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2002-03-07
Resonant x-ray emission spectra of Mn based Heusler alloys
The Mn L_2,L_3 x-ray spectra of the Cu_2MnAl and Co_2MnZ (Z=Al,Ga, Sn, Sb) Heusler alloys have been investigated by the Resonant X-ray Emission Spectroscopy (RXES) using linearly polarized monochromatic synchrotron radiation for. The interplay between the half-metallic character of the Mn 3d electronic structure in con...
0203169v1
2002-09-25
Magnetic properties of Ni2.18Mn0.82Ga Heusler alloys with a coupled magnetostructural transition
Polycrystalline Ni2.18Mn0.82Ga Heusler alloys with a coupled magnetostructural transition are studied by differential scanning calorimetry, magnetic and resistivity measurements. Coupling of the magnetic and structural subsystems results in unusual magnetic features of the alloy. These uncommon magnetic properties of N...
0209574v1
2004-06-24
Electronic Structure and Magnetic Exchange Coupling in Ferromagnetic Full Heusler Alloys
Density-functional studies of the electronic structures and exchange interaction parameters have been performed for a series of ferromagnetic full Heusler alloys of general formula Co$_2$MnZ (Z = Ga, Si, Ge, Sn), Rh$_2$MnZ (Z = Ge, Sn, Pb), Ni$_2$MnSn, Cu$_2$MnSn and Pd$_2$MnSn, and the connection between the electroni...
0406588v1
2004-08-03
Half-metallicity and Slater-Pauling behavior in the ferromagnetic Heusler alloys
Introductory chapter for the book "Halfmetallic Alloys - Fundamentals and Applications" to be published in the series Springer Lecture Notes on Physics, P. H. Dederichs and I. Galanakis (eds). It contains a review of the theoretical work on the half-metallic Heusler alloys.
0408068v1
2006-03-23
Inverted spin polarization of Heusler alloys for new spintronic devices
A new magnetic logic overcomes the major limitations of field programmable gate arrays while having a 50% smaller unit cell than conventional designs utilizing magnetic tunnel junctions with one Heusler alloy electrode. These show positive and negative TMR values at different bias voltages at room temperature which gen...
0603616v1
2006-03-30
Effect of doping and disorder on the half-metallicity of full Heusler alloy
Heusler alloys containing Co and Mn are amongst the most heavily studied half-metallic ferromagnets for future applications in spintronics. Using state-of-the-art electronic structure calculations, we investigate the effect of doping and disorder on their electronic and magnetic properties. Small degrees of doping by s...
0603811v1
2006-09-20
Towards a full Heusler alloy showing room temperature half-metallicity at the surface
In this article we investigate the surface spin polarization in a 100 nm Co2Cr0.6Fe0.4Al (CCFA) film grown ex situ epitaxially on MgO(100) with a 10 nm Fe buffer layer by means of spin resolved photoemission. We show that a careful in situ preparation of the sample surface leads to values for the room temperature spin ...
0609504v1
1995-03-28
THE UNIQUENESS THEOREM FOR ROTATING BLACK HOLE SOLUTIONS OF SELF-GRAVITATING HARMONIC MAPPINGS
We consider rotating black hole configurations of self-gravitating maps from spacetime into arbitrary Riemannian manifolds. We first establish the integrability conditions for the Killing fields generating the stationary and the axisymmetric isometry (circularity theorem). Restricting ourselves to mappings with harmoni...
9503053v1
1995-06-15
Pulsation of Spherically Symmetric Systems in General Relativity
The pulsation equations for spherically symmetric black hole and soliton solutions are brought into a standard form. The formulae apply to a large class of field theoretical matter models and can easily be worked out for specific examples. The close relation to the energy principle in terms of the second variation of t...
9506027v1
1996-10-11
No-Hair Theorems and Black Holes with Hair
The critical steps leading to the uniqueness theorem for the Kerr-Newman metric are reexamined in the light of the new black hole solutions with Yang-Mills and scalar hair. Various methods -- including scaling techniques, arguments based on energy conditions, conformal transformations and divergence identities -- are r...
9610019v1
1997-03-06
Mass formulae for a class of nonrotating black holes
In the presence of a Killing symmetry, various self-gravitating field theories with massless scalars (moduli) and vector fields reduce to sigma-models, effectively coupled to 3-dimensional gravity. We argue that this particular structure of the Einstein-matter equations gives rise to quadratic relations between the asy...
9703015v1
1998-05-15
On rotational excitations and axial deformations of BPS monopoles and Julia-Zee dyons
It is shown that Julia-Zee dyons do not admit slowly rotating excitations. This is achieved by investigating the complete set of stationary excitations which can give rise to non-vanishing angular momentum. The relevant zero modes are parametrized in a gauge invariant way and analyzed by means of a harmonic decompositi...
9805061v1
2001-05-22
Semiclassical evidence for the BGS-conjecture
Recently, M. Sieber and K. Richter achieved a breakthrough towards a proof of the BGS-conjecture by calculating semiclassically a first correction to the diagonal approximation of the orthogonal form factor for geodesic flow on a Riemann surface of constant negative curvature. In this note, we try to generalize the arg...
0105052v3
2001-06-22
Near action degeneracy of periodic orbits in systems with non-conventional time reversal
Recently, Sieber and Richter calculated semiclassically a first off-diagonal contribution to the orthogonal form factor for a billiard on a surface of constant negative curvature by considering orbit pairs having almost the same action. For a generalization of this derivation to systems invariant under non-conventional...
