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2023-06-09
Finite-temperature second-order perturbation analysis of magnetocrystalline anisotropy energy of L10-type ordered alloys
We present a novel finite-temperature second-order perturbation method incorporating spin-orbit coupling to investigate the temperature-dependent site-resolved contributions to the magnetocrystalline anisotropy energy (MAE), specifically K1(T), in FePt, MnAl, and FeNi alloys. Our developed method successfully reproduce...
2306.05681v1
2023-07-11
Slip intermittency and dwell fatigue in titanium alloys: a discrete dislocation plasticity analysis
Slip intermittency and stress oscillations in titanium alloy Ti-7Al-O that were observed using in-situ far-field high energy X-ray diffraction microscopy (ff-HEDM) are investigated using a discrete dislocation plasticity (DDP) model. The mechanistic foundation of slip intermittency and stress oscillations are shown to ...
2307.05316v1
2023-08-11
Observation of broadening Rashba-type band in Au2Sb surface alloy
Here, we report a novel AuSb 2D superstructure on Au(111) that shows agreements and discrepancies to the expected electronic features of the ideal 2D surface alloys with $\sqrt{3}\times\sqrt{3}$ periodicity. Using spin- and angle-resolved photoemission spectroscopy, we find a significant spin splitting of the alloy ban...
2308.06183v2
2023-08-15
A primitive machine learning tool for the mechanical property prediction of multiple principal element alloys
Multi-principal element alloys (MPEAs) are produced by combining metallic elements in what is a diverse range of proportions. MPEAs reported to date have revealed promising performance due to their exceptional mechanical properties. Training a machine learning (ML) model on known performance data is a reasonable method...
2308.07649v1
2023-08-24
Two-dimensional germanium islands with Dirac signature on Ag2Ge surface alloy
Two-dimensional (2D) Dirac materials have attracted intense research efforts due to their promise for applications ranging from field-effect transistors and low-power electronics to fault-tolerant quantum computation. One key challenge is to fabricate 2D Dirac materials hosting Dirac electrons. Here, monolayer germanen...
2308.12878v1
2023-08-30
High-throughput assessment of the microstructural stability of segregation-engineered nanocrystalline Al-Ni-Y alloys
Segregation engineering has emerged as a promising pathway towards designing thermally stable nanocrystalline alloys with enhanced mechanical properties. However, the compositional and processing space for solute stabilized microstructures is vast, thus the application of high-throughput techniques to accelerate optima...
2308.16174v1
2023-09-09
$g$-factor engineering with InAsSb alloys toward zero band gap limit
Band gap is known as an effective parameter for tuning the Lande $g$-factor in semiconductors and can be manipulated in a wide range through the bowing effect in ternary alloys. In this work, using the recently developed virtual substrate technique, high-quality InAsSb alloys throughout the whole Sb composition range a...
2309.04779v1
2023-09-20
Superconductivity in the cobalt-doped V3Si A15 intermetallic compound
The A15 structure of superconductors is a prototypical type-II superconductor that has generated considerable interest since the early history of superconducting materials. This paper discusses the superconducting properties of previously unreported V3-xCoxSi alloys. It is found that the lattice parameter decreases wit...
2309.11055v1
2023-10-05
Serrated plastic flow in slowly-deforming complex concentrated alloys: universal signatures of dislocation avalanches
Under plastic flow, multi-element high/medium-entropy alloys (HEAs/MEAs) commonly exhibit complex intermittent and collective dislocation dynamics owing to inherent lattice distortion and atomic-level chemical complexities. Using atomistic simulations, we report on an avalanche study of slowly-driven model face-centere...
2310.03828v1
2023-10-16
Theoretical demonstration of the possibility of using binary alloys or solid solutions in ternary systems as geothermometers
The investigation of the processes of mineral deposit formation and their history is a fundamental task. Solving this task can increase mining efficiency and make a significant contribution to understanding the formation of the Earth's crust. The main approach to solving this task is determining the values of thermodyn...
2310.10099v1
2023-10-17
Periodic linear complexions: Co-segregation of solutes at a low-angle grain boundary in a magnesium alloy
Solute segregation at low angle grain boundaries (LAGB) in Mg alloys significantly affects GB energy and mobility, therefore recrystallization kinetics and corresponding texture modification. In a system featuring multiple substitutional elements at high local concentration levels, solute-solute interaction needs to be...
2310.11084v1
2023-10-18
A New Class of Materials Based on Nanoporous High Entropy Alloys with Outstanding Properties
Nanoporous metals with a random, bicontinuous structure of both pores and ligaments exhibit many unique mechanical properties, but their technical applications are often limited by their intrinsic brittleness under tensile strain triggered by fracture of the weakest ligaments. Here, we use molecular dynamics simulation...
2310.11937v1
2023-10-18
Deformation Mechanisms in High Entropy Alloys: A Minireview of Short-Range Order Effects
The complex atomic scale structure of high entropy alloys presents new opportunities to expand the deformation theories of mechanical metallurgy. In this regard, solute-defect interactions have emerged as critical piece in elucidating the operation of deformation mechanisms. While notable progress has been made in unde...
