full-Heusler Compounds Research Articles

Nodal-line symmetry breaking induced colossal anomalous Hall and Nernst effects in Cu2CoSn Heusler compound

The presence of topological band crossings near the Fermi energy is essential for the realization of large anomalous transport properties in the materials. The topological semimetals host such properties owing to their unique topological band structure, such as Weyl points or nodal lines (NLs), those are protected by certain symmetries of the crystal. When the NLs break out in the system, a large Berry curvature arises in the surrounding area of the gapped NL. In the present work, we studied anomalous transport properties of Cu2CoSn compound, which has a cubic Heusler crystal structure (space group: Fm3¯m). Cu2CoSn full Heusler compound possesses NLs at the Fermi level that is protected by mirror reflection symmetries of the lattice. Upon introducing the spin–orbit coupling in the Hamiltonian and by setting the magnetization axis along the [001] direction, we found that the NLs are gapped out and large Berry curvature arises in the system. The integral of Berry curvature gives the intrinsic anomalous Hall conductivity (AHC) about 1003 S/cm and the anomalous Nernst conductivity (ANC) about 3.98 A/m K at the Fermi level. These values of AHC and ANC are comparable to the largest reported values for the Co2MnGa Heusler compound. Therefore, Cu2CoSn becomes a newborn member of the family of full Heusler compounds, which possesses giant AHC and ANC that can be useful for the spintronics application.

First-Principles Studies on Spin-Dependent Transport of Magnetic Junctions with Half-Metallic Heusler Compounds

Two types of magnetoresistance (MR), i.e., tunnel magnetoresistance (TMR) and current perpendicular to plane giant magnetoresistance (CPP-GMR), are theoretically discussed for systems with half-metallic (HFM) Co-based full Heusler compounds. In TMR, the non-collinear spin structure at the Co2MnSi(CMS)/MgO(001) interface that results from thermal spin fluctuations significantly reduced the TMR ratio at room temperature (RT). Enhancement of the exchange stiffness of CMS/MgO was essential to suppress the reduction in TMR at RT. Furthermore, it is proposed that inserting of a B2-CoFe layer between CMS and MgO is a promising way to enhance the interface exchange stiffness constant. In CPP-GMR, the interface spin asymmetry γ in the Valet-Fert model was essential to enhance GMR at RT, because the temperature dependence of γ in experiments was much larger than that of the bulk spin asymmetry β. I showed that the experimental CPP-GMR ratio increases with the decrease in the theoretical resistance-area product RPA, which is roughly consistent with the RP dependence of γ. This means that matching of the conductive channel between HMF and a non-magnetic metallic spacer is a key parameter to enhance γ. These findings will be very important for room temperature spintronics devices applied in future artificial intelligence hardware.

Electronic structure, magnetic and optical properties of the Ti2RuAl full-Heusler compound by a first-principles study

Electronic structure, magnetic and optical properties of the Ti2RuAl full-Heusler compound by a first-principles study

First-Principles Calculations to Investigate the Stability and Thermodynamic Properties of a Newly Exposed Lithium-Gallium-Iridium-Based Full-Heusler Compound.

The structural, optical, electrical, thermodynamic, superconducting, and mechanical characteristics of LiGa2Ir full-Heusler alloys with the MnCu2Al configuration were comprehensively examined in this work using the first-principles computation approach premised upon density functional analysis. This theoretical approach is the first to investigate the influence of pressure on the mechanical and optical characteristics of LiGa2Ir. The structural and chemical bonding analysis shows that hydrostatic pressure caused a decrease in the lattice constant, volume, and bond length of each cell. According to the mechanical property calculations, the LiGa2Ir cubic Heusler alloy exhibits mechanical stability. It also has ductility and anisotropic behavior. This metallic substance shows no band gap throughout the applied pressure range. The physical characteristics of the LiGa2Ir full-Heusler alloy are analyzed in the operating pressure range of 0-10 GPa. The quasi-harmonic Debye model is employed to analyze thermodynamic properties. The Debye temperature (291.31 K at 0 Pa) increases with hydrostatic pressure. A newly invented structure attracted a lot of attention around the globe for its superior superconductivity (Tc ∼ 2.95 K). Optical functions have also been improved after applying stress to utilize it in optoelectronic/nanoelectric devices. The optical function analysis is supported strongly by the electronic properties. Due to these reasons, LiGa2Ir imposed an essential guiding principle for relevant future research and could be a credible candidate substance for industrial settings.

