half-Heusler Alloys Research Articles

Exploring the electronic and magnetic properties of half-heusler alloy CoMnSb: implications for spintronics

Heusler alloys have caught a lot of attention because they can be really useful in modern technology. In this study, we investigated the electronic and magnetic properties of CoMnSb by employing advanced computational methods rooted in Density functional theory and plane-wave pseudo potential approach. Our investigation uncovers that CoMnSb is a half-metallic ferromagnet with a half-metallic gap of 0 eV at the equilibrium lattice constant. The total spin magnetic moments have been computed 3µB per unit cell which is in good agreement with the slater pauling rule Mt = Zt − 18 for Half Heusler alloy. The hybridization of the eg and t2g orbitals of the Co, Mn,and P-orbitals of the Sb are primarily responsible for the band gap. This indicates that these alloys hold great potential as functional materials for spintronics.

First Principles Studies on Structural, Elastic, Electronic, Optical Properties of MgSrPb and MgSrSi Half Heusler Alloys

First Principles Studies on Structural, Elastic, Electronic, Optical Properties of MgSrPb and MgSrSi Half Heusler Alloys

First-principles assisted design of high-entropy thermoelectric materials based on half-Heusler alloys

The deformation potential theory and semi-classical Boltzmann theory were combined to predict the thermoelectric performances of half-Heusler NaCuTe alloy and Li0.5Na0.5CuSe0.5Te0.5 high-entropy half-Heusler alloy through first-principles calculations. The former was constructed via the congener substitution method from LiCuSe alloy, while the latter was designed by the high-entropy engineering concept. The phonon spectrum and ab initio molecular dynamics simulations indicated that the three alloys display stable intermetallic compounds at ambient temperature. The electrical and thermal transport properties of p-type LiCuSe, NaCuTe, and Li0.5Na0.5CuSe0.5Te0.5 alloys were computed as a function of temperature and carrier concentration. The thermoelectric figure of merit for p-type Li0.5Na0.5CuSe0.5Te0.5 alloy was 1.005 and 3.443 at room temperature and 800 K, whereas that of p-type NaCuTe alloy achieved 2.488 at 800 K, which is obviously superior to most of the recently reported p-type half-Heusler thermoelectric materials. A comprehensive analysis of the phonon lifetime, Grüneisen parameters, phonon group velocities, and primitive cell phonon spectrum revealed that high-entropy engineering could introduce non-equivalent atoms and thus enhance phonon scattering, resulting in the reduction of lattice thermal conductivity. Furthermore, numerical simulations demonstrated that high-entropy engineering could improve the thermoelectric performances of half-Heusler alloys effectively, which provides a unique approach for the optimized design of novel thermoelectric materials.

Computational characterization of structural, electronic, elastic and magnetic properties of double half-Heusler alloy Fe2MnCoGe2

Using the augmented plane wave method based on density functional theory and implemented in the WIEN2k code, we study the structural, elastic, electronic, and magnetic properties of FeCoGe, FeMnGe, and the parent half-Heusler (HH) alloys, as well as their derivative Fe2CoMnGe2 double half-Heusler (DHH) compounds. By analysing the stability of the HH structure in both the ferromagnetic and non-magnetic phases of FeCoGe and FeMnGe alloys, we determine that the latter phase of type II and type III FeCoGe and FeMnGe arrangements is the most stable. The Fe2CoMnGe2 DHH alloy, which is derived from the magnetic and structural ground states of FeCoGe and FeMnGe HH alloys, is found to be most stable in the type II arrangement. Among these materials, the FeMnGe HH alloy demonstrates greater resistance to reversible deformation by shear strain, indicated by its higher Young's modulus, while FeCoGe shows the best overall resistance to deformation. The electronic structures of FeCoGe, FeMnGe, and Fe2CoMnGe2 compounds reveal metallic behavior in the spin-up channel and semiconducting behavior in the spin-down channel. Their half-metallic gaps are 0.437 (0.181) eV, 0.543 (0.224) eV, and 0.353 (0.035) eV, respectively, with Fe2CoMnGe2 DHH retaining half-metallicity despite a lower band gap. The total magnetic moments for FeCoGe, FeMnGe, and Fe2CoMnGe2 are found to be 3, 1, and 4 μB, respectively. Given their half-metallic properties, these alloys show potential as candidates for spintronic applications.