2310.12078v1
2023-10-19
Scaling and complexity of stress fluctuations associated with smooth and jerky flow in a FeCoNiTiAl high-entropy alloy
Recent observations of jerky flow in high-entropy alloys (HEA) revealed a high role of self-organization of dislocations in their plasticity. The present work reports first results of investigation of stress fluctuations during plastic deformation of a FeCoNiTiAl alloy, examined in a wide temperature range covering bot...
2310.12589v1
2023-10-24
Zr-Co-Al bulk metallic glass composites containing B2 ZrCo via rapid quenching and annealing
As a promising remedy for overcoming the limited ductility and work softening of bulk metallic glasses (BMGs), BMG composites incorporating a B2 crystalline phase have attracted considerable attention. Here, we explore the formation of Zr-Co-Al BMG composites by quenching alloys Zr$_{55}$Co$_{31}$Al$_{14}$, Zr$_{54.5}$...
2310.15521v1
2023-10-27
Grain Boundary Segregation Predicted by Quantum-Accurate Segregation Spectra but not by Classical Models
In alloys, solute segregation at grain boundaries is classically attributed to three driving forces: a high solution enthalpy, a high size mismatch, and a high difference in interfacial energy. These effects are generally cast into a single scalar segregation energy and used to predict grain boundary solute enrichment ...
2310.18447v2
2023-12-04
Negative Magnetization and Magnetic Ordering of Rare Earth and Transition Metal Sublattices in NdFe0.5Cr0.5O3
We investigate the effect of alloying at the 3d transition metal site of a rare-earth-transition metal oxide, by considering NdFe0.5Cr0.5O3 alloy with two equal and random distribution of 3d ions, Cr and Fe, interacting with an early 4f rare earth ion, Nd. Employing temperature- and field-dependent magnetization measur...
2312.01595v1
2023-12-21
Effective Phonon Dispersion of $β$- (Al$_x$Ga$_{1-x}$)$_2$O$_3$ alloy semiconductor
In this work, the Effective Phonon Dispersion of $\beta$- (Al$_x$Ga$_{1-x}$)$_2$O$_3$ alloy is investigated using the Phonon unfolding formalism. To capture the true randomness of the system, supercells are designed using the technique of special quasirandom structues. The phonon unfolding technique is then used to obt...
2312.14014v2
2023-12-22
Frustrated metastable-to-equilibrium grain boundary structural transition in NbMoTaW due to segregation and chemical complexity
Grain boundary structural transitions can lead to significant changes in the properties and performance of materials. In multi-principal element alloys, understanding these transitions becomes complex due to phenomena such as local chemical ordering and multi-component segregation. Using atomistic simulations, we explo...
2312.14344v2
2023-12-29
Accelerating Process Development for 3D Printing of New Metal Alloys
Addressing the uncertainty and variability in the quality of 3D printed metals can further the wide spread use of this technology. Process mapping for new alloys is crucial for determining optimal process parameters that consistently produce acceptable printing quality. Process mapping is typically performed by convent...
2401.00065v1
2024-01-05
Integrated ab initio modelling of atomic order and magnetic anisotropy for rare-earth-free magnet design: effects of alloying additions in $\mathrm{L}1_0$ FeNi
We describe an integrated modelling approach to accelerate the search for novel, single-phase, multicomponent materials with high magnetocrystalline anisotropy (MCA). For a given system we predict the nature of atomic ordering, its dependence on the magnetic state, and then proceed to describe the consequent MCA. Cruci...
2401.02809v1
2024-01-26
Accelerated intermetallic phase amorphization in a Mg-based high-entropy alloy powder
High-energy mechanical milling is employed to synthesize a stable high-entropy alloy powder from an otherwise immiscible Mg-Ti rich metallic mixture. Predictions from first principles and materials theory corroborate the results from microscopic characterizations that reveal a transition of the amorphous phase from a p...
2401.15197v1
2024-02-11
Langmuir-like model of dilute impurities in concentrated solid solutions
High-entropy alloys have drawn recent interest for their promising mechanical properties and irradiation resistance. Various properties, namely transport properties, are controlled by point defect concentration, which must be known before performing atomistic simulations to compute transport coefficients. In this work,...
2402.07324v1
2024-02-12
Chemical inhomogeneities in high-entropy alloys help mitigate the strength-ductility trade-off
Metallurgists have long been accustomed to a trade-off between yield strength and tensile ductility. Extending previously known strain-hardening mechanisms, the emerging multi-principal-element alloys (MPEAs) offer additional help in promoting the strength-ductility synergy, towards gigapascal yield strength simultaneo...
2402.07389v1
2024-02-14
Efficient Terahertz Generation from CoPt-based Terahertz Emitters via Orbital-to-Charge Conversion
Orbitronics devices operate by manipulating orbitally-polarized currents. Recent studies have shown that these orbital currents can be excited by femtosecond laser pulses in ferromagnet as Ni and converted into ultrafast charge current via orbital-to-charge conversion. However, the terahertz emission from orbitronic te...
2402.09228v1
2024-02-29
Magnetic properties of binary alloys Ni1-xMox and Ni1-yCuy close to critical concentrations
The search for the ferromagnetic quantum critical point (FM QCP) has always been a captivating research topic in the scientific community. In pursuit of this goal, we introduced nonmagnetic transition metals to alloy with elemental nickel, studying the magnetic properties of nickel binary alloys Ni1-xMox and Ni1-yCuy a...