Theoretical pursuit of structural, mechanical, magneto-electronic, and thermoelectric features of new inverse full Heusler compounds Rb2ZrZ (Z = C, Si, Ge, and Sn). A first-principles investigation

Theoretical pursuit of structural, mechanical, magneto-electronic, and thermoelectric features of new inverse full Heusler compounds Rb2ZrZ (Z = C, Si, Ge, and Sn). A first-principles investigation

Structural, Elastic, Electronic, and Magnetic Properties of Full-Heusler Alloys Sc2TiAl and Sc2TiSi Using the FP-LAPW Method

In this article, the structural, elastic, electronic, and magnetic characteristics of both regular and inverse Heusler alloys, Sc2TiAl and Sc2TiSi, were investigated using a full-potential, linearized augmented plane-wave (FP-LAPW) method, within the density functional theory. The optimized structural parameters were determined from the minimization of the total energy versus the volume of the unit cell. The band structure and DOS calculations were performed within the generalized gradient approximation (GGA) and modified Becke–Johnson approaches (mBJ-GGA), employed in the Wien2K code. The density of states (DOS) and band structure (BS) indicate the metallic nature of the regular structure of the two compounds. The total spin magnetic moments for the two compounds were consistent with the previous theoretical results. We calculated the elastic properties: bulk moduli, B, Poisson’s ratio, ν, shear modulus, S, Young’s modulus (Y), and the B/s ratio. Additionally, we used Blackman’s diagram and Every’s diagram to compare the elastic properties of the studied compounds, whereas Pugh’s and Poisson’s ratios were used in the analysis of the relationship between interatomic bonding type and physical properties. Mechanically, we found that the regular and inverse full-Heusler compounds Sc2TiAl and Sc2TiSi were stable. The results agree with previous studies, providing a road map for possible uses in electronic devices.

Nodal-line and triple point fermion induced anomalous Hall effect in the topological Heusler compound Co2CrGa

Magnetic topological semimetals have interesting anomalous behavior and can be manipulated by tuning the symmetry-protected nodal crossings. ${\mathrm{Co}}_{2}$-based full Heusler compounds serve as a fertile playground where various novel topological properties can be investigated. In this paper, we present a systematic investigation of the anomalous Hall effect (AHE) in the ferromagnetic Heusler compound ${\mathrm{Co}}_{2}\mathrm{CrGa}$ using combined experimental and theoretical studies. The anomalous Hall resistivity ${\ensuremath{\rho}}_{yx}^{A}$ is observed to scale nearly quadratically with the longitudinal resistivity ${\ensuremath{\rho}}_{xx}$, and further experimental analysis suggests that the AHE in ${\mathrm{Co}}_{2}\mathrm{CrGa}$ should be dominated by the intrinsic Karplus-Luttinger Berry phase mechanism. Experimental results also reveal that the anomalous Hall conductivity (AHC) is as large as $\ensuremath{\sim}569$ S/cm at 10 K with an intrinsic contribution of $\ensuremath{\sim}526$ S/cm and the observed AHC is nearly temperature independent. In addition to the large AHC, we also found an exceptionally large anomalous Hall angle of $\ensuremath{\sim}8.5$% and a large anomalous Hall factor of $\ensuremath{\sim}0.23 {\mathrm{V}}^{\ensuremath{-}1}$ simultaneously at room temperature. First-principles calculations suggest that the Berry curvature originates from a gapped nodal line and that Weyl nodes which are generated from the triple point near the Fermi level ${E}_{F}$ in the presence of spin-orbit coupling are responsible for the observed large AHC in this compound.

