, covering the full range of the Mo$_2$FeB$_2$ structure stability. In this system, the two transitions observed in Ce$_2$Pd$_2$Sn (at $T_N=4.8$\,K and $T_C=2.1$\,K respectively) conver...
1110.0426v1
2011-10-14
Formation of Microcrystalline Structure in Large-Scale Ingots of Ti Alloy Ti-6Al-4V during the Complex Loading
A new method of combined loading was developed for manufacturing large - scale ingot of alpha-beta titanium alloy Ti-6Al-4V with the diameter of the gauge 120 mm and the length 300 mm. The process includes torsion with simultaneous tensile deformation, followed by a single compression and drawing of the ingot in alpha-...
1110.3122v1
2011-10-18
Higher-order contributions to the Rashba-Bychkov effect with application to Bi/Ag(111) surface alloy
In order to explain the anisotropic Rashba-Bychkov effect observed in several metallic surface-state systems, we use k.p perturbation theory with a simple group-theoretical analysis and construct effective Rashba Hamiltonians for different point groups up to third order in the wavenumber. We perform relativistic ab ini...
1110.3953v1
2011-11-06
Chemically-Mediated quantum criticality in NbFe_2
Laves-phase Nb{1+c}Fe_{2-c} is a rare itinerant intermetallic compound exhibiting magnetic quantum criticality at c_{cr}=1.5%Nb excess; its origin, and how alloying mediates it, remains an enigma. For NbFe_2, we show that an unconventional band critical point (uBCP) above the Fermi level E_F explains most observations,...
1111.1399v1
2011-11-28
Evolution of a metastable phase with a magnetic phase coexistence phenomenon and its unusual sensitivity to magnetic field cycling in the alloys Tb5-xLuxSi3 (x <= 0.7)
Recently, we reported an anomalous enhancement of the positive magnetoresistance beyond a critical magnetic field in Tb5Si3 in the magnetically ordered state, attributable to 'inverse metamagnetism'. This results in unusual magnetic hysteresis loops for the pressurized specimens, which are relevant to the topic of 'ele...
1111.6368v1
2012-01-05
Search for quantum criticality in a ferromagnetic system UNi1-xCoxSi2
Polycrystalline samples of the isostructural alloys UNi1-xCoxSi2 (0 <= x <= 1) were studied by means of x-ray powder diffraction, magnetization, electrical resistivity and specific heat measurements, at temperatures down to 2 K and in magnetic fields up to 5 T. The experimental data revealed an evolution from strongly ...
1201.1075v1
2012-01-05
Nucleation and growth of the γ' (AlAg2) precipitate in Al-Ag(-Cu) alloys
Precipitation of the \gamma' (AlAg2) phase was investigated in Al-Ag(-Cu) alloys using high resolution transmission electron microscopy and scanning transmission electron microscopy. Precipitation commenced with segregation of silver to stacking faults, followed by thickening in steps corresponding to single unit cell ...
1201.1325v1
2012-01-19
Impact of microstructure, temperature and strain ratio on energy-based low- cycle fatigue life prediction models for TiAl alloys
In this paper, two fatigue lifetime prediction models are tested on TiAl intermetallic using results from uniaxial low-cycle fatigue tests. Both assessments are based on dissipated energy but one of them considers a hydrostatic pressure correction. This work allows to confirm, on this kind of material, the linear natur...
1201.4084v1
2012-02-04
Si3AlP: A new promising material for solar cell absorber
First-principles calculations are performed to study the structural and optoelectronic properties of the newly synthesized nonisovalent and lattice-matched (Si2)0.6(AlP)0.4 alloy [T. Watkins et al., J. Am. Chem. Soc. 2011, 133, 16212.] We find that the ordered CC-Si3AlP with a basic unit of one P atom surrounded by thr...
1202.0879v1
2012-02-06
Simulation of the shape memory effect in a NiTi nano model system
The shape memory behavior of a NiTi nanoparticle is analyzed by molecular dynamics simulations. After a detailed description of the equilibrium structures of the used model potential, the multi variant martensitic ground state, which depends on the geometry of the particle, is discussed. Tensile load is applied, changi...