0106035v1
2007-11-05
Magnetization easy-axis in martensitic Heusler alloys estimated by strain measurements under magnetic-field
We study the temperature dependence of strain under constant magnetic-fields in Ni-Mn based ferromagnetic Heusler alloys in the form Ni-Mn-$X$ ($X$: Ga, In, Sn, Sb) which undergo a martensitic transformation. We discuss the influence of the applied magnetic-field on the nucleation of ferromagnetic martensite and extrac...
0711.0639v1
2011-02-18
Perpendicular magnetic anisotropy of full-Heusler films in Pt/Co2FeAl/MgO trilayers
We report on perpendicular magnetic anisotropy (PMA) in a Pt/Co2FeAl/MgO sandwiched structure with a thick Co2FeAl layer of 2-2.5 nm. The PMA is thermally stable that the anisotropy energy density Ku is 1.3{\times}106 erg/cm3 for the structure with 2 nm Co2FeAl after annealing at 350 oC. The thicknesses of Co2FeAl and ...
1102.3802v1
2012-06-06
Probing the superconducting state of the Heusler supercoductor: ZrNi$_2$Ga
Using both muon spin rotation and muon spin relaxation, the superconducting ground state of the Heusler superconductor {ZrNi$_2$Ga} has been studied. The temperature dependence of the magnetic penetration depth of {ZrNi$_2$Ga} is consistent with a single isotropic gap s-wave BCS superconductor. The gap energy is \Delta...
1206.1182v1
2015-01-03
First-principles study of four quaternary Heusler alloys ZrMnVZ and ZrCoFeZ (Z=Si, Ge)
We investigate the electronic structure and magnetic properties of four quaternary Heusler alloys ZrMnVZ and ZrCoFeZ (Z=Si, Ge) by using first-principle calculations. It is shown that ZrMnVSi, ZrMnVGe and ZrCoFeSi are half-metallic ferromagnets with considerable half-metallic gaps of 0.14, 0.18 and 0.22 eV, respectivel...
1501.00542v1
2018-03-30
Boosting Material Modeling Using Game Tree Search
We demonstrate a heuristic optimization algorithm based on the game tree search for multi-component materials design. The algorithm searches for the largest spin polarization of seven-component Heusler alloys. The algorithm can find the peaks quickly and is more robust against local optima than Bayesian optimization ap...
1803.11338v2
2018-06-18
Large anomalous Nernst effect across the magneto-structural transition in bulk Ni-Co-Mn-Sn full Heusler alloy
We report on the observation of temperature and field dependent anomalous Nernst effect (ANE) in Ni-rich bulk Ni-Co-Mn-Sn full Heusler alloy. A large change in the transverse Nernst coefficient (N) is obtained across the first order magnetostructural transition from a tetragonal martensite to a cubic austenite phase. T...
1806.06675v1
2018-11-09
Anomaly in anomalous Nernst effect at low temperature for C1b-type NiMnSb half-Heusler alloy thin film
The anomaly in the anomalous Nernst effect (ANE) was observed for a C1b-type NiMnSb half-Heusler alloy thin film deposited on a MgO (001) substrate. The Nernst angle ({\theta}ANE) showed maximum peak with decreasing temperature and reached 0.15 at 80 K, which is considered to be brought by the cross-over from half-meta...
1811.03791v1
2020-01-17
Fermi Level Controlled Ultrafast Demagnetization Mechanism in Half-Metallic Heusler Alloy
The electronic band structure-controlled ultrafast demagnetization mechanism in Co2FexMn1-xSi Heusler alloy is underpinned by systematic variation of composition. We find the spin-flip scattering rate controlled by spin density of states at Fermi level is responsible for non-monotonic variation of ultrafast demagnetiza...
2001.06217v1
2022-01-14
Antisite disorder and phase segregation in Mn$_{2}$NiSn
A systematic study of crystal structure, local structure, magnetic and transport properties in quenched and temper annealed Ni$_{2-x}$Mn$_{1+x}$Sn alloys indicate the formation of Mn$_3$Sn type structural defects caused by an antisite disorder between Mn and Sn occupying the Y and Z sublattices of X$_2$YZ Heusler struc...
2201.05283v1
2022-12-19
Chiral surface superconductivity in half-Heusler semimetals
We propose the metallic and weakly dispersive surface states of half-Heusler semimetals as a possible domain for the onset of unconventional surface superconductivity ahead of the bulk transition. Using density functional theory (DFT) calculations and the random phase approximation (RPA), we analyse the surface band st...
2212.09786v1
2023-02-13
Half-metallicity in $Ni_2XMn$ Heusler alloys ($X=Fe,Co,Cr$): ab-initio calculations
Lattice parameter, bulk modulus, formation energy and magnetism equilibrium structure in all-d transition metals $Ni_2XMn$ (X=Co,Cr,Fe) for Full and Inverse Heusler structure are studied by first-principles calculations. Tetragonal distortion is calculated for the equilibrium volume of each alloy and possible new equil...
2302.06450v1
2007-12-02
Role of the conduction electrons in mediating exchange interactions in Heusler alloys
Because of large spatial separation of the Mn atoms in Heusler alloys the Mn 3d states belonging to different atoms do not overlap considerably. Therefore an indirect exchange interaction between Mn atoms should play a crucial role in the ferromagnetism of the systems. To study the nature of the ferromagnetism of vario...