Unravelling the effect of strain on the electronic structure, elastic and thermoelectric properties of half-Heusler alloy CoHfSi

Abstract Before realizing any device’s actual application, it is necessary to understand the material’s performance through first-principles investigations. Most of the devices consist of nanomaterials, especially thin film-based ones, which are under strain due to a lattice mismatch. This occurs between the thin film of active material and the substrate on which the thin film is grown. This strain affects the material’s properties and overall device performance. In this work, we comprehensively explored strain engineering’s impact on the electronic and thermal transport characteristics of the CoHfSi half-Heusler alloy. Employing the self-consistent ultra-soft pseudo-potential method and generalized gradient approximation within a density functional framework, we investigated the effect of both isotropic- and tetragonal-type strains. Strains were applied in both compressive and tensile categories. A semiconducting ground state with an indirect band gap of 1.248 eV is found under 5% compressive isotropic strain, which reduces to 0.847 eV for 5% tensile strain under the same type. On the other hand, the semiconducting energy bandgap increases from 0.986 eV (for 5% compressive) to 1.217 eV (for 5% tensile) for tetragonal strain. The power factor increases with the increase in temperature. It obtains a maximum value of ≈2.4 × 1012 Wm−1K−1s−1 for −5% isotropic and +5% tetragonal strain, and around this doping level, a better TE efficiency can be achieved. A maximum and saturated value of zT at 300 K and beyond is estimated to be more than 3.5 and 3 for −2% and −1% isotropic strain, respectively. For +5% isotropic strain, the electronic fitness function attains a maximum ∼9 × 10−20 W5/3ms−1/3K−2 at 800 K, irrespective of strain type. All these results provide novel insights into the strain-induced effects on the electronic and thermoelectric properties of mechanically and thermodynamically stable CoHfSi at elevated temperatures. Apart from strain-induced modifications, optimum p-type doping can also increase the power factor, figure-of-merit, and electronic fitness function of these strained CoHfSi half-Heusler alloys, demonstrating them as a suitable and promising candidate for thermoelectric applications.

Probing the structural, electronic, magnetic, and optical properties of Zr(Fe/Mn)Al half-Heusler alloys for optoelectronic applications: A first-principles investigation

Probing the structural, electronic, magnetic, and optical properties of Zr(Fe/Mn)Al half-Heusler alloys for optoelectronic applications: A first-principles investigation

Study on the phase stability, mechanical and half-metallic properties of half-Heusler alloys FeMnZ (Z = Si, Ge and Sn)

Study on the phase stability, mechanical and half-metallic properties of half-Heusler alloys FeMnZ (Z = Si, Ge and Sn)

High-entropy-driven half-Heusler alloys boost thermoelectric performance

High-entropy-driven half-Heusler alloys boost thermoelectric performance

First-principles calculations to investigate structural, electronic, magnetic mechanical, and thermal properties of half-Heusler alloys CoYGe (Y = Mn, Fe): using GGA and GGA+U potentials

First-principles calculations to investigate structural, electronic, magnetic mechanical, and thermal properties of half-Heusler alloys CoYGe (Y = Mn, Fe): using GGA and GGA+U potentials

First-principles studies on the magnetic properties, exchange interactions and spin Hall conductivity of the half-Heusler alloy MgMnGe

This study presents first-principles estimates of the magnetic characteristics, exchange interactions and the spin Hall conductivity (SHC) of the half -Heusler alloy MgMnGe. Various configurations of spin-ordering are taken into consideration. It is discovered that MgMnGe has an antiferromagnetic ground state, with a degenerate in plane Néel vector. The Korringa-Kohn-Rostoker method has been used to calculate the Néel temperature and exchange interactions. The Néel temperature of this material obtained theoretically using mean field approximation is 447.2 K while the experimental reported value is largely higher than 300 K. The exchange interaction has been shown to be mostly mediated by the Mn1-Mn2 exchange. The spin Hall conductivity of MgMnGe is obtained by mapping the electronic structures to the Wannier basis via linear response theory. The spin Hall conductivity as a function of the Fermi level has been determined.