2402.18902v1
2024-03-08
Superconductivity of the New Medium-Entropy Alloy V4Ti2W with a Body-Centered Cubic Structure
Medium- and high-entropy alloy (MEA and HEA) superconductors have attracted considerable interest since their discovery. This paper reports the superconducting properties of ternary tungsten-containing MEA V4Ti2W for the first time. V4Ti2W is a type II superconductor with a body-centered cubic (BCC) structure. Experime...
2403.05115v1
2024-03-10
Active Learning for Rapid Targeted Synthesis of Compositionally Complex Alloys
The next generation of advanced materials is tending toward increasingly complex compositions. Synthesizing precise composition is time-consuming and becomes exponentially demanding with increasing compositional complexity. An experienced human operator does significantly better than a beginner but still struggles to c...
2403.06329v1
2024-03-20
Spontaneous formation of Frenkel defects in high-entropy-alloys-type compound
High-entropy alloys (HEAs) are attracting attention due to their exceptional properties, such as enhanced mechanical toughness, superconducting robustness, and thermoelectric performance. Numerous HEAs have been developed for diverse applications, ranging from self-healing in fusion reactors to addressing environmental...
2403.13323v1
2024-03-24
AB5 type multicomponent TiVCoNiMn2 high-entropy alloy
Recent theoretical and practical research has focused on multi-component High Entropy Alloys (HEAs), which have superior mechanical and functional properties than standard alloys based on a single major element, thereby establishing a new field. A multi-component HEA contains five or more primary elements at concentrat...
2403.16241v1
2024-03-31
Low-loss liquid metal interconnects for modular superconducting quantum systems
Building modular architecture with superconducting quantum computing chips is one of the means to achieve qubit scalability, allowing the screening, selection, replacement, and integration of individual qubit modules into large quantum systems. However, the non-destructive replacement of modules within a compact archit...
2404.00770v1
1997-10-21
Cu-Au, Ag-Au, Cu-Ag and Ni-Au intermetallics: First-principles study of phase diagrams and structures
The classic metallurgical systems -- noble metal alloys -- that have formed the benchmark for various alloy theories, are revisited. First-principles fully relaxed general potential LAPW total energies of a few ordered structures are used as input to a mixed-space cluster expansion calculation to study the phase stabil...
9710225v1
2010-12-05
Influence of proteins from physiological solutions on the electrochemical behaviour of the Ti-6Al-4V alloy: reproducibility and time-frequency dependence. ---- Influence de la teneur en protéines de solutions physiologiques sur le comportement électrochimique du Ti-6Al-4V : reproductibilité et représentation temps-fréq...
The electrochemical behaviour of the biomedical and metallic alloys, especially in the orthopaedic implants fields, raises many questions. This study is dedicated for studying the Ti-6Al-4V alloy, by electrochemical impedance spectroscopy, EIS, in various physiological media,: Ringer solution, phosphate buffered soluti...
1012.0985v1
2011-09-13
Reentrant superconductivity in superconductor/ferromagnetic-alloy bilayers
We studied the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) like state establishing due to the proximity effect in superconducting Nb/Cu41Ni59 bilayers. Using a special wedge-type deposition technique, series of 20-35 samples could be fabricated by magnetron sputtering during one run. The layer thickness of only a few nanom...
1109.2757v1
2013-06-10
Lattice charge models and core level shifts in disordered alloys
Differences in core level binding energies between atoms belonging to the same chemical species can be related to differences in their intra- and extra-atomic charge distributions, and differences in how their core holes are screened. With this in mind, we consider the charge-excess functional model (CEFM) for net atom...
1306.2154v3
2014-02-19
Magnetism of PdNi alloys near the critical concentration for ferromagnetism
We report results of a muon spin rotation and relaxation ($\mu$SR) study of dilute Pd$_{1-x}$Ni$_x$ alloys, with emphasis on Ni concentrations $x =$ 0.0243 and 0.025. These are close to the critical value $x_\mathrm{cr}$ for the onset of ferromagnetic long-range order (LRO), which is a candidate for a quantum critical ...
1402.4532v1
2016-11-16
Growth of Ni and Ni-Cr Alloy Thin Films on MgO(001): Effect of Alloy Composition on Surface Morphology
The effects of substrate treatment, temperature and composition on the surface morphology of Ni-Cr thin films grown on MgO(001) are studied by scanning tunneling microscopy (STM) and atomic force microscopy (AFM). A combination of acid-etching and high temperature deposition (400C) will result in smooth films and terra...
1611.05495v1
2018-01-16
Electronic structure of the Mo$_{1-x}$Re$_x$ alloys studied through resonant photoemission spectroscopy
We have studied the electronic structure of Mo rich Mo$_{1-x}$Re$_x$ alloys (0$\leq$ x $\leq$0.4) using valence band photoemission spectroscopy in the photon energy range 23-70 eV and density of states calculations. Comparison of the photoemission spectra with the density of states calculations suggests that with respe...