0712.0158v1
2012-12-01
On the half-metallicity of Co2FeSi Heusler alloy: an experimental and ab initio study
Co2FeSi, a Heusler alloy with the highest magnetic moment per unit cell and the highest Curie temperature, has largely been described theoretically as a half-metal. This conclusion, however, disagrees with Point Contact Andreev Reflection (PCAR) spectroscopy measurements, which give much lower values of spin polarizati...
1212.0168v1
2013-01-27
Spintronic properties and stability of the half-Heusler alloys LiMnZ (Z=N, P, Si)
Li-based half-Heusler alloys have attracted much attention due to their potential applications in optoelectronics and because they carry the possibility of exhibiting large magnetic moments for spintronic applications. Due to their similarities to metastable zinc blende half-metals, the half-Heusler alloys $\beta$-LiMn...
1301.6367v3
2016-04-26
First principles studies of the Gilbert damping and exchange interactions for half-metallic Heuslers alloys
Heusler alloys have been intensively studied due to the wide variety of properties that they exhibit. One of these properties is of particular interest for technological applications, i.e. the fact that some Heusler alloys are half-metallic. In the following, a systematic study of the magnetic properties of three diffe...
1604.07552v1
2018-01-09
Epitaxial Heusler Superlattice Co2MnAl/Fe2MnAl with Perpendicular Magnetic Anisotropy and Termination-Dependent Half-Metallicity
Single-crystal Heusler atomic-scale superlattices that have been predicted to exhibit perpendicular magnetic anisotropy and half-metallicity have been successfully grown by molecular beam epitaxy. Superlattices consisting of full-Heusler Co$_2$MnAl and Fe$_2$MnAl with one to three unit cell periodicity were grown on Ga...
1801.02787v1
2019-02-20
Spin-charge conversion in NiMnSb Heusler alloy films
Half-metallic Heusler alloys are attracting considerable attention because of their unique half-metallic band structures which exhibit high spin polarization and yield huge magnetoresistance ratios. Besides serving as ferromagnetic electrodes, Heusler alloys also have the potential to host spin-charge conversion which ...
1902.07406v1
2020-02-11
A simple model for vacancy order and disorder in defective half-Heusler systems
Defective half-Heusler systems X(1-x)YZ with large amounts of intrinsic vacancies, such as Nb(1-x)CoSb, Ti(1-x)NiSb and V(1-x)CoSb, are a group of promising thermoelectric materials. Even with high vacancy concentrations they maintain the average half-Heusler crystal structure. These systems show high electrical conduc...
2002.04281v2
2021-02-22
Structural, magnetic, and magnetocaloric properties of Fe2CoAl Heusler nanoalloy
Spherical nanoparticles (NPs) of size 14 nm, made of intermetallic Fe2CoAl (FCA) Heusler alloy, are synthesized via the co-precipitation and thermal deoxidization method. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns confirm that the present nanoalloy is crystallized in A2-disordered cu...
2102.11195v2
2022-12-02
FeRhCrSi: A new spin semimetal with room temperature spin-valve behavior
Spin semimetals are a recently discovered new class of spintronic materials, which exhibit a band gap in one spin channel while a semimetallic feature in the other and thus allows for tunable spin transport. Here, we present experimental verification of spin semimetallic behavior in FeRhCrSi, a quaternary Heusler alloy...
2212.00924v2
2023-03-17
Intrinsic and extrinsic anomalous transport properties of Heusler ferromagnets Fe$_2$CoAl and Fe$_2$NiAl from first principles
Recently, Heusler ferromagnets have been found to exhibit unconventional anomalous electric, thermal, and thermoelectric transport properties. In this study, we employed first-principles density functional theory calculations to systematically investigate both intrinsic and extrinsic contributions to the anomalous Hall...
2303.09812v2
2023-10-24
Tuning the topological character of half-Heusler systems: A comparative study on Y$T$Bi ($T$ = Pd, Pt)
Half-Heusler systems host a plethora of different ground states, especially with non-trivial topology. However, there is still a lack of spectroscopic insight into the corresponding band inversion in this family. In this work, we locally explore the half-Heuslers Y$T$Bi ($T =$ Pt and Pd) by means of scanning tunneling ...
2310.15708v1
2006-11-17
Electronic structure of half-metallic magnets
We have analyzed the electronic structure of half-metallic magnets based on first principles electronic structure calculations of a series of semi-Heusler alloys. The characteristic feature of the electronic structure of semi-Heusler systems is a d-d gap in the density of states lying at/close to the Fermi level depend...
0611476v1
2008-11-10
Tuning the magnetic properties of half-metallic semi-Heusler alloys by sp-electron substitution: The case of AuMnSn$_{1-x}$Sb$_x$ quaternary alloys
We study the electronic and magnetic properties of the quaternary AuMnSn$_{1-x}$Sb$_{x}$ Heusler alloys using first principles calculations. We determine their magnetic phase diagram and we show that they present a phase transition from a ferromagnetic to an antiferromagnetic state with increasing Sb concentration. For...
0811.1408v1
2009-02-09
Analysis of L21-ordering in full-Heusler Co2FeSi alloy thin films formed by rapid thermal annealing
The authors developed a new analysis approach for evaluation of atomic ordering in full-Heusler alloys, which is extension of the commonly used Webster model. Our model can give accurate physical formalism for the degree of atomic ordering in the L21 structure, including correction with respect to the fully disordered ...