1202.1078v1
2012-02-21
A first-principles investigation on the effects of magnetism on the Bain transformation of $α$-phase FeNi systems
The effects of magnetism on the Bain transformation of $\alpha$-phase FeNi systems are investigated by using the full potential linearized augmented plane wave (FLAPW) method based on the generalized gradient approximation (GGA). We found that Ni impurity in bcc Fe increases the lattice constant in ferromagnetic (FM) s...
1202.4726v1
2012-02-21
Band gap tuning in ferroelectric Bi4Ti3O12 by alloying LaTMO3 (TM = Ti, V, Cr, Mn, Co, Ni, and Al)
We fabricated ferroelectric Bi4Ti3O12 (BiT) single crystalline thin films site-specifically substituted with LaTMO3 (TM = Al, Ti, V, Cr, Mn, Co, and Ni) on SrTiO3 substrates by pulsed laser epitaxy. When transition metals are incorporated into a certain site of the BiT, some of BiT-LaTMO3 showed a substantially decreas...
1202.4786v1
2012-02-25
Effects of configurational disorder on adatom mobilities on TiAlN(001) surfaces
We use metastable NaCl-structure Ti0.5Al0.5N alloys to probe effects of configurational disorder on adatom surface diffusion dynamics which control phase stability and nanostructural evolution during film growth. First-principles calculations were employed to obtain potential energy maps of Ti and Al adsorption on an o...
1202.5645v1
2012-03-03
Hybrid expansions for local structural relaxations
A model is constructed in which pair potentials are combined with the cluster expansion method in order to better describe the energetics of structurally relaxed substitutional alloys. The effect of structural relaxations away from the ideal crystal positions, and the effect of ordering is described by interatomic-dist...
1203.0626v1
2012-04-18
Effect of magnetism on the lattice dynamics in the sigma-phase Fe-Cr alloys
Anomalies in the temperature dependences of the recoil-free factor, f, and the average center shift, <CS>, measured by 57-Fe Mossbauer Spectroscopy, were observed for the first time in the archetype of the \sigma-phase alloys system, Fe-Cr. In both cases the anomaly started at the temperature close to the magnetic orde...
1204.4067v1
2012-04-23
The role of phase compatibility in martensite
Shape memory alloys inherit their macroscopic properties from their mesoscale microstructure originated from the martensitic phase transformation. In a cubic to orthorhombic transition, a single variant of marten- site can have a compatible (exact) interface with the austenite for some special lattice parameters in con...
1204.5208v1
2012-06-11
Sigma-phase in the Fe-Re alloy system: experimental and theoretical studies
X-ray diffraction (XRD) and M\"ossbauer spectroscopy techniques combined with theoretical calculations based on the Korringa-Kohn-Rostoker (KKR) electronic structure calculation method were used to investigate \sigma-phase Fe_{100-x}Re_{x} alloys (x = 43, 45, 47, 49 and 53). Structural data such as site occupancies and...
1206.2377v1
2012-07-04
Silver segregation to θ' (Al2Cu)-Al interfaces in Al-Cu-Ag alloys
\theta' (Al2Cu) precipitates in Al-Cu-Ag alloys were examined using high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The precipitates nucleated on dislocation loops on which assemblies of {\gamma}' (AlAg2) precipitates were present. These dislocation loops were enriched in silver pr...
1207.0897v1
2012-07-14
Magnetoelectric Interactions in Layered Composites of Piezoelectric Quartz and Magnetostrictive Alloys
Mechanical strain mediated magnetoelectric effects are studied in bilayers and trilayers of piezoelectric quartz and magnetostrictive permendur (P), an alloy of Fe-Co-V. It is shown that the magneto-electric voltage coefficient (MEVC), proportional to the ratio of the piezoelectric coupling coefficient to the permittiv...