1801.05087v1
2019-11-13
First principles analysis of electronic structure evolution and the indirect- to direct-gap transition in Ge$_{1-x}$Pb$_{x}$ group-IV alloys
We present a theoretical analysis of electronic structure evolution in the group-IV alloy Ge$_{1-x}$Pb$_{x}$ based on density functional theory. For ordered alloy supercells we demonstrate the emergence of a singlet conduction band (CB) edge state, suggesting the emergence of a direct band gap for Pb compositions as lo...
1911.05679v1
2018-10-25
Inhomogeneous magnon scattering during ultrafast demagnetization
Ni$_{0.8}$Fe$_{0.2}$ (Py) and Py alloyed with Cu exhibit intriguing ultrafast demagnetization behavior, where the Ni magnetic moment shows a delayed response relative to the Fe, an effect which is strongly enhanced by Cu alloying. We have studied a broad range of Cu concentrations to elucidate the effects of Cu alloyin...
1810.10994v1
2019-02-15
Magnetic states of Ni-Mn-Sn based shape memory alloy: a combined muon spin relaxation and neutron diffraction study
The fascinating multiple magnetic states observed in the Ni-Mn-Sn based metamagnetic shape memory alloy are addressed through a combined muon spin relaxation (muSR) and neutron powder diffraction studies. The material used in the present investigation is an off-stoichiometric alloy of nominal composition, Ni[2.04]Mn[1....
1902.05749v1
2022-02-25
TiFe$_{0.85}$Mn$_{0.05}$ alloy produced at industrial level for a hydrogen storage plant
In the use of hydrogen as large-scale energy vector, metal hydrides based on intermetallic compounds play a key role, thanks to mild temperatures and pressures required for the storage. It is increasingly necessary to develop hydrogen-based devices, and in this work, the intermetallic compound TiFe$_{0.85}$Mn$_{0.05}$ ...
2202.12753v1
2020-12-02
Strain-Rate-Dependent Deformation Behavior of Ti29Zr24Nb23Hf24 High Entropy Alloys at Elevated and Room Temperature
We investigate the strain-rate-dependent mechanical behavior and deformation mechanisms of a refractory high entropy alloy, Ti29Zr24Nb23Hf24 (at.%), with a single-phase body-centered cubic (BCC) structure. High-temperature compression tests were conducted at temperatures from 700 to 1100{\deg}C at strain rates ranging ...
2012.00954v1
2021-04-28
Structural transformation and magnetic properties of (Fe$_{0.7}$Co$_{0.3}$)$_2$B alloys doped with 5$d$ elements: A combined first-principles and experimental study
(Fe,Co)$_2$B-based compounds with specified 5$d$ substitutions are considered as promising materials for permanent magnets without rare-earth elements. We conducted a combined first-principles and experimental study focused on (Fe$_{0.7}$Co$_{0.3}$)$_2$B alloys doped with W and Re. First, we used full-potential local-o...
2104.13724v2
2021-05-17
The influence of beam focus during laser powder bed fusion of a high reflectivity aluminium alloy -- AlSi$_{10}$Mg
LPBF of Al alloys is associated with numerous challenges when compared to other commonly used alloys due to their higher reflectivity and thermal conductivity. In this work, processing diagrams, temperature prediction models, XCT, and metallography are used for establishing criteria in process parameter optimization of...
2105.07920v3
2021-06-11
Stacking fault energy induced softening in the nucleation limited plasticity regime: a molecular dynamics study on Cu-Al alloys
In general, with the addition of solutes, the yield strength of alloys is expected to increase and this phenomenon is known as solid solution strengthening. However, reports on the ``anomalous'' softening with alloying additions are not uncommon; for example, it is known that the heterogeneous nucleation of dislocation...
2106.06557v1
2022-04-29
Phase-Field Modeling of Coupled Brittle-Ductile Fracture in Aluminum Alloys
Fracture in aluminum alloys with precipitates involves at least two mechanisms, namely, ductile fracture of the aluminum-rich matrix and brittle fracture of the precipitates. In this work, a coupled crystal plasticity-phase field model for mixed ductile-brittle failure modes is formulated and used to investigate the ef...
2204.13994v1
2022-05-16
Thermal super-jogs control high-temperature strength in Nb-Mo-Ta-W alloys
Refractory multi-element alloys (RMEA) with body-centered cubic (bcc) structure have been the object of much research over the last decade due to their high potential as candidate materials for high-temperature applications. Most of these alloys display a remarkable strength at high temperatures, which cannot be explai...
2205.07413v1
2022-06-06
Mechanism of Local Lattice Distortion Effects on Vacancy Migration Barriers in FCC Alloys
Accurate prediction of vacancy migration energy barriers, $\Delta E_a$, in multi-component alloys is extremely challenging yet critical for the development of diffusional transformation kinetics needed to model alloy behavior in many technological applications. Here, results from $\Delta E_a$ and the energy driving for...
2206.02879v1
2022-09-23
Impact of random alloy fluctuations on the carrier distribution in multi-color (In,Ga)N/GaN quantum well systems
In this work, we study the impact that random alloy fluctuations have on the distribution of electrons and holes across the active region of a (In,Ga)N/GaN multi-quantum well based light emitting diode (LED). To do so, an atomistic tight-binding model is employed to account for alloy fluctuations on a microscopic level...