Topologically nontrivial phase in Na2CuX (X= As, Sb, Sn and Bi) full Heusler compounds: Insights from DFT-based computer simulation

The inspection of materials supporting topological excitations is one of the prospective areas of condensed matter physics. This paper is devoted to studying the possibility of the existence of topological phases in Na2CuX (X= As, Sb, Sn and Bi) full Heusler compounds using the FP-LMTO (Full-Potential Linear Muffin-Tin Orbital) method with and without spin-orbit coupling (SOC). The study of structural properties has found that these materials are energetically stable in the Hg2CuTi type structure. Also, formation energy calculations have shown that these materials are convenient to manufacture. Otherwise, band structure calculations show that these materials exhibit the behavior of non-trivial topological materials with a semi-metallic nature. The obtained results in this study, generally, showed that SOC is not a primary cause of the band inversion mechanism.

Transport and thermoelectric properties of strongly anharmonic Full-Heusler compounds CsK2M (M=As, Bi)

Transport and thermoelectric properties of strongly anharmonic Full-Heusler compounds CsK2M (M=As, Bi)

First-principles calculations to investigate electronic, magnetic and half-metallic ferromagnetic properties of full-Heusler Mn2OsSn

ABSTRACT The structural, electrical, magnetic, and elastic characteristics of the Mn2OsSn full-Heusler compound have all been studied using the full potential linearised augmented plane (FP-LAPW) method. The study's exchange and correlation potentials are calculated using the generalised gradient approach (GGA) developed by Burke, Perdew, and Ernzerhof; the GGA with the Tran-Blaha-modified Becke–Johnson approximations; and the GGA with the correlated Hubbard parameter (GGA +U). Our calculations show that the formation energy of the compound is negative for the two-type structure, which means the crystal may persist indefinitely. Our chemical has a convex hull distance at 0 K for cubic regular and inverse-type structures, indicating that it will likely be synthesised via equilibrium processing. The electronic band structures, densities of states, and 100 spin-polarisation at the Fermi level in the typical cubic AlCu2Mn-type structure show Mn2OsSn in its complete Heusler ferromagnetic state has a half-metallic feature with an indirect band gap in the minority spin. Alternatively, in the CuHg2Ti-type ferromagnetic state, with its inverse cubic structure, this material exhibits metallic ferromagnetic behaviour with a polarisation of 96,325. The half metallicity of the AlCu2Mn-type combination is preserved at 1 GPa of hydrostatic pressure. Thus, Mn2OsSn, with the appropriate correction option for the Hubbard-Coulomb parameter U, will be a promising contender for spintronic applications.

Strong quartic anharmonicity, ultralow thermal conductivity, high band degeneracy and good thermoelectric performance in Na2TlSb

We employ first-principles calculations combined with self-consistent phonon theory and Boltzmann transport equations to investigate the thermal transport and thermoelectric properties of full-Heusler compound Na2TlSb. Our findings exhibit that the strong quartic anharmonicity and temperature dependence of the Tl atom with rattling behavior plays an important role in the lattice stability of Na2TlSb. We find that soft Tl-Sb bonding and resonant bonding in the pseudocage composed of the Na and Sb atoms interaction is responsible for ultralow κL. Meanwhile, the multi-valley band structure increases the band degeneracy, results in a high power factor in p-type Na2TlSb. The coexistence of ultralow κL and high power factor presents that Na2TlSb is a potential candidate for thermoelectric applications. Moreover, these findings help to understand the origin of ultralow κL of full-Heusler compounds with strong quartic anharmonicity, leading to the rational design of full-Heusler compounds with high thermoelectric performance.