0902.1438v1
2009-06-16
Epitaxial Growth of a Full-Heusler Alloy Co$_{2}$FeSi on Silicon by Low-Temperature Molecular Beam Epitaxy
For electrical spin injection and detection of spin-polarized electrons in silicon, we explore highly epitaxial growth of ferromagnetic full-Heusler-alloy Co2FeSi thin films on silicon substrates using low-temperature molecular beam epitaxy (LTMBE). Although in-situ reflection high energy electron diffraction images cl...
0906.2840v1
2009-10-26
Direct determination of the surface termination in full Heusler alloys by means of low energy electron diffraction
The performance of Heusler based magnetoresistive multilayer devices depends crucially on the spin polarization and thus on the structural details of the involved surfaces. Using low energy electron diffraction (LEED), one can non-destructively distinguish between important surface terminations of Co2XY full-Heusler al...
0910.4909v2
2010-06-01
Observation of enhanced exchange bias behavior in NiCoMnSb Heusler alloys
We report the observation of large exchange bias in Ni50-xCoxMn38Sb12 Heusler alloys with x=0, 2, 3, 4, 5, which is attributed to the coexistence of ferromagnetic and antiferromagnetic phases in the martensitic phase. The phase coexistence is possibly due to the supercooling of the high temperature ferromagnetic phase ...
1006.0071v1
2012-06-11
Crossover from antiferromagnetic to ferromagnetic ordering in semi-Heusler alloys Cu1-xNixMnSb with increasing Ni concentration
The magnetic properties and transition from an antiferromagnetic (AFM) to a ferromagnetic (FM) state in semi Heusler alloys Cu1-xNixMnSb, with x < 0.3 have been investigated in details by dc magnetization, neutron diffraction, and neutron depolarization. We observe that for x < 0.05, the system Cu1-xNixMnSb is mainly i...
1206.2243v1
2012-11-02
Interface characterization of Co2MnGe/Rh2CuSn Heusler multilayers
All-Heusler multilayer structures have been investigated by means of high kinetic x-ray photoelectron spectroscopy and x-ray magnetic circular dichroism, aiming to address the amount of disorder and interface diffusion induced by annealing of the multilayer structure. The studied multilayers consist of ferromagnetic Co...
1211.0489v2
2013-04-09
Half-metallicity and anisotropy magnetoresistance properties of Heusler alloys Fe2Co1-xCrxSi
In this paper, we investigate the half-metallicity of Heusler alloys Fe2Co1-xCrxSi by first principles calculations and anisotropy magnetoresistance measurements. It is found that, with the increase of Cr content x, the Fermi level of Fe2Co1-xCrxSi moves from the top of valence band to the bottom of conduction band, an...
1304.2602v1
2013-07-11
Large Linear Magnetoresistance and Shubnikov-de Hass Oscillations in Single Crystals of YPdBi Heusler Topological Insulators
We report the observation of a large linear magnetoresistance (MR) and Shubnikov-de Hass (SdH) quantum oscillations in single crystals of YPdBi Heusler topological insulators. Owning to the successfully obtained the high-quality YPdBi single crystals, large non-saturating linear MR of as high as 350% at 5K and over 120...
1307.3022v1
2013-11-22
Full-Heusler Co2FeSi alloy thin films with perpendicular magnetic anisotropy induced by MgO-interface
The authors demonstrated that L21-ordered full-Heusler Co2FeSi (CFS) alloy film with thickness of 100 nm were formed by facing targets sputtering (FTS) method at a substrate temperature TS = 300 deg C. Degrees of L21- and B2- order for the film were 0.37, and 0.96, respectively. Furthermore, full-Heusler CFS alloy thin...
1311.5670v2
2014-02-18
Interplay of growth mode and thermally induced spin accumulation in epitaxial Al/Co$_2$TiSi/Al and Al/Co$_2$TiGe/Al contacts
The feasibility of thermally driven spin injectors built from half-metallic Heusler alloys inserted between aluminum leads was investigated by means of {\em ab initio} calculations of the thermodynamic equilibrium and electronic transport. We have focused on two main issues and found that: (i) the interface between Al ...
1402.4396v2
2014-10-07
Anti-site disorder and improved functionality of Mn$_{2}$Ni{\it X} ({\it X}= Al, Ga, In, Sn) inverse Heusler alloys
Recent first-principles calculations have predicted Mn$_{2}$Ni{\it X} ({\it X}=Al, Ga, In, Sn) alloys to be magnetic shape memory alloys. Moreover, experiments on Mn$_{2}$NiGa and Mn$_{2}$NiSn suggest that the alloys deviate from the perfect inverse Heusler arrangement and that there is chemical disorder at the sublatt...
1410.1690v1
2014-11-27
$Ab$ $intito$ study on some new spin-gapless semiconductors: The Zr-based quanternary Heusler alloys
Employing $ab$ $intito$ electronic structure calculations, we have investigated electronic and magnetic properties of the Zr-based quanternary Heusler alloys: ZrCoVIn, ZrFeVGe, ZrCoFeP, ZrCoCrBe and ZrFeCrZ (Z=In and Ga). Our $ab$ $intito$ calculation results show that all the alloys are (or nearly) spin-gapless semico...
1411.7570v2
2015-06-22
Two successive magneto-structural transformations and their relation to enhanced magnetocaloric effect for Ni55.3Mn19.7Ga25 Heusler alloy
In the present work, two successive magneto-structural transformations (MSTs) consisting of martensitic and intermartensitic transitions have been reported in polycrystalline Ni55.8Mn18.1Ga26.1 Heusler alloy. Benefiting from the additional latent heat contributed from intermediate phase, this alloy exhibits a large tra...