2209.11657v1
2022-10-26
Modeling of dendritic solidification and numerical analysis of the phase-field approach to model complex morphologies in alloys
Dendrites are one of the most widely observed patterns in nature and occur across a wide spectrum of physical phenomena. In solidification and growth patterns in metals and crystals, the multi-level branching structures of dendrites pose a modeling challenge, and a full resolution of these structures is computationally...
2210.14449v2
2022-12-06
Unidirectional Rashba Spin Splitting in Single Layer WS$_{2(1-x)}$Se$_{2x}$ alloy
Atomically thin two-dimensional (2D) layered semiconductors such as transition metal dichalcogenides (TMDs) have attracted considerable attention due to their tunable band gap, intriguing spin-valley physics, piezoelectric effects and potential device applications. Here we study the electronic properties of a single la...
2212.03248v1
2022-12-07
Orientation dependent pinning of (sub)grains by dispersoids during recovery and recrystallization in an Al-Mn alloy
The recrystallized grain size and texture in alloys can be controlled via the microchemistry state during thermomechanical processing. The influence of concurrent precipitation on recovery and recrystallization is here analyzed by directly correlating (sub)grains of P, CubeND or Cube orientation with second-phase parti...
2212.03527v1
2023-06-02
The phase stability of large-size nanoparticle alloy catalysts at ab initio quality using a nearsighted force-training approach
CoPt nanoparticle catalysts are integral to commercial fuel cells. Such systems are prohibitive to fully characterize with electronic structure calculations. Machine-learned potentials offer a scalable solution; however, such potentials are only reliable if representative training data can be employed, which typically ...
2306.01846v2
2023-06-07
Emergent Magnetic Phases and Piezomagnetic Effects in Mn$_x$Ni$_{1-x}$F$_2$ Thin Film Alloys
The effect of random competing single-ion anisotropies in antiferromagnets was studied using epitaxial Mn$_x$Ni$_{1-x}$F$_2$ antiferromagnetic thin film alloys grown via molecular beam epitaxy. The crystal structure of this material is tetragonal for all values of $x$, and the Mn sites have a magnetic easy axis single-...
2306.04809v2
2023-08-29
Sulfur Vacancy Related Optical Transitions in Graded Alloys of MoxW1-xS2 Monolayers
Engineering the electronic bandgap is of utmost importance in diverse domains ranging from information processing and communication technology to sensing and renewable energy applications. Transition metal dichalcogenides (TMDCs) provide an ideal platform for achieving this goal through techniques including alloying, d...
2308.14990v1
2024-04-11
Tunneling magnetoresistance in MgO tunnel junctions with Fe-based leads in empirically corrected density functional theory
The minority-spin Fe/MgO interface states are at the Fermi level in density functional theory (DFT), but experimental evidence and GW calculations place them slightly higher in energy. This small shift can strongly influence tunneling magnetoresistance (TMR) in junctions with a thin MgO barrier and its dependence on th...
2404.08103v1
1998-01-28
Electronic Structure, Local Moments and Transport in Fe_2VAl
Local spin density approximation calculations are used to elucidate electronic and magnetic properties of Heusler structure Fe_2VAl. The compound is found to be a low carrier density semimetal. The Fermi surface has small hole pockets derived from a triply degenerate Fe derived state at Gamma compensated by an V derive...
9801302v1
2002-05-29
Magnetic fluctuations and superconductivity in YbPd$_2$Sn
We report muon spin relaxation and inelastic neutron measurements on the Heusler system YbPd$_2$Sn. Localised anisotropic and quasi-elastic Yb magnetic fluctuations are observed below $T = 150$K. Both $\mu$SR and neutron data indicate a slowing-down of the spin-fluctuations, upon lowering the temperature, similar to th...
0205617v2
2003-10-16
Magnetotransport in Single Crystal Half-Heusler Compounds
We present the results of electrical resistivity and Hall effect measurements on single crystals of HfNiSn, TiPtSn, and TiNiSn. Semiconducting behavior is observed in each case, involving the transport of a small number of highly compensated carriers. Magnetization measurements suggest that impurities and site disorder...
0310369v2
2005-11-18
Half-metallic ferromagnetism with high magnetic moment and high Curie temperature in Co$_2$FeSi
Co$_2$FeSi crystallizes in the ordered L2$_1$ structure as proved by X-ray diffraction and M\"o\ss bauer spectroscopy. The magnetic moment of Co$_2$FeSi was measured to be about $6\mu_B$ at 5K. Magnetic circular dichroism spectra excited by soft X-rays (XMCD) were taken to determine the element specific magnetic moment...
0511463v1
2006-06-26
Epitaxial film growth and magnetic properties of Co_2FeSi
We have grown thin films of the Heusler compound Co_2FeSi by RF magnetron sputtering. On (100)-oriented MgO substrates we find fully epitaxial (100)-oriented and L2_1 ordered growth. On Al_2O_3 (11-20) substrates, the film growth is (110)-oriented, and several in-plane epitaxial domains are observed. The temperature de...
0606666v2
2006-09-25
Ion beam induced modification of exchange interaction and spin-orbit coupling in the Co$_2$FeSi Heusler compound
A Co$_2$FeSi (CFS) film with L2$_1$ structure was irradiated with different fluences of 30 keV Ga$^+$ ions. Structural modifications were subsequently studied using the longitudinal (LMOKE) and quadratic (QMOKE) magneto-optical Kerr effect. Both the coercivity and the LMOKE amplitude were found to show a similar behavi...
