Half-metallic Ferromagnets Research Articles

Interplay between Structural, Electronic, and Magnetic Properties in the p0-d Semi-Heusler Compounds: The Case of Li-Based Compounds

Half-metallic semi-Heusler compounds (also known as half-Heusler compounds) are currently at the forefront of scientific research due to their potential applications in spintronic devices. Unlike other semi-Heuslers, the p0(d0)-d compounds do not appear to crystallize in the typical variant of the C1b structure. We investigate this phenomenon in the p0-d Heusler compounds LiYGa and LiYGe, where Y varies between Ca and Zn, using first-principles ab initio electronic band-structure calculations. We examine the electronic and magnetic properties of these compounds in relation to the three possible C1b structures. Notably, LiVGa, LiVGe, LiMnGa, and LiCrGe are half-metallic ferromagnets across all three variations of the C1b lattice structure. Our findings will serve as a foundation for future experimental studies on these compounds.

Theoretical perspectives on the electronic, optical, mechanical, magnetic, and anisotropic behaviors of the quaternary Heusler alloys RhFeMnZ and IrMnCrZ (where Z = Si, Ge)

High-spin-polarised materials are the most promising candidates for spintronic devices. Here, the spin-polarised electronic structure, magnetism, mechanical, and optical properties of RhFeMnZ and IrMnCrZ (where Z = Si, Ge) Quaternary Heusler alloys were calculated by first-principles calculations. The calculations show that type III for the RhFeMnSi, RhFeMnGe, and IrMnCrSi and type I for the IrMnCrGe compound configuration is the most stable crystal structure for the studied alloys. The four alloys were found to have a half-metallic ferromagnetic structure with indirect band gaps in the majority spin channels of 0.957, 0.66, 0.745, and 0.891 eV for RhFeMnSi, RhFeMnGe, IrMnCrSi, and IrMnCrGe, respectively. They exhibit an appreciable total magnetic moment of 4 μB for RhFeMnZ (Z = Si, Ge) and 2 μB for IrMnCrZ (Z = Si, Ge). The results show that RhFeMnZ and IrMnCrZ (where Z = Si, Ge) are ferromagnetic half-metals with 100 % spin polarisation. The results of the elastic constants demonstrate the mechanical stability of RhFeMnZ and IrMnCrZ (where Z = Si, Ge) alloys. Optical properties such as dielectric function, absorption, reflectance, optical conductivity, and other optical properties were also probed. In the ultraviolet region, RhFeMnZ and IrMnCrZ (where Z = Si, Ge) are effective absorbers and have a high refractive index. Alloys are promising candidates for potential applications in spintronic devices.

Cr and Mn doping AgNbO3 for high Curie temperature ferromagnetic half-metals

The alterations in the electronic and magnetic properties of AgNbO3 induced by Cr and Mn doping at two concentrations (6% and 14%) are investigated within the framework of density functional theory (DFT), both with and without the Hubbard correction (U) as well as HSE method. Half-metallic ferromagnetic behavior with 100% polarization is observed for all dopants. Double exchange coupling is the mechanism responsible for the ferromagnetic interaction in these materials. Our results also indicates that the correction with U-term and HSE method provide consistent values that closely align with experimental measurements, and significantly improve the standard DFT description. Finally, the value of the Curie temperature, which reaches 425.49 (K), exceeds the ambient temperature, revealing the potential use of this doped material for new spintronic devices.

Determination of half metallicity behavior of quaternary heusler alloy crcoscga

In this work, the theoretical study through the calculations of the structural, electronic and magnetic properties of quaternary heusler compound CrCoScGa, using wien2k code, is reported. We adopted the generalized gradient approximation (GGA) to estimate the exchange correlation potential. The negative value of the formation energy shows that CrCoScGa compound have a high structural stability in the type III structure feromagnetic phase, so it can be experimentaly synthetised. According to our electronic calculations, CrCoScGa is a half-metallic ferromagnet (HMF) with a half-metallic gap of 0.22 eV. The total magnetic moment of 3µB, mainly originated from Cr and Co atoms, makes this alloy as a spintronic material.

Investigation of the structural, Electronic and magnetic properties of Mn2PdSn Heusler alloy under hydrostatic pressure

The pressure effect on the structural, electronic and magnetic properties of Mn2PdSn Heusler alloy was investigated by the first-principles full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). The exchange and correlation function has been chosen using generalized gradient approximation (GGA) within the parameterization of Perdew-burke-ernzerhof. The lattice constant, electronic density of state (DOS), and magnetic properties such as total magnetic moment were obtained under pressure. It was determined that the calculated lattice parameters are in good agreement with the literature. The Mn2PdSn is stable in the Hg2CuTi-type structure. Furthermore, we expect an extraordinary occurrence of pressure-induced metallic ferrimagnetism to half-metallic ferromagnetism transition in the cubic phase of Mn2PdSn alloy at hydrostatic pressures of 10 GPa.