1506.06517v2
2015-08-07
Multifunctional Heusler alloy: experimental evidences of enhanced magnetocaloric properties at room temperature and half-metallicity
Heusler alloys are widely studied due to their interesting structural and magnetic properties, like magnetic memory shape ability, coupled magneto-structural phase transitions and half-metallicity; ruled, for many cases, by the valence electrons number ($N_v$). The present work focuses on the magnetocaloric potentials ...
1508.01828v1
2016-04-19
Half Heusler Alloys for Efficient Thermoelectric Power Conversion
Half-Heusler (HH) phases (space group F43m, Clb) are increasingly gaining attention as promising thermoelectric materials in view of their thermal stability, scalability, and environmental benignity as well as efficient power output. Until recently, the verifiable dimensionless figure of merit (ZT) of HH phases has rem...
1604.05397v2
2019-11-22
Superconducting spin-valve effect in heterostructures with ferromagnetic Heusler alloy layers
We report a comparative analysis and theoretical description of the superconducting properties of two spin-valve-valve structures containing the Heusler alloy Co$_2$Cr$_{1-x}$Fe$_x$Al$_{y}$ as one of two ferromagnetic (F1 or F2) layers of the F1/F2/S structure, where S stands for the superconducting Pb layer. In our ex...
1911.09984v1
2017-04-04
Model Hamiltonian and Time Reversal Breaking Topological Phases of Anti-ferromagnetic Half-Heusler Materials
In this work, we construct a generalized Kane model with a new coupling term between itinerant electron spins and local magnetic moments of anti-ferromagnetic ordering in order to describe the low energy effective physics in a large family of anti-ferromagnetic half-Heusler materials. Topological properties of this gen...
1704.01138v1
2017-05-17
High Thermoelectric Figure of Merit by Resonant Dopant in Half-Heusler Alloys
Half-Heusler alloys have been one of the benchmark high temperature thermoelectric materials owing to their thermal stability and promising figure of merit ZT. Simonson et al. early showed that small amounts of vanadium doped in Hf0.75Zr0.25NiSn enhanced the Seebeck coefficient and correlated the change with the increa...
1705.06100v1
2018-07-17
Ferromagnetically correlated clusters in semi-metallic Ru2NbAl Heusler alloy
In this work, we report the structural, magnetic and electrical and thermal transport properties of the Heusler-type alloy Ru2NbAl. From the detailed analysis of magnetization data, we infer the presence of superparamagnetically interacting clusters with a Pauli paramagnetic background, while short-range ferromagnetic ...
1807.06608v1
2019-01-27
Computational search for ultrasmall and fast skyrmions in the Inverse Heusler family
Skyrmions are magnetic excitations that are potentially ultrasmall and topologically protected, making them interesting for high-density all-electronic ultrafast storage applications. While recent experiments have confirmed the existence of various types of skyrmions, their typical sizes are much larger than traditiona...
1901.09446v1
2019-04-03
Observation of Topological Hall Effect and Signature of Room Temperature Antiskyrmions in Mn-Ni-Ga D2d Heusler magnets
Topologically stable nontrivial spin structures, such as skyrmions and antiskyrmions, display a large topological Hall effect owing to their quantized topological charge. Here, we present the finding of a large topological Hall effect beyond room temperature in the tetragonal phase of a Mn-Ni-Ga based ferrimagnetic Heu...
1904.01894v1
2019-04-25
Low damping magnetic properties and perpendicular magnetic anisotropy with strong volume contribution in the Heusler alloy Fe1.5CoGe
We present a study of the dynamic magnetic properties of TiN-buffered epitaxial thin films of the Heusler alloy Fe$_{1.5}$CoGe. Thickness series annealed at different temperatures are prepared and the magnetic damping is measured, a lowest value of $\alpha=2.18\times 10^{-3}$ is obtained. The perpendicular magnetic ani...
1904.11247v1
2018-02-17
FeTaSb and FeMnTiSb as promising thermoelectric materials: An ab initio approach
Thermoelectricity in principle provides a pathway to put waste heat to good use. Motivated by this we investigate thermal and electrical transport properties of two new Fe-based Heusler alloys, FeTaSb and FeMnTiSb, by a first principles approach and semiclassical Boltzmann transport theory within the constant relaxatio...
1802.06254v1
2018-12-13
Current-induced nucleation and dynamics of skyrmions in a Co-based Heusler alloy
We demonstrate room-temperature stabilization of dipolar magnetic skyrmions with diameters in the range of $100$ nm in a single ultrathin layer of the Heusler alloy Co$_2$FeAl (CFA) under moderate magnetic fields. Current-induced skyrmion dynamics in microwires is studied with a scanning Nitrogen-Vacancy magnetometer o...
1812.05345v1
2020-04-03
Improved magnetostructural and magnetocaloric reversibility in magnetic Ni-Mn-In shape-memory Heusler alloy by optimizing the geometric compatibility condition
We report an improved reversibility of magnetostriction and inverse magnetocaloric effect (MCE) for the magnetic shape-memory Heusler alloy Ni$_{1.8}$Mn$_{1.8}$In$_{0.4}$. We show that the magnetostriction and MCE crucially depends on the geometrical compatibility of the austenite and martensite phases. Detailed inform...