0609633v2
2006-09-27
Huge quadratic magneto-optical Kerr effect and magnetization reversal in the Co$_2$FeSi Heusler compound
Co$_2$FeSi(100) films with L2$_1$ structure deposited onto MgO(100) were studied exploiting both longitudinal (LMOKE) and quadratic (QMOKE) magneto-optical Kerr effect. The films exhibit a huge QMOKE signal with a maximum contribution of up to 30 mdeg, which is the largest QMOKE signal in reflection that has been measu...
0609688v2
2006-12-04
Structural, magnetic, and transport properties of Co$_2$FeSi Heusler films
We report the deposition of thin Co$_2$FeSi films by RF magnetron sputtering. Epitaxial (100)-oriented and L2$_1$ ordered growth is observed for films grown on MgO(100) substrates. (110)-oriented films on Al$_2$O$_3$(110) show several epitaxial domains in the film plane. Investigation of the magnetic properties reveals...
0612073v1
1998-10-07
Towards a classification of static electro-vacuum space-times containing an asymptotically flat spacelike hypersurface with compact interior
We show that static electro-vacuum black hole space-times containing an asymptotically flat spacelike hypersurface with compact interior and with both degenerate and non-degenerate components of the event horizon do not exist, under the supplementary hypothesis that all degenerate components of the event horizon have c...
9810022v3
2002-10-08
On "time-periodic" black-hole solutions to certain spherically symmetric Einstein-matter systems
This paper explores ``black hole'' solutions of various Einstein-wave matter systems admitting an isometry of their domain of outer communications taking every point to its future. In the first two parts, it is shown that such solutions, assuming in addition that they are spherically symmetric and the matter has a cert...
0210025v1
1996-05-13
Cosmological Analogues of the Bartnik--McKinnon Solutions
We present a numerical classification of the spherically symmetric, static solutions to the Einstein--Yang--Mills equations with cosmological constant $\Lambda$. We find three qualitatively different classes of configurations, where the solutions in each class are characterized by the value of $\Lambda$ and the number ...
9605089v1
1996-05-22
Stability Analysis of New Solutions of the EYM system with Cosmological Constant
We analyze the stability properties of the purely magnetic, static solutions to the Einstein--Yang--Mills equations with cosmological constant. It is shown that all three classes of solutions found in a recent study are unstable under spherical perturbations. Specifically, we argue that the configurations have $n$ unst...
9605166v1
2002-06-14
Statistics of Self-Crossings and Avoided Crossings of Periodic Orbits in the Hadamard-Gutzwiller Model
Employing symbolic dynamics for geodesic motion on the tesselated pseudosphere, the so-called Hadamard-Gutzwiller model, we construct extremely long periodic orbits without compromising accuracy. We establish criteria for such long orbits to behave ergodically and to yield reliable statistics for self-crossings and avo...
0206023v1
2003-09-05
Universal spectral form factor for chaotic dynamics
We consider the semiclassical limit of the spectral form factor $K(\tau)$ of fully chaotic dynamics. Starting from the Gutzwiller type double sum over classical periodic orbits we set out to recover the universal behavior predicted by random-matrix theory, both for dynamics with and without time reversal invariance. Fo...
0309022v1
2004-01-15
Semiclassical Foundation of Universality in Quantum Chaos
We sketch the semiclassical core of a proof of the so-called Bohigas-Giannoni-Schmit conjecture: A dynamical system with full classical chaos has a quantum energy spectrum with universal fluctuations on the scale of the mean level spacing. We show how in the semiclassical limit all system specific properties fade away,...
0401021v2
2005-03-23
Periodic-Orbit Theory of Universality in Quantum Chaos
We argue semiclassically, on the basis of Gutzwiller's periodic-orbit theory, that full classical chaos is paralleled by quantum energy spectra with universal spectral statistics, in agreement with random-matrix theory. For dynamics from all three Wigner-Dyson symmetry classes, we calculate the small-time spectral form...
0503052v1
2008-04-17
Electronic Structures of Fe$_{3-x}V$_x$Si Probed by Photoemission Spectroscopy
The electronic structures of the Heusler type compounds Fe$_{3-x}V$_x$Si in the concentration range between x = 0 and x = 1 have been probed by photoemission spectroscopy (PES). The observed shift of Si 2p core- level and the main valence band structres indicate a chemical potential shift to higher energy with increasi...
0804.2712v1
2008-09-18
Improvement of structural, electronic, and magnetic properties of Co$_2$MnSi thin films by He$^+$-irradiation
The influence of 30 keV He$^+$ ion irradiation on structural, electronic and magnetic properties of Co$_2$MnSi thin films with B2 order was investigated. It was found, that irradiation with light ions can improve the local chemical order. This provokes changes of the electronic structure and element-specific magnetizat...