1207.3411v2
2012-07-14
Topological phase transition induced by random substitution
The transition from topologically nontrivial to a trivial state is studied by first-principles calculations on bulk zinc-blende type (Hg$_{1-x}$Zn$_x$)(Te$_{1-x}$S$_x$) disordered alloy series. The random chemical disorder was treated by means of the Coherent Potential Approximation. We found that although the phase tr...
1207.3463v1
2012-07-26
Spin-orbit-coupling induced domain-wall resistance in diffusive ferromagnets
We investigate diffusive transport through a number of domain wall (DW) profiles of the important magnetic alloy Permalloy taking into account simultaneously noncollinearity, alloy disorder, and spin-orbit coupling fully quantum mechanically, from first principles. In addition to observing the known effects of magnetiz...
1207.6277v2
2012-07-30
Thermoelectric properties of Pr3Rh4Sn13-type Yb3Co4Ge13 and Yb3Co4Sn13 compounds
Crystallographic data and thermoelectric properties (from 240 K up to 380 K) of Yb3Co4Ge13, Yb3Co4Sn13 compounds and Yb2CeCo4Ge13 and Yb2.3La0.7Co4Ge13 solid solutions are reported. The Seebeck coefficients, electric resistance and thermal conductivity increase monotonically with increasing temperature from 240 to 380 ...
1207.6875v2
2012-08-30
Giant Spin Hall Effect Induced by Skew Scattering from Bismuth Impurities inside Thin Film CuBi Alloys
We demonstrate that a giant spin Hall effect (SHE) can be induced by introducing a small amount of Bi impurities in Cu. Our analysis based on a new 3-dimensional finite element treatment of spin transport shows that the sign of the SHE induced by the Bi impurities is negative and its spin Hall (SH) angle amounts to -0....
1208.6208v2
2012-08-31
Band engineering in dilute nitride and bismide semiconductor lasers
Highly mismatched semiconductor alloys such as GaNAs and GaBiAs have several novel electronic properties, including a rapid reduction in energy gap with increasing x and also, for GaBiAs, a strong increase in spin orbit- splitting energy with increasing Bi composition. We review here the electronic structure of such al...
1208.6441v1
2012-10-11
Optical orientation of nuclei in nitrogen alloys GaAsN at room temperature
The intensity and the giant circular polarization of edge luminescence in a longitudinal magnetic field have been measured in nitrogen alloys GaAsN under circularly polarized pumping. It has been found that these dependences are shifted with respect to zero field by a value Beff. The magnitude of the internal field Bef...
1210.3302v1
2012-10-19
Non-collinear magnetic ordering in compressed FePd$_3$ ordered alloy: a first principles study
By means of ab initio calculations based on the density functional theory we investigated magnetic phase diagram of ordered FePd$_3$ alloy as a function of external pressure. Considering several magnetic configurations we concluded that the system under pressure has a tendency to non-collinear spin alignment. Analysi...
1210.5478v2
2012-10-24
Magnetic phase diagram of CePt3B1-xSix
We present a study of the main bulk properties (susceptibility, magnetization, resistivity and specific heat) of CePt_3B_(1-x)Si-x, an alloying system that crystallizes in a noncentrosymmetric lattice, and derive the magnetic phase diagram. The materials at the end point of the alloying series have previously been stud...
1210.6489v3
2012-11-05
Phase-decomposition-related short-range ordering in a Fe-Cr alloy
A redistribution of Cr atoms related to a phase decomposition (PD) caused by an isothermal annealing at 415 C in a 15.15 at%Cr Fe-Cr alloy was studied in an ex-situ way by the conversion electrons M\"ossbauer spectroscopy. Analysis of the spectra in terms of a two-shell model enabled determination of probabilities of 1...
1211.0857v2
2012-11-14
Direct ab-initio molecular dynamic study of ultrafast phase change in Ag-alloyed Ge$_{2}$Sb$_{2}$Te$_{5}$
We employed ab-initio molecular dynamics to directly simulate the effects of Ag alloying ($\sim5%$ Ag concentration) on the phase change properties of Ge$_{2}$Sb$_{2}$Te$_{5}$. The short range order is preserved, whereas a slight improvement in the chemical order is observed. A slight decrease in the fraction of tetrah...