2004.01527v1
2020-08-17
Interaction between skyrmions and antiskyrmions in a coexisting phase of a Heusler material
Coexisting phases of magnetic skyrmions and antiskyrmions have proposed to exhibit a variety of fascinating properties, owing to interactions between them. The recent discovery of the coexisting phase in a Heusler material could offer a platform for skyrmion-antiskyrmion-based spintronics. Here we report Lorentz electr...
2008.07272v2
2016-03-10
Pairing of j=3/2 fermions in half-Heusler superconductors
We theoretically consider the superconductivity of the topological half-Heusler semimetals YPtBi and LuPtBi. We show that pairing occurs between j=3/2 fermion states, which leads to qualitative differences from the conventional theory of pairing between j=1/2 states. In particular, this permits Cooper pairs with quinte...
1603.03376v3
2016-03-27
Thermoelectric properties of half-Heusler $\mathrm{ZrNiPb}$ by using first principles calculations
We investigate electronic structures and thermoelectric properties of recent synthetic half-Heusler $\mathrm{ZrNiPb}$ by using generalized gradient approximation (GGA) and GGA plus spin-orbit coupling (GGA+SOC). Calculated results show that $\mathrm{ZrNiPb}$ is a indirect-gap semiconductor. Within the constant scatteri...
1603.08203v1
2016-03-28
Ab initio Studies on Electronic and Magnetic Properties of X$_{2}$PtGa (X = Cr, Mn, Fe, Co) Heusler Alloys
Using first-principles calculations based on density functional theory, we probe the electronic and magnetic properties of X$_{2}$PtGa (X being Cr, Mn, Fe, Co) Heusler alloys. Our calculations predict that all these systems possess inverse Heusler alloy structure in their respective ground states. Application of tetrag...
1603.08350v2
2019-08-20
Coexistence of spin frustration and spin unfrustration induced spontaneous exchange bias in Heusler alloys
The mechanism of spontaneous exchange bias (SEB) and the dominant factor of its blocking temperature are still unclear in Heusler alloys. Here, the related investigations are performed in Mn2Ni1.5Al0.5 Heusler alloys with SEB. The results of both magnetic measurements and first-principles calculations confirmed that sp...
1908.07149v1
2019-12-23
Peculiarities of electronic transport and magnetic state in half-metallic ferromagnetic and spin gapless semiconducting Heusler alloys
A brief survey of experimental and theoretical studies of half-metallic ferromagnets (HMFs) and spin gapless semiconductors is given, the possible candidates being the X$_2$YZ (X = Mn, Fe, Co; Y = Ti, V, Cr, Mn, Fe, Co, Ni; Z = Al, Si, Ga, Ge, In, Sn, Sb) Heusler alloys. The data on the electrical resistivity, normal a...
1912.10771v1
2020-03-20
A ternary map of Ni-Mn-Ga Heusler alloys from ab initio calculations
In the present work, the aspects of magnetic and structural properties of Ni-Mn-Ga alloys are described in the framework of fist-principles approach and mapped into ternary composition diagrams. The stable atomic arrangement and magnetic alignment for compositions with cubic austenite and tetragonal martensite structur...
2003.09128v1
2020-06-05
Anomalous dependence of thermoelectric parameters on carrier concentration and electronic structure in Mn-substituted Fe2CrAl Heusler alloy
We investigate the high temperature thermoelectric properties of Heusler alloys Fe2-xMnxCrAl (0<x<1). Substitution of 12.5% Mn at Fe-site (x = 0.25) causes a significant increase in high temperature resistivity (\r{ho}) and an enhancement in the Seebeck coefficient (S), as compared to the parent alloy. However, as the ...
2006.03234v2
2020-09-24
Electronic Structure and Thermoelectric Properties of Half-Heusler Alloys NiTZ
We have investigated the electronic and thermoelectric properties of half-Heusler alloys NiTZ (T = Sc, and Ti; Z = P, As, Sn, and Sb) having 18 valence electron. Calculations are performed by means of density functional theory and Boltzmann transport equation with constant relaxation time approximation, validated by Ni...
2009.11916v4
2020-12-22
Structural insight using anomalous XRD into Mn2CoAl Heusler alloy films grown by magnetron sputtering, IBAS and MBE techniques
Inverse Heusler alloy Mn2CoAl thin films, known as a spin-gapless semiconductor (SGS), grown by three different methods: ultra-high vacuum magnetron spattering, Ar-ion beam assisted sputtering, and molecular beam epitaxy, are investigated by comparing their electric transport properties, microstructures and atomic-leve...
2012.12282v1
2021-02-01
Electronic, magnetic and galvanomagnetic properties of Co-based Heusler alloys: possible states of a half-metallic ferromagnet and spin gapless semiconductor
Parameters of the energy gap and, consequently, electronic, magnetic and galvanomagnetic properties in different X$_2$YZ Heusler alloys can vary quite strongly. In particular, half-metallic ferromagnets (HMFs) and spin gapless semiconductors (SGSs) with almost 100% spin polarization of charge carriers are promising mat...
2102.00952v1
2021-04-22
Chemical bonding origin of the thermoelectric power factor in Half-Heusler semiconductors
Intermetallic semiconductors with the cubic Half-Heusler structure (XYZ) have excellent thermoelectric properties. This has been attributed to the high degeneracy of the carrier pockets in the band structure, but large differences are found between different material compositions. Half-Heuslers are often interpreted wi...