0809.3192v1
2008-10-05
Brillouin light scattering study of Co$_{2}$Cr$_{0.6}$Fe$_{0.4}$Al and Co$_{2}$FeAl Heusler compounds
The thermal magnonic spectra of Co$_{2}$Cr$_{0.6}$Fe$_{0.4}$Al (CCFA) and Co$_2$FeAl were investigated using Brillouin light scattering spectroscopy (BLS). For CCFA, the exchange constant A (exchange stiffness D) is found to be 0.48 $\mu$erg/cm (203 meV A$^2$), while for Co$_2$FeAl the corresponding values of 1.55 $\mu...
0810.0838v2
2009-06-10
Periodic-orbit theory of universal level correlations in quantum chaos
Using Gutzwiller's semiclassical periodic-orbit theory we demonstrate universal behaviour of the two-point correlator of the density of levels for quantum systems whose classical limit is fully chaotic. We go beyond previous work in establishing the full correlator such that its Fourier transform, the spectral form fac...
0906.1960v2
2009-06-26
Near action-degenerate periodic-orbit bunches: A skeleton of chaos
Long periodic orbits of hyperbolic dynamics do not exist as independent individuals but rather come in closely packed bunches. Under weak resolution a bunch looks like a single orbit in configuration space, but close inspection reveals topological orbit-to-orbit differences. The construction principle of bunches involv...
0906.4930v1
2009-11-03
Seebeck coefficients of half-metallic ferromagnets
In this report the Co2 based Heusler compounds are discussed as potential materials for spin voltage generation. The compounds were synthesized by arcmelting and consequent annealing. Band structure calculations were performed and revealed the compounds to be half-metallic ferromagnets. Magnetometry was performed on th...
0911.0553v1
2010-10-27
Electronic structure of fully epitaxial Co2TiSn thin films
In this article we report on the properties of thin films of the full Heusler compound Co2TiSn prepared by DC magnetron co-sputtering. Fully epitaxial, stoichiometric films were obtained by deposition on MgO (001) substrates at substrate temperatures above 600{\deg}C. The films are well ordered in the L21 structure, an...
1010.5754v1
2010-11-11
Influence of tetragonal distortion on the magnetic and electronic properties of the Heusler compound Co2TiSn from first principles
Using the full potential linearized augmented plane wave plus local orbitals method we determine ab-initio the lattice parameters of tetragonally distorted Co2TiSn in the L21 structure. The tetragonal lattice parameter c is determined as a function of the lattice parameter a by energy minimization. The change in total ...
1011.2657v1
2010-12-14
Scaling behavior of the spin pumping effect in ferromagnet/platinum bilayers
We systematically measured the DC voltage V_ISH induced by spin pumping together with the inverse spin Hall effect in ferromagnet/platinum bilayer films. In all our samples, comprising ferromagnetic 3d transition metals, Heusler compounds, ferrite spinel oxides, and magnetic semiconductors, V_ISH invariably has the sam...
1012.3017v2
2010-12-15
Exchange interactions and Curie temperatures in Mn2CoZ compounds
The generalized Heusler compounds Mn2CoZ (Z = Al, Ga, In, Si, Ge, Sn, Sb) with the Hg2CuTi structure are of large interest due to their half-metallic ferrimagnetism. The complex magnetic interactions between the constituents are studied by first principles calculations of the Heisenberg exchange coupling parameters, an...
1012.3261v1
2011-01-06
Metallic surface electronic state in half-Heusler compounds RPtBi (R = Lu, Dy, Gd)
Rare-earth platinum bismuth (RPtBi) has been recently proposed to be a potential topological insulator. In this paper we present measurements of the metallic surface electronic structure in three members of this family, using angle resolved photoemission spectroscopy (ARPES). Our data shows clear spin-orbit splitting o...
1101.1261v1
2011-01-31
Ferrimagnetism and disorder in epitaxial Mn(2-x)Co(x)VAl thin films
The quaternary full Heusler compound Mn(2-x)Co(x)VAl with x = 1 is predicted to be a half-metallic antiferromagnet. Thin films of the quaternary compounds with x = 0...2 were prepared by DC and RF magnetron co-sputtering on heated MgO (001) substrates. The magnetic structure was examined by x-ray magnetic circular dich...
1101.5994v1
2011-06-19
Magnetic and transport properties of rare-earth-based half-Heusler phases RPdBi: prospective systems for topological quantum phenomena
RPdBi (R = Er, Ho, Gd, Dy, Y, Nd) compounds were studied by means of x-ray diffraction, magnetic susceptibility, electrical resistivity, magnetoresistivity, thermoelectric power and Hall effect measurements, performed in the temperature range 1.5-300 K and in magnetic fields up to 12 T. These ternaries, except diamagne...
1106.3763v1
2011-09-05
Superconductivity in the topological semimetal YPtBi
The noncentrosymmetric Half Heusler compound YPtBi exhibits superconductivity below a critical temperature T_c = 0.77 K with a zero-temperature upper critical field H_c2(0) = 1.5 T. Magnetoresistance and Hall measurements support theoretical predictions that this material is a topologically nontrivial semimetal having ...
1109.0979v2
2011-09-16
Magnetic order in GdBiPt studied by x-ray resonant magnetic scattering
Rare earth (R) half-Heusler compounds, RBiPt, exhibit a wide spectrum of novel ground states. Recently, GdBiPt has been proposed as a potential antiferromagnetic topological insulator (AFTI). We have employed x-ray resonant magnetic scattering to elucidate the microscopic details of the magnetic structure in GdBiPt bel...