1211.3383v1
2012-12-03
Measurement of the thermal expansion coefficient of an Al-Mg alloy at ultra-low temperatures
We describe a result coming from an experiment based on an Al-Mg alloy (~ 5% Mg) suspended bar hit by an electron beam and operated above and below the termperature of transition from superconducting to normal state of the material. The amplitude of the bar first longitudinal mode of oscillation, excited by the beam in...
1212.0368v2
2013-01-23
Comparative study of tight-binding and ab initio electronic structure calculations focused on magnetic anisotropy in ordered CoPt alloy
An empirical multiorbital (spd) tight binding (TB) model including magnetism and spin-orbit coupling is applied to calculations of magnetic anisotropy energy (MAE) in CoPt L1_0 structure. A realistic Slater-Koster parametrisation for single-element transition metals is adapted for the ordered binary alloy. Spin magneti...
1301.5369v1
2013-01-28
Structural and magnetic properties of Pr-alloyed MnBi nanostructures
The structural and magnetic properties of Pr-alloyed MnBi (short MnBi-Pr) nanostructures with a range of Pr concentrations have been investigated. The nanostructures include thin films having Pr concentrations 0, 2, 3, 5 and 9 atomic percent and melt-spun ribbons having Pr concentrations 0, 2, 4 and 6 percent respectiv...
1301.6782v1
2013-02-13
Magnetism and Verwey transition in magnetite nanoparticles in thin polymer film
Magnetic and structural properties of magnetite nanoparticles stabilized in polyvinyl-alcohol thin films are investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) and static magnetometry techniques. The nanoparticles have well-defined crystallinity,...
1302.3090v1
2013-02-15
Continuous melting and thermal-history-dependent freezing in the confined Na-K eutectic alloy
23Na NMR studies of the Na-K eutectic alloy embedded into porous glass with 7 nm pores showed that melting of Na2K confined nanoparticles is a continuous process with smooth changes in the Knight shift of a narrow resonance line and nuclear spin relaxation between those in the crystalline and liquid states. The interme...
1302.3871v1
2013-02-28
The high strain-rate behaviour of three molecular weights of polyethylene examined with a magnesium alloy split-Hopkinson pressure bar
A traditional split-Hopkinson pressure bar system has been modified by the addition of ZK60A magnesium alloy pressure bars in order to increase the resolution of data when examining specimens of low-density, high-density and ultra-high molecular weight polyethylene. It was found that the low density of the ZK60A allowe...
1302.7225v1
2013-03-25
Ab initio studies of the tunneling magneto-Seebeck effect: influence of magnetic material
We found a strong influence of the composition of the magnetic material on the temperature dependence of the tunneling magneto-Seebeck effect in $MgO$ based tunnel junctions. We use \textit{ab initio} alloy theory to consider different $Fe_xCo_{1-x}$ alloys for the ferromagnetic layer. Even a small change of the compos...
1303.6330v1
2013-04-16
Ab initio study of the alloying effect of transition metals on structure, stability and ductility of CrN
The alloying effect on the lattice parameters, isostructural mixing enthalpies and ductility of the ternary nitride systems Cr1-xTMxN (TM=Sc, Y; Ti, Zr, Hf; V, Nb, Ta; Mo, W) in the cubic B1 structure has been investigated using first-principles calculations. Maximum mixing enthalpy due to large lattice mismatch in Cr1...
1304.4584v1
2013-04-24
Low temperature ferromagnetism, surface paramagnetism and exchange bias effect in nano-grained alpha-Fe1.4Ga0.6O3 oxide
The compound alpha-Fe1.4Ga0.6O3 has been prepared by mechanical alloying of alpha-Fe2O3 and Ga2O3 and subsequent heating of the mechanical alloyed samples in vacuum condition. Magnetic ordering of alpha-Fe2O3 has been modified by substitution of non-magnetic Ga atoms. The ferromagnetism in alpha-Fe1.4Ga0.6O3 is more so...