Half-metallic ferromagneticWeyl fermions related to dynamic correlations in the zinc-blende compound VAs

Abstract The realization of 100% polarized topological Weyl fermions in halfmetallic ferromagnets is of particular importance for fundamental research and spintronic applications. Here, we theoretically investigate the electronic and topological properties of the zinc-blende compound VAs, which was deemed as a halfmetallic ferromagnet related to dynamic correlations. Based on the combination of density functional theory and dynamical mean field theory, we uncover that the halfmetallic ferromagnet VAs exhibit attractive Weyl semimetallic behaviors which are very close to the Fermi level in the DFT + U regime with effect U values ranging from 1.5 eV to 2.5 eV. Meanwhile, we also investigate the magnetization-dependent topological properties; the results show that the change of magnetization directions only slightly affects the positions of Weyl points, which is attributed to the weak spin-orbital coupling effects. The topological surface states of VAs projected on semiinfinite (001) and (111) surfaces are investigated. The Fermi arcs of all Weyl points are clearly visible on the projected Fermi surfaces. Our findings suggest that VAs is a fully spin-polarized Weyl semimetal with many-body correlated effects in the effective U values range from 1.5 to 2.5 eV.

Structural, electronic, magnetic, and thermoelectric properties of half Heusler alloys ZrCo1-XFeXSb (X = 0, 0.25, 0.5, 0.75, 1): A DFT study

The structural, electronic, magnetic, and thermoelectric properties of half-Heusler alloys ZrCo1-XFeXSb (X = 0, 0.25, 0.5, 0.75, 1) are investigated using the density functional theory. It is evident that ZrCoSbis a non-magnetic semiconductor. This study investigates the influence of substituting Fe for Co on the electronic structure and magnetic characteristics of ZrCoSb. The alloys transform into half-metallic ferromagnets as Fe substitutes Co. The indirect band gap of the ZrCo1-XFeXSb alloys decreases with increasing Fe content. The phonon dispersion curve is studied to determine the structural stability. The calculated values for the elastic constant for each composition satisfy the criteria for mechanical stability. To analyse its thermoelectric properties, the semi-classical Boltzmann transport theory is used to determine the Seebeck coefficients, electrical and thermal conductivities, and power factor as a function of temperature.

First-principles calculations on the mechanical, electronic, magnetic and optical properties of two-dimensional Janus Cr2TeX (X= P, As, Sb) monolayers

Janus materials possess extraordinary physical, chemical, and mechanical properties caused by symmetry breaking. Here, the mechanic properties, electronic structure, magnetic properties, and optical properties of Janus Cr2TeX (X= P, As, Sb) monolayers are systematically investigated by the density functional theory. Janus Cr2TeP, Cr2TeAs, and Cr2TeSb are intrinsic ferromagnetic (FM) half-metals with wide band gaps between spin-down channel and half-metallic gaps. The Curie temperature (Tc) of these monolayers are about 583, 608, and 597 K, respectively by Monte Carlo simulations based on the Heisenberg model. Additionally, it has been found that Cr2TeX (X= P, As, Sb) monolayers still exhibit FM half-metallic properties under biaxial strain ranging from −6% to 6%. At last, the Cr2TeP monolayer has a higher absorption coefficient than the Cr2TeAs and Cr2TeSb monolayers in the visible region. The results predict that Janus Cr2TeX (X= P, As, Sb) monolayers with novel properties have good potential for applications in future nanodevices.

Optimizing the thermoelectric behavior of novel quaternary CoIrMnX (X=Sn, Sb) alloys through chemical potential or carrier concentration doping

Materials exhibiting significant polarisation at high spin rates are considered the most promising candidates for spintronic devices. This study investigates the mechanical, optical, spin-polarised electronic structure, magnetism, and thermoelectric properties of CoIrMnX (where X = Sn, Sb). We performed calculations of quaternary Heusler alloys using first-principles calculations. The CoIrMnSn and CoIrMnSb compounds have the most stable Type III crystal structures, according to the calculations performed on the alloys under investigation. We found that the two alloys, CoIrMnSn and CoIrMnSb, possessed a half-metallic ferromagnetic structure, characterised by indirect band gaps of 1.008 eV and 0.806 eV in the predominant spin channels, respectively. Both alloys demonstrate a significant overall magnetic moment of 5 and 6 μβ, respectively. CoIrMnX (where X = Sn, Sb) are ferromagnetic half-metals with 100 percent spin polarisation, according to the results. The results of the elastic constants demonstrate the alloys' mechanical stability. We also investigated optical characteristics such as dielectric function, absorption, reflectance, and optical conductivity. CoIrMnX (where X = Sn and Sb) acts as an efficient absorber in the ultraviolet region and possesses a high refractive index. Alloys exhibit considerable potential as viable candidates for implementation in spintronic devices. The maximum ZT value for CoIrMnSn (CoIrMnSb) is 0.915 (0.6619). To achieve this value, it is necessary to either reduce the charge carrier concentration to n = 0.0812 x 1020 (0.0952 x 1020) cm-3 or the μ to 0.83843 (0.83806) Ryd. Substantially examined materials demonstrate considerable potential for application in the field of thermoelectrics.