1109.3521v1
2011-11-04
Electronic structure and symmetry of valence states of epitaxial NiTiSn and NiZr$_{0.5}$Hf$_{0.5}$Sn thin films by hard x-ray photoelectron spectroscopy
The electronic band structure of thin films and superlattices made of Heusler compounds with NiTiSn and NiZr$_{0.5}$Hf$_{0.5}$Sn composition was studied by means of polarization dependent hard x-ray photoelectron spectroscopy. The linear dichroism allowed to distinguish the symmetry of the valence states of the differe...
1111.1031v1
2012-07-11
Optical floating zone growth of high-quality Cu2MnAl single crystals
We report the growth of large single-crystals of Cu2MnAl, a ferromagnetic Heusler compound suitable for polarizing neutron monochromators, by means of optical floating zone under ultra-high vacuum compatible conditions. Unlike Bridgman or Czochralsky grown Cu2MnAl, our floating zone grown single-crystals show highly re...
1207.2803v1
2012-10-10
Negative spin polarization of Mn2VGa probed by tunnel magnetoresistance
The ferrimagnetic Heusler compound Mn2VGa is predicted to have a pseudogap in the majority spin channel, which should lead to a negative tunnel magnetoresistance. We synthesized epitaxial Mn2VGa thin films on MgO(001) substrates by dc and rf magnetron co-sputtering, resulting in nearly stoichiometric films. XRD analysi...
1210.2966v1
2012-11-12
Magnetic and transport properties of tetragonal- or cubic-Heusler-type Co-substituted Mn-Ga epitaxial thin films
The composition dependence of the structural, magnetic, and transport properties of epitaxially grown Mn-Co-Ga films were investigated. The crystal structure was observed to change from tetragonal to cubic as the Co content was increased. In terms of the dependence of saturation magnetization on the Co content, relativ...
1211.2524v1
2013-02-21
Large zero-field cooled exchange-bias in bulk Mn2PtGa
We report a large exchange-bias (EB) effect after zero-field cooling the new tetragonal Heusler compound Mn2PtGa from the paramagnetic state. The first-principle calculation and the magnetic measurements reveal that Mn2PtGa orders ferrimagnetically with some ferromagnetic (FM) inclusions. We show that ferrimagnetic (FI...
1302.5229v1
2013-03-14
Thermal Stability and Electrical Control of Magnetization of Heusler/Oxide Interface and Non-collinear Spin Transport of Its Junction
Towards next-generation spintronics devices, such as computer memories and logic chips, it is necessary to satisfy high thermal stability, low-power consumption and high spin-polarization simultaneously. Here, from first-principles, we investigate thermal stability (both structure and magnetization) and the electric fi...
1303.3473v2
2013-04-22
Giant enhancement of spin pumping efficiency using Fe3Si ferromagnet
Spincurrentronics, which involves the generation, propagation and control of spin currents, has attracted a great deal of attention because of the possibility of realizing dissipation-free information propagation. Whereas electrical generation of spin currents originally made the field of spincurrentronics possible, an...
1304.5890v1
2013-09-25
Ab-initio calculation of the effective on-site Coulomb interaction parameters for half-metallic magnets
Correlation effects play an important role in the electronic structure of half-metallic (HM) magnets. In particular, they give rise to non-quasiparticle states above (or below) the Fermi energy at finite temperatures that reduce the spin polarization and, as a consequence, the efficiency of spintronics devices. Employi...
1309.6657v1
2013-11-26
Large enhancement in the generation efficiency of pure spin currents in Ge using Heusler-compound Co_2FeSi electrodes
We show nonlocal spin transport in n-Ge based lateral spin-valve devices with highly ordered Co_2FeSi/n^+-Ge Schottky tunnel contacts. Clear spin-valve signals and Hanle-effect curves are demonstrated at low temperatures, indicating generation, manipulation, and detection of pure spin currents in n-Ge. The obtained spi...
1311.6601v1
2014-01-25
Investigation of thermoelectric properties of half-metallic Co2 MnGe by using first principles calculations
By combining the electronic structures obtained from first principles calculations with Boltzmann transport theory we have investigated the electronic, magnetic and transport properties of Co$_{2}$MnGe Heusler compound. The density of states plots, dispersion curves and total energy of paramagnetic and ferromagnetic (F...
1401.6511v2
2014-10-02
Investigation of the temperature-dependence of ferromagnetic resonance and spin waves in Co2FeAl0.5Si0.5
Co2FeAl0.5Si0.5 (CFAS) is a Heusler compound that is of interest for spintronics applications, due to its high spin polarization and relatively low Gilbert damping constant. In this study, the behavior of ferromagnetic resonance as a function of temperature was investigated in CFAS, yielding a decreasing trend of dampi...
1410.0439v1
2014-12-07
Prediction and accelerated laboratory discovery of previously unknown 18-electron ABX compounds
Chemists and material scientists have often focused on the properties of previously reported compounds, leaving out numerous unreported but chemically plausible compounds that could have interesting properties. For example, the 18-valence electron ABX family of compounds includes the half-Heusler subgroup, and features...
1412.2398v1