A DFT study of new full Heusler compound Li2MgC insights into the structural, electronic and thermoelectric properties: A high efficiency performance thermoelectric material

Structural, electronic and thermoelectric properties for full Heusler compound Li2MgC were studied using the full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT), implemented in the Wien2k package. The term of the exchange and correlation potential (XC) is treated by the generalized gradient approximation GGA and Trans-Blaha-modified Becke–Johnson (mBJ-GGA). From the various calculations, it emerges that the Cu2MnAl type structure is more suitable for this compound than that of the Hg2CuTi type structure; moreover, this compound is stable in the non-magnetic (NM) state. Furthermore, this compound exhibits a semi -conductor behavior with an indirect band gap at Γ-X direction. The calculated formation and cohesion energies are negative, which clearly and unequivocally indicates the thermodynamic stability of the compound studied and that it can be synthesized experimentally. Otherwise, this compound is characterized by a high figure of merit (ZT) (close to unity), making it a promising candidate for thermoelectric applications.

Half-metallic behavior Co2YAl (Y= Mo,Tc) compounds

The present manuscript reports structural stability, half-metallic behavior, thermophysical and thermoelectric properties of Co2MoAl and Co2TcAl full Heusler compounds using first-principle calculations. The full-potential linearized augmented plane wave method within the framework of density functional theory is implemented and WIEN2k code is incorporated in the stable Fm- 3m phase to attain the desired results. The L21 phase is found as the most stable phase for both compounds. The optimized equilibrium lattice parameters in the stable phase are 5.89Å, 5.86Å for Co2MoAl and Co2TcAl respectively. The electronic band structure study proves that both compounds Co2MoAl and Co2TcAl have indirect band gaps of 0.74eV and 0.85eV respectively in majority spin alignment. The half-metallic performance of the present set of compounds is explained by the spin-resolved density of states. The Fermi level at the Brillouin zone point approves the metallic as well as semiconducting behavior. To elucidate the thermodynamical stability of these materials against pressure and temperature by implementing the quasi-harmonic approximation of various parameters like Debye temperature, Gruneisen parameters and specific heat are studied successfully. To know the thermoelectric response, Seebeck coefficient and electrical conductivity are computed using the BoltzTrap code. The thermodynamic profile delivers that the present set of compounds possesses no anomalies with respect to the phase transition or instabilities. The computational study insights that the compounds can be synthesized experimentally and find a route towards spintronic and thermoelectric applicability.

Half-metallic behavior Co2YAl (Y= Mo,Tc) compounds

The present manuscript reports structural stability, half-metallic behavior, thermophysical and thermoelectric properties of Co2MoAl and Co2TcAl full Heusler compounds using first-principle calculations. The full-potential linearized augmented plane wave method within the framework of density functional theory is implemented and WIEN2k code is incorporated in the stable Fm- 3m phase to attain the desired results. The L21 phase is found as the most stable phase for both compounds. The optimized equilibrium lattice parameters in the stable phase are 5.89Å, 5.86Å for Co2MoAl and Co2TcAl respectively. The electronic band structure study proves that both compounds Co2MoAl and Co2TcAl have indirect band gaps of 0.74eV and 0.85eV respectively in majority spin alignment. The half-metallic performance of the present set of compounds is explained by the spin-resolved density of states. The Fermi level at the Brillouin zone point approves the metallic as well as semiconducting behavior. To elucidate the thermodynamical stability of these materials against pressure and temperature by implementing the quasi-harmonic approximation of various parameters like Debye temperature, Gruneisen parameters and specific heat are studied successfully. To know the thermoelectric response, Seebeck coefficient and electrical conductivity are computed using the BoltzTrap code. The thermodynamic profile delivers that the present set of compounds possesses no anomalies with respect to the phase transition or instabilities. The computational study insights that the compounds can be synthesized experimentally and find a route towards spintronic and thermoelectric applicability.