Above room-temperature two-dimensional ferromagnetic half-metals in Mn-based Janus magnets

Two-dimensional (2D) ferromagnets and their heterostructures offer fertile grounds for designing fascinating functionalities in ultra-thin spintronic devices. Here, by first-principles calculations, we report the discovery of energetically and thermodynamically stable 2D ferromagnets with very strong in-plane magnetic anisotropy in MnXY (X = S and Se; Y = Cl, Br, and I) monolayers. Remarkably, we find that the Curie temperatures of the ferromagnetic MnSBr, MnSI, MnSeCl, and MnSeI monolayers are as high as 271, 273, 231, and 418 K, respectively. In addition, we demonstrate that these ferromagnetic monolayers are intrinsic half-metals with large spin bandgaps ranging from 2.5 to 3.2 eV. When spin–orbit coupling is considered in these ferromagnetic monolayers, the nature of their half-metal is almost unaffected. Finally, the strong in-plane magnetic anisotropy of MnSY (Y = Br, I) and MnSeY (Y = Cl, I) monolayers originate mainly from halogen and chalcogen atoms, respectively. Our work shows that 2D Janus Mn-based ferromagnetic half-metals may have appealing functionalities in high-performance spintronic applications.

The electronic structures, half-metallic ferromagnetism, optical, and thermoelectric responses of the Co-doped Au2S chalcogenide compound

The structural, electronic, magnetic, optical, and thermoelectric properties of diluted magnetic semiconductors (DMS) based on the chalcogenide compounds Au3CoS2, Au2Co2S2, and AuCo3S2 have been investigated using all-electron first-principles calculations. We have used the GGA-PBEsol and the around mean-field (AMF) correction scheme (GGA-PBEsol + U) for the exchange-correlation energies. Firstly, we calculated the equilibrium ground state of properties. Afterward, we evaluated the magneto-electronic properties using the GGA-PBEsol and GGA-PBEsol + U approaches. The computed spin-polarized band structures and density of states revealed the half-metallic ferromagnetic behavior for the studied compounds from both approaches. The half-metallicity is mainly due to the p-d hybridization of S and Co atoms. We also estimated the Curie temperatures using the mean-field approximation, and the results exceeded the ambient temperature. The real and imaginary components of the dielectric function, as well as the refractive index and reflectivity, were calculated up to 13.0 eV for both spin directions to explore the optical responses of AuCo3S2, Au2Co2S2, and Au3CoS2 compounds. The thermoelectric responses have also been reported for the spin-up orientation using the semi-classical Boltzmann transport theory and indicate that the half-metallic behavior is maintained at high temperatures. Finally, both the importance and potential applications of the studied compounds are discussed in this study.

High Curie temperature Heusler alloys RhMnCrZ (Z = Si, Ge) investigated by DFT and Monte Carlo methods

We utilize density functional theory (DFT) to conduct a comprehensive theoretical investigation of the quaternary RhMnCrZ (Z = Si, Ge) Heusler alloys. Our study focuse on analyzing the stability, electronic structure, magnetism, exchange interaction, and Curie temperature of these alloys. The stability of the alloys is verified by calculating and analyzing the formation energy, phonon spectrum, elastic constants, and melting temperature. The calculation results show that the alloys are natural half-metallic ferromagnets with lattice constants of 5.868 Å for RhMnCrSi and 5.980 Å for RhMnCrGe. Meanwhile, the effects of compression and expansion stress on the half-metallic property are simulated from a practical perspective. The magnetic calculation of the alloys shows an integer magnetic moment and adheres to the Slater-Pauling rule, which states that Mt=Zt-24. Based on crystal field theory, orbital hybridization theory, exchange interaction, etc., the coupling effect of electrons and the principle of integer magnetic moments are analyzed. The Heisenberg model is used to calculate the exchange interactions between all atoms. Various exchange interactions between atoms are analyzed, and it is concluded that the dominant mechanism is the ferrimagnetic ordered phase. What’s more, we calculate the Curie temperature of the RhMnCrZ (Z = Si, Ge) alloys, taking into account the exchange interactions. The Curie temperatures of both Heusler alloys are above 900 K, which is significantly higher than room temperature. RhMnCrZ (Z = Si, Ge) alloys show promise for spintronics applications, as indicated by theoretical simulation calculations.

Half-Metallic Ferromagnetism in TM-Doped GaN Nanosheet — A