1304.6512v1
2013-04-29
Hybrid Monte Carlo/molecular dynamics simulation of a refractory metal high entropy alloy
The high entropy alloy containing refractory metals Mo-Nb-Ta-W has a body centered cubic structure, which is not surprising given the complete mutual solubility in BCC solid solutions of all pairs of the constituent elements. However, first principles total energy calculations for the binaries reveal a set of distinct ...
1304.7800v2
2013-05-10
Implementation of non-equilibrium vertex corrections in KKR: transport through disordered layers
The theoretical description of modern nanoelectronic devices requires a quantum mechanical treatment and often involves disorder, e.g. form alloys. Therefore, the ab initio theory of transport using non-equilibrium Green's functions is extended to the case of disorder described by the coherent potential approximation. ...
1305.2399v1
2013-05-23
Electronic origin of the orthorhombic Cmca structure in compressed elements and binary alloys
Formation of the complex structure with 16 atoms in the orthorhombic cell, space group Cmca (Pearson symbol oC16) was experimentally found under high pressure in the alkali elements (K, Rb, Cs) and polyvalent elements of groups IV (Si, Ge) and V (Bi). Intermetallic phases with this structure form under pressure in bina...
1305.5341v1
2013-05-24
From magnetic to Fermi Liquid behavior in CeCo{1-x}Fe{x}Si alloys
Structural, magnetic and thermal measurements performed on CeCo{1-x}Fe{x}Si alloys are reported. Three regions can be recognized: i) Co-rich (x < 0.20) with a decreasing long range antiferromagnetic order which vanishes at finite temperature, ii) an intermediate region (0.20 < x < 0.30) showing a broad magnetic anomaly...
1305.5717v1
2013-06-03
A first-principles linear response description of the spin Nernst effect
A first-principles description of the spin Nernst effect, denoting the occurrence of a transverse spin current due to a temperature gradient, is presented. The approach, based on an extension to the Kubo-Streda equation for spin transport, supplies in particular the formal basis for investigations of diluted as well as...
1306.0621v2
2013-06-27
Influence of the magnetic material on tunneling magnetoresistance and spin-transfer torque in tunnel junctions: Ab initio studies
The dependence of tunneling magnetoresistance and spin-transfer torque in FeCo/MgO/FeCo tunnel junctions on the Co concentration and the bias voltage are investigated ab initio. We find that the tunneling magnetoresistance decreases with the Co concentration in contradiction with previous calculations but in agreement ...
1306.6447v1
2013-07-05
Existence of solutions for a mathematical model related to solid-solid phase transitions in shape memory alloys
We consider a strongly nonlinear PDE system describing solid-solid phase transitions in shape memory alloys. The system accounts for the evolution of an order parameter (related to different symmetries of the crystal lattice in the phase configurations), of the stress (and the displacement), and of the absolute tempera...
1307.1572v1
2013-07-23
Mechanism of uniaxial magnetocrystalline anisotropy in transition metal alloys
Magnetocrystalline anisotropy in transition metal alloys (FePt, CoPt, FePd, MnAl, MnGa, and FeCo) was studied using first-principles calculations to elucidate its specific mechanism. The tight-binding linear muffin-tin orbital method in the local spin-density approximation was employed to calculate the electronic struc...
1307.5961v2
2013-07-24
Nature of the glassy magnetic state in Cu$_{2.84}$Mn$_{0.44}$Al$_{0.72}$ shape memory alloy
The magnetic ground state of the ferromagnetic shape memory alloy of nominal composition Cu$_{2.84}$Mn$_{0.44}$Al$_{0.72}$ was investigated. The sample shows reentry of a glassy magnetic phase below the martensitic transition temperature, which is found to have complex character with two distinct anomalies in the tempe...
1307.6310v1