Effect of Mn Doping on the Electronic and Magnetic Properties of Full Heusler Alloy Co2FeSi

Heusler compounds are one of the largest families of ternary intermetallics with broad range of applications. In this work, we inspected the electronic and magnetic properties of full Heusler alloy Co2FeSi and the effect induced by doping Mn atom on those properties. We employed plane wave pseudo-potential method based on DFT framework implemented in Quantum ESPRESSO code using PBE type of functional for exchange correlation energy. The calculation demonstrates that Co2FeSi exhibits metallic nature in the majority spin state and semi-conducting nature in minority spin state with indirect energy gap of ≈ 0.132 eV and shows chances of weakened half-metallicity as indicated by the presence of band gap below fermi level. The calculated total magnetic moment is 5.44 μB/cell which is found to be deviated from Slater-Pauling rule M = NV − 24 for full Heusler compounds. The site selection for doping was based on the empirical rule for atomic occupation established for Heusler alloys and the calculation of formation energy. The calculation of formation energy at B and D site showed B site as more favorable for doping for both 25% and 50% concentration. At 25% Mn concentration, calculation shows Co2FeSi has typical metallic behavior for spin-up electrons, but semi-conducting behavior with decreased gap below fermi level for spin-down electrons showing no half-metallicity whereas for 50% Mn concentration the gap gets broadened by 0.089645 eV. The calculated magnetic moment for 25% and 50% Mn doping is 21.93 μB/cell and 21.69 μB/cell respectively. Our calculation depicts that the chances of half-metallicity decreases for 25% concentration of Mn atom and increases for 50% Mn concentration.

First-principles calculations to investigate structural stability, half-metallic behavior, thermophysical and thermoelectric properties of Co2YAl (Y = Mo, Tc) full Heusler compounds

The present manuscript reports structural stability, half-metallic behavior, thermophysical and thermoelectric properties of Co2MoAl and Co2TcAl full Heusler compounds using first-principle calculations. The full-potential linearized augmented plane wave method within the framework of density functional theory is implemented and WIEN2k code is incorporated in the stable Fm-3 m phase to attain the desired results. The L21 phase is found as the most stable phase for both compounds. The optimized equilibrium lattice parameters in the stable phase are 5.89 Å, 5.86 Å for Co2MoAl and Co2TcAl respectively. The electronic band structure study proves that both compounds Co2MoAl and Co2TcAl have indirect band gaps of 0.74 eV and 0.85 eV respectively in majority spin alignment. The half-metallic performance of the present set of compounds is explained by the spin-resolved density of states. The Fermi level at the Brillouin zone point approves the metallic as well as semiconducting behavior. To elucidate the thermodynamical stability of these materials against pressure and temperature by implementing the quasi-harmonic approximation of various parameters like Debye temperature, Gruneisen parameters and specific heat are studied successfully. To know the thermoelectric response, Seebeck coefficient and electrical conductivity are computed using the BoltzTrap code. The thermodynamic profile delivers that the present set of compounds possesses no anomalies with respect to the phase transition or instabilities. The computational study insights that the compounds can be synthesized experimentally and find a route towards spintronic and thermoelectric applicability.

Anomalous Hall effect in topological Weyl and nodal-line semimetal Heusler compound Co2VAl

Magnetic topological semimetals (TSMs) with broken time-reversal symmetry are very rare and have drawn significant attention in condensed matter physics due to their numerous intriguing topological properties. Among these various magnetic TSMs, Co2-based full Heusler compounds are of current interest, since a few of these materials exhibit Weyl and nodal fermions in their topological band structure. In this work, we report a comprehensive study of anomalous Hall effect (AHE) in the ferromagnetic full Heusler compound Co2VAl. Recent studies indicate that the intrinsic AHE is closely related to the Berry curvature of the occupied electronic Bloch states. The present study of Co2VAl attempts to understand and explore the possibility of topology-induced AHE. The anomalous Hall resistivity is observed to scale quadratically with the longitudinal resistivity ρ xx . Our experimental results also reveal that the anomalous Hall conductivity (AHC) is ∼85 cm−1 at 2 K with an intrinsic contribution of ∼75.6 S cm−1, and is nearly insensitive to temperature. The first principle calculations note that the Berry curvature originated from a gapped nodal line and symmetry-protected Weyl nodes near the Fermi level () is the main source of AHE in this compound. Thus, this investigation on Co2VAl discloses that it is a ferromagnetic Weyl and nodal-line TSM. The theoretically calculated AHC is in well agreement with the experimentally obtained AHC.