2104.11281v1
2021-05-11
First-principles calculations and experimental studies on Co2FeGe Heusler alloy nanoparticles for spintronics applications
Here, we report the synthesis and physical properties of Co2FeGe (CFG) Heusler alloy (HA) nanoparticles (NPs). The NPs of size 23 nm are prepared using the co-precipitation method. X-ray and selected area electron diffraction patterns have confirmed the cubic Heusler phase of the NPs with the A2-disorder. These NPs are...
2105.05200v1
2021-09-23
Tuning magnetic antiskyrmion stability in tetragonal inverse Heusler alloys
The identification of materials supporting complex, tunable magnetic order at ambient temperatures is foundational to the development of new magnetic device architectures. We report the design of Mn2XY tetragonal inverse Heusler alloys that are capable of hosting magnetic antiskyrmions whose stability is sensitive to e...
2109.11423v1
2021-09-24
Impact of local arrangement of Fe and Ni on the phase stability and magnetocrystalline anisotropy in Fe-Ni-Al Heusler alloys
On the basis of density functional calculations, we report on a comprehensive study of the influences of atomic arrangement and Ni substitution for Al on the ground state structural and magnetic properties for Fe$_2$Ni$_{1+x}$Al$_{1-x}$ Heusler alloys. We discuss systematically the competition between five Heusler-type...
2109.12005v2
2023-09-06
Development of a self-consistent thermodynamically optimized database along with phase transition experiments in Ni-Mn-Ga system for magnetocaloric applications
Magnetocaloric materials have received significant attention of research community as they can minimize the use of harmful gases (CFCs, HFCs) and render eco-friendly refrigeration. Heusler alloys (Ni2MnGa) are known for their magnetocaloric effects, which make them useful as energy efficient and eco-friendly refrigerat...
2309.02694v1
2024-03-12
Ferrimagnetic Heusler tunnel junctions with fast spin-transfer torque switching enabled by low magnetization
Magnetic random access memory that uses magnetic tunnel junction memory cells is a high performance, non-volatile memory technology that goes beyond traditional charge-based memories. Today its speed is limited by the high magnetization of the memory storage layer. Here we show that fast and highly reliable switching i...
2403.08112v1
2023-02-22
Influence of Gd-rich precipitates on the martensitic transformation, magnetocaloric effect and mechanical properties of Ni-Mn-In Heusler alloys -- A comparative study
A multi-stimuli cooling cycle can be used to increase the cyclic caloric performance of multicaloric materials like Ni-Mn-In Heusler alloys. However, the use of a uniaxial compressive stress as an additional external stimulus to a magnetic field requires good mechanical stability. Improvement of mechanical stability an...
2302.11439v1
2008-10-29
Thermodynamics of the Heusler alloy Co_2-xMn_1+xSi: a combined density functional theory and cluster expansion study
Previous studies indicated that intrinsic point defects play a crucial role for the density of states of ferromagnetic half-metals in the band gap region: At large concentrations, defect-derived bands might close the gap at the Fermi energy in the minority spin channel. In this work, structural disorder in the Co- and ...
0810.5354v2
2014-10-01
Spin gapless semiconducting behavior in equiatomic quaternary CoFeMnSi Heusler alloy
Spin gapless semiconductors (SGS) form a new class of magnetic semiconductors, which has a band gap for one spin sub band and zero band gap for the other, and thus are useful for tunable spin transport based applications. In this paper, we report the first experimental evidence for spin gapless semiconducting behavior ...
1410.0177v1
2016-08-09
Compensated ferrimagnetic tetragonal Heusler thin films for antiferromagnetic spintronics
In recent years, antiferromagnetic spintronics has received much attention since ideal antiferromagnets do not produce stray fields and are much more stable to external magnetic fields compared to materials with net magnetization. Akin to antiferromagnets, compensated ferrimagnets have zero net magnetization but have t...
1608.02887v1
2018-09-20
Surface Majorana Flat Bands in $j=\frac{3}{2}$ Superconductors with Singlet-Quintet Mixing
Recent experiments have revealed the evidence of nodal-line superconductivity in half-Heusler superconductors, e.g. YPtBi. Theories have suggested the topological nature of such nodal-line superconductivity and proposed the existence of surface Majorana flat bands on the (111) surface of half-Heusler superconductors. D...
1809.07455v2
2019-11-12
Formation and magnetic properties of spark plasma sintered Mn$_{3-δ}$ ($δ$ = 0, 1) alloys
We present the synthesis of D0$_{22}$ Mn$_{3 - \delta}$Ga ($\delta$ = 0, 1) Heusler alloys by Spark Plasma Sintering method. The single phase Mn$_3$Ga (T$_\mathrm{c}$ $\simeq$ 780 K) is synthesized, while Mn$_2$Ga (T$_\mathrm{c}$ $\simeq$ 710 K) is found to coexist with a near-stoichiometric room temperature paramagnet...
1911.05040v1
2021-07-19
Impact of local arrangement of Fe and Ni in Fe-Ni-Al Heusler alloys on the phase stability and magnetocrystalline anisotropy
On the basis of the density functional calculations in combination with the supercell approach, we report on a complete study of the influences of atomic arrangement and Ni substitution for Al on the ground state structural and magnetic properties for Fe$_2$Ni$_{1+x}$Al$_{1-x}$ Heusler alloys. We discuss systematically...