Predictions of new KTaSn half-Heusler compound for spintronic, thermoelectric and optoelectronic applications: A first-principles study

Structural, electronic, magnetic, elastic, optical, thermodynamic, and thermoelectric characteristics of KTaSn half-Heusler compound are investigated using density functional theory (DFT). GGA-mBJ approximation calculations showed a direct minority spin band gap energy of 1.28 eV and a spin polarization of 100 %. The calculated total magnetic moment and Curie temperature are 2 μB and 380 K respectively. Elastic constants study and formation energy calculation revealed that the material is mechanically and thermodynamically stable and has a ductile nature. 0ptical properties of KTaSn half-Heusler alloy were similarly investigated to highlight its potential for optoelectronic applications. Finally, utilizing Boltzmann's quasi-classical theory, transport properties were studied and yielded a high figure of merit ZT value of 0.62 indicating that the material is suitable for applications in thermoelectric devices.

Half-metallicity and thermoelectric performance: A multifaceted investigation of Zr-based half-Heusler alloys

This work employs the linearized augmented plane-wave (LAPW) method within the framework of density functional theory (DFT) to explore the structural, elastic, electronic, magnetic, and thermoelectric properties of the Zr-based half-Heusler alloys CoZrSn and CoZrPb. The exchange–correlation functional is treated using both the Perdew-Burke-Ernzerhof (GGA-PBE) generalized gradient approximation and the Tran-Blaha-modified Beck-Johnson (TB-mBJ) potential, as implemented in the WIEN2k software package. Our findings indicate that the investigated material exhibits mechanical stability, suggesting its potential for experimental synthesis. Furthermore, both CoZrSn and CoZrPb display half-metallic behavior consistent with Slater-Pauling’s rule, characterized by an integer magnetic moment of 1 μB. Electronic band structures and density of states calculations, employing the TB-mBJ approximation, confirm this half-metallic character. Notably, indirect band gaps of 0.52 eV and 0.69 eV are observed for CoZrSn and CoZrPb, respectively. To investigate thermoelectric properties, including the Seebeck coefficient (S), electrical conductivity (σ), thermal conductivity (κ), and figure of merit (ZT), the Boltzmann transport equations within the DFT framework were utilized. The calculated values for the figure of merit and Seebeck coefficient suggest that the CoZrX alloys hold promise for thermoelectric applications. Significantly, there is a lack of prior experimental or theoretical investigations on the CoZrX half-Heusler alloys. Consequently, our theoretical predictions regarding the structural, elastic, electronic, magnetic, and thermoelectric properties provide valuable insights that can be further validated through future experimental studies.

Systematic study of d0-d KYZ (Y = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Z = al, Ga, In, Si, Ge, Sn, Pb, P, As, Sb, Bi, S, Se, Te) Heusler alloys

The 126 half-Heusler alloys based on the KYZ (Y=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Z = Al, Ga, In, Si, Ge, Sn, Pb, P, As, Sb, Bi) in three different C1b structures (α, β and γ) have been investigated using Density Functional Theory. It was found that the α phase does not conserve cubic symmetry and its tetragonal ratio varies between 1.61 and 2.02. The α-type was shown to be energetically more favorable than the β and γ phases, which maintain cubic symmetry. Most of the studied phases were found to be mechanically unstable, but the 19 cubic phases were found to exhibit either semiconductor or half-metallic behavior with band gaps ranging between 0.48 and 3.18 eV. The calculated thermal lattice conductivity kL did not exceed 1.17 W/m·K, making these alloys promising as thermoelectric materials.

First-principles study of structural, elastic, mechanical, electronic, magnetic, optical, and thermoelectric properties of CoFeTe half-heusler alloy

Half-Heusler CoFeTe alloy is analyzed using Density Functional Theory (DFT) calculations based on the GGA-PBE and GGA + U approximations. The results reveal that CoFeTe was most stable in the β-phase with a ferromagnetic configuration. As determined by the density of states analysis, metallic behavior is observed for the GGA-PBE approximation, whereas a semi metallic nature is observed for the GGA + U approximation. Phonon dispersion, elastic, and mechanical analyses confirm the dynamical and mechanical stability of the alloy. The thermoelectric properties suggest that CoFeTe shows potential for thermoelectric applications, with an increasing Seebeck coefficient and power factor, reaching a ZT value of 0.2 at 800 K. These findings highlight the potential of CoFeTe for applications in thermoelectric devices.

Topological signatures of triply degenerate fermions in Heusler alloys: an ab initio study

Triply degenerate nodal point (TP) fermions, lacking elementary particle counterparts, have been theoretically anticipated as quasiparticle excitations near specific band crossing points constrained by distinct space-group symmetries instead of Lorentz invariance. Here, based onfirst-principlescalculations and symmetry analysis, we demonstrate the presence of TP fermions in Heusler alloys. Furthermore, we predict that these Heusler alloys are dynamically stable, exhibiting TP fermions along four distinctC3axes in the F-43m space group. We show thatα-LiCaPdSb harbours peculiar Fermi arcs and surface states on the (111) and (001) crystal facets, owing to the coexistence of threefold rotational and time reversal symmetry. More interestingly, a modest tensile strain can increase the distance of fermions along the Γ-Lhigh symmetric line by as much as 21.10%, which give rise to measurable Fermi arcs. Furthermore, we investigate non-trivial topological insulator phase inβ-LiCaPdSb, by changing the chemical environment through placing transition metal atoms at various Wyckoff positions. Theβ-LiCaPdSb harbour a semi-metallic nature, and by breaking cubic symmetry, it undergoes a transition from semi-metal to a non-trivial topological insulator. In addition, for the first time, rare-earth LaPtBi half-Heusler alloy is examined under strain to uncover multiple band inversions associated with the TP fermionic phase. The observed multiple band inversion is entirely unaffected by spin-orbit coupling. We show that the LaPtBi compound hosts TP fermions, which are linked to aZ2topological invariant. Remarkably, with clear band crossings and multiple band inversion, we point out the possibilities of the LaPtBi for displaying a rich topological phase diagram. Our work provides a prototype material platform for experimental detection through angle-resolved photoemission spectroscopy or scanning tunnelling spectroscopy and practical spintronic applications.

Unveiling half-metallic, thermoelectric and optoelectronic behavior of the new Heusler alloy RbCrZ (Z = Si, Ge): a DFT perspective

Abstract Utilizing the density functional theory (DFT) method, this study aims to predict with precision the structural, elastic, electronic, magnetic, thermoelectric, thermal, and optical properties of two recently discovered half-Heusler alloys, namely RbCrSi and RbCrGe. The exchange and correlation potential are accounted for using the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE) and the Tran–Blaha-modified Becke–Johnson exchange potential (TB-mBJ). Through structural analysis, it is observed that both RbCrSi and RbCrGe alloys exhibit energetic stability in a type-3 structure with a ferromagnetic (FM) state. Both alloys exhibit half-metallic properties and integer magnetic moments of 3 μB, following the Slater-Pauli rule. Additionally, elastic calculations confirm their mechanical stability and anisotropic ductile behavior. The quasi-harmonic Debye model (QHDM) is employed for calculating thermodynamic properties, while the BoltzTraP code, based on semi-classical Boltzmann theory (SCBT), is utilized for evaluating thermoelectric properties. Findings reveal that RbCrZ alloys (with Z = Si, Ge) exhibit high figure of merit (ZT) values nearing unity at highest temperature. Consequently, the newfound half-Heusler alloys RbCrSi and RbCrGe hold significant promise for applications in thermoelectricity and spintronic devices. This comprehensive analysis underscores the potential of these alloys in the realm of renewable energy applications.

First-principles investigation of electronic, magnetic, and optical properties of FeMnSb/GaZ (Z = As or P) interfaces

We systematically investigated the electronic, magnetic, and optical properties of the FeMnSb half-Heusler alloy, its (001) surface, and its interfaces with GaAs and GaP semiconductors by using first-principles calculations based on density functional theory. The bulk FeMnSb reveals its half-metallic ferrimagnetism with 100% spin-polarization. Extending this study to the (001) surface, we uncover distinct electronic and magnetic behaviors for Fe- and MnSb-terminated surfaces, the MnSb-terminated surface preserving the half-metallicity observed in the bulk material. Our evaluation of the interfaces exhibits positive work of separation, indicating that these interfaces are energetically favorable. The density of states analysis reveals that all interfaces exhibit a metallic nature. High spin-polarization values, particularly 97.316% for the Fe-Ga interface, suggest a substantial degree of spin-polarized current. Notably, the absorption coefficient peaks shift from the ultraviolet (UV) region in the bulk alloy to the visible region at the (001) surfaces. However, at the FeMnSb/GaAs and FeMnSb/GaP interfaces, the highest absorption peaks revert to the UV region, highlighting strong interfacial coupling effects. These results suggest the tunability of FeMnSb optical properties via surface termination and interface engineering, making it a promising candidate for spintronic and optoelectronic applications.

Theoretical Insights into Off-Stoichiometric Zr(x)Ti(1-x)IrSb Half-Heusler Alloys: A First Principle Calculations.

This study presents a theoretical investigation into the phase stability, electronic, and optical properties of off-stoichiometric Zr_{x}Ti_{1-x}IrSb (x = 0, 0.0625, 0.1875, 0.25, 0.50, 0.75, 1) compounds. Using first-principles calculations, we explore how varying Zr and Ti concentrations can tune the electronic and optical properties of these half-Heusler alloys. The Structural, optical, and electronic properties were meticulously analyzed with both the GGA-PBE and Meta-GGA-SCAN approximations, as implemented in the Vienna Ab initio Simulation Package (VASP). The dynamical stability of these compounds was assessed using the Phonopy package. Our findings reveal that these alloys exhibit semiconductor behavior with tunable band gaps, and their optical properties show significant variation across different compositions, particularly in the visible light range. The compounds also demonstrate robust dynamical stability, indicating their potential for practical applications in electronic and optoelectronic devices. These results underscore the versatility of Zr_{x}Ti_{1-x}IrSb alloys and highlight their promise for next-generation technology.

Ferrimagnetic half metals TaMnZ (Z = As, Sb, Bi) for thermoelectric and spintronic applications – Material computations

Half metals possess coupling behavior of metals and semiconductors with wide heat transport and spin transport properties. This research article covers the structural, mechanical, electronic, magnetic and thermoelectric properties of the half Heusler alloys TaMnZ (Z = As, Sb, Bi). The equilibrium lattice constants and corresponding ground state energies show that the studied alloys are stable in the ferrimagnetic cubic phase. The band dispersion plots suggest that the compounds TaMnAs, TaMnSb and TaMnBi are half metals with indirect band gap having the band gap energies of 1.13 eV, 1.24 eV and 1.12 eV respectively in the spin down channel. As the materials have 100 % spin polarization with an integer magnetic moment of −1 μB, they are suitable for making spintronic devices such as spin transistors and spin-flip flops. The temperature-dependent thermoelectric properties of the alloys have been studied by classical Boltzmann theory. The materials have low lattice thermal conductivity which was confirmed by Slack’s equation. The obtained thermoelectric figure of merit for p-type TaMnAs, TaMnSb and TaMnBi is 0.7, 0.6 and 0.8 respectively at 1200 K. Similarly, the figure of merit obtained for n-type TaMnAs, TaMnSb and TaMnBi is 0.6, 0.64 and 0.8 respectively at the same temperature. The favourable heat and spin transport properties of these alloys show that they are the potential characters to figure out better thermoelectric and spintronic performance.

DFT study of structural, electronic, magnetic, elastic, and thermoelectric properties of Ta-based half-Heusler alloys CsTaX (X = C, Si, and Ge) for spintronics and thermoelectric technologies

The structural, electronic, elastic, magnetic, and thermoelectric characteristics of three novel Ta-based half-Heusler alloys, CsTaC, CsTaSi, and CsTaGe, have been investigated using the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method within the density functional theory (DFT). The volume-optimization graphs show that all compounds are stable in the ferromagnetic (FM) phase. Half-Metallicity of these compounds is confirmed by the density of states (DOS) and band structures. The total magnetic moment for CsTaC is 6 μB, and for CsTaX (X = Si, Ge) is 2 μB. The negative pd exchange energy and exchange constants confirm ferromagnetism. The values of Pugh’s ratio (B/G) and Poisson’s ratio (v) reveal that CsTaC is ductile and CsTaX (Si, Ge) is brittle. The thermoelectric response is estimated using the BoltzTraP code, demonstrating that at room temperature, maximum ZT values for CaTaC, CsTaSi, and CsTaGe are 0.99, 0.97, and 0.90, respectively. Consequently, CsTaX (X = C, Si, and Ge) are suitable candidates for spintronic and thermoelectric technologies.