First-principles study of physical, and superconducting properties of newly discovered full-Heusler compound MgPd 2 Sb

A DFT-based theoretical technique is used to investigate the physical characteristics of type-II MgPd 2 Sb superconductor, which reveals superconductivity below 2.83 K. By using the McMillan equation, the computed electron-phonon coupling constant is 0.60. This suggests that this compound can be classified as a weakly coupled superconductor, which is consistent in accordance with earlier published theoretical as well as experimental results. The calculated lattice parameter, density of state (DOS) and Debye temperature are also consistent with other studies. The calculated electronic band structure indicates that the studied compound is metallic in nature. For the first time we have investigated the detailed optical and mechanical characteristics of MgPd 2 Sb superconductor. The computed elastic constant reveals that this compound is mechanically stable and ductile. The anisotropy of the MgPd 2 Sb superconductor is determined by using the Zener anisotropic algorithm and the ELATE code.The optical properties of this Heusler type superconductor are nearly similar to other members of the same family. We believe that the present findings can assist researchers in finding and analyzing new superconducting candidates among the full-Heusler alloys.

The Structural, Electronic, Magnetic and Elastic Properties of Full-Heusler Co2CrAl and Cr2MnSb: An Ab Initio Study

In this paper, the full-potential, linearized augmented plane wave (FP-LAPW) method was employed in investigating full-Heusler Co2CrA1’s structural, elastic, magnetic and electronic properties. The FP-LAPW method was employed in computing the structural parameters (bulk modulus, lattice parameters, c/a and first pressure derivatives). The optimized structural parameters were determined by generalized gradient approximation (GGA) for the exchange-correlation potential, Vxc. Estimating the energy gaps for these compounds was accomplished through modified Becke–Johnson potential (mBJ). It was found that the conventional Heusler compound Co2CrA1 with mBJ and CGA approaches had a half-metallic character, and its spin-down configuration had an energy gap. It was also found that the conventional and inverse Heusler Cr2MnSb and tetragonal (139) (Co2CrA1, Cr2MnSb) compounds with a half-metallic character had direct energy gaps in the spin-down configuration. To a certain degree, the total magnetic moments for the two compounds were compatible with the theoretical and experimental results already attained. Mechanically, we found that the conventional and inverse full-Heusler compound Co2CrAl was stable, but the inverse Cr2MnSb was unstable in the ferromagnetic state. The conventional Heusler compound Cr2MnSb was mechanically stable in the ferromagnetic state.

Ab initio calculation of the Hubbard U and Hund exchange J in local moment magnets: The case of Mn-based full Heusler compounds

Mn-based full Heusler compounds possess well-defined local atomic Mn moments, and thus the correlation effects between localized d electrons are expected to play an important role in determining the electronic and magnetic properties of these materials. Employing ab-initio calculations in conjunction with the constrained random-phase approximation (cRPA) method, we calculate the strength of the effective on-site Coulomb interaction parameters (Hubbard U and Hund exchange J) in the case of X2MnZ full Heusler compounds with X being one of Ni, Pd or Cu, and Z being one of In, Sn, Sb or Te. We show that the Z element (or sp element) in Heusler compounds significantly reduces the strength of the Hubbard U parameter for Mn 3d electrons compared to the elementary bulk Mn. On the contrary, the effect of the sp-atom on the strength of the U parameter of Ni, Cu or Pd valence d electrons is not so substantial with respect to the elementary bulk values. The U values for all transition metal atoms decrease with increasing sp electron number in the In-Sn-Sb-Te sequence. Our cRPA calculations reveal that despite their well-defined local magnetic moments, the Mn-based full Heusler alloys fall into the category of the weakly correlated materials.