2107.08804v2
2019-03-11
Evidence for the formation of nanoprecipitates with magnetically disordered regions in bulk $\mathrm{Ni}_{50}\mathrm{Mn}_{45}\mathrm{In}_{5}$ Heusler alloys
Shell ferromagnetism is a new functional property of certain Heusler alloys which has been recently observed in $\mathrm{Ni}_{50}\mathrm{Mn}_{45}\mathrm{In}_{5}$. We report the results of a comparative study of the magnetic microstructure of bulk $\mathrm{Ni}_{50}\mathrm{Mn}_{45}\mathrm{In}_{5}$ Heusler alloys using ma...
1903.04183v1
2020-03-25
Establishing the carrier scattering phase diagram for ZrNiSn-based half-Heusler thermoelectric materials
Chemical doping is one of the most important strategies for tuning electrical properties of semiconductors, particularly thermoelectric materials. Generally, the main role of chemical doping lies in optimizing the carrier concentration, but there can potentially be other important effects. Here, we show that chemical d...
2003.11222v3
2020-06-03
Half-Heusler thermoelectric materials: NMR studies
We report $^{59}$Co, $^{93}$Nb, and $^{121}$Sb nuclear magnetic resonance (NMR) measurements combined with density functional theory (DFT) calculations on a series of half-Heusler semiconductors, including NbCoSn, ZrCoSb, TaFeSb and NbFeSb, to better understand their electronic properties and general composition-depend...
2006.02013v1
2020-11-06
Thermoelectric power factor under strain-induced band-alignment in the half-Heuslers NbCoSn and TiCoSb
Band convergence is an effective strategy to improve the thermoelectric performance of complex bandstructure thermoelectric materials. Half-Heuslers are good candidates for band convergence studies because they have multiple bands near the valence bad edge that can be converged through various band engineering approach...
2011.04288v1
2021-05-05
Rhodium based half-Heusler alloys as possible optoelectronic and thermoelectric materials
On the basis of density functional theory and semi-classical Boltzmann theory, we have investigated the structural, elastic, electronic, optical and thermoelectric properties of 18--valence electron count rhodium based half-Heusler alloys focusing on RhTiP, RhTiAs, RhTiSb, and RhTiBi. The absence of imaginary frequenci...
2105.02177v1
2021-10-05
Tuning the Parity Mixing of Singlet-Septet Pairing in a Half-Heusler Superconductor
In superconductors, electrons with spin ${s=1/2}$ form Cooper pairs whose spin structure is usually singlet (${S=0}$) or triplet (${S=1}$). When the electronic structure near the Fermi level is characterized by fermions with angular momentum ${j=3/2}$ due to strong spin-orbit interactions, novel pairing states such as ...
2110.01819v2
2022-08-10
Defect engineering and Fermi-level tuning in half-Heusler topological semimetals
Three-dimensional topological semimetals host a range of interesting quantum phenomena related to band crossing that give rise to Dirac or Weyl fermions, and can be potentially engineered into novel quantum devices. Harvesting the full potential of these materials will depend on our ability to position the Fermi level ...
2208.05415v2
2023-03-08
Spin-valve nature and giant coercivity of a ferrimagnetic spin semimetal Mn$_2$IrGa
Spin semimetals are amongst the most recently discovered new class of spintronic materials, which exhibit a band gap in one spin channel and semimetallic feature in the other, thus facilitating tunable spin transport. Here, we report Mn$_2$IrGa to be a candidate material for spin semimetal along with giant coercivity a...
2303.04649v2
2017-01-28
Half-metallicity versus Symmetry in Pt, Ni and Co-based Half Heusler Alloys: A First-principles Calculation
Using first principles calculations based on density functional theory, we study the geometric, electronic, and magnetic properties of Pt, Ni and Co-based half Heusler alloys, namely, Pt$BC$, Ni$BC$ and Co$BC$ ($B$ = Cr, Mn and Fe; $C$ = Al, Si, P, S, Ga, Ge, As, Se, In, Sn, Sb and Te). We calculate the formation energ...
1701.08282v2
2014-06-03
Phase coexistence and interrupted 1st order transition in magnetic shape memory alloys
Current theoretical studies on structural and magnetic properties of functional Ni-Mn-Z (Z = Ga, In, Sn) Heusler alloys address the origin of the structural transition from the austenite to martensite, and also address the dominant contribution to the latent heat associated with this magneto-structural transition. This...
1406.0627v1
2022-10-25
Conventional Half-Heusler Alloys Advance State-of-the-Art Thermoelectric Properties
Half-Heusler (HH) phases have garnered much attention as thermally stable and non-toxic thermoelectric materials for power conversion. The most studied alloys to date utilize Hf, Zr, and Ti as the base components. These alloys can achieve a moderate dimensionless figure of merit, ZT, near 1. Recent studies have advance...
2210.13949v1
2024-02-08
Inflation and Isotropization in Quintom Cosmology
This paper studies inflation and isotropization in the quintom model in the Bianchi I, Bianchi III, and Kantowski-Sachs backgrounds. First, we investigate inherent properties and generalize Heusler's proposition. Then by the use of the dynamical system approach, we consider the system in multiplicative and collective m...
2402.05454v1
2015-07-05
k-bitransitive and compound operators on Banach spaces
In this this paper, we introduce new classes of operators in complex Banach spaces, which we call k-bitransitive operators and compound operators to study the direct sum of diskcyclic operators. We create a set of sufficient conditions for k-bitransitivity and compound. We show the relation between topologically mixing...
1507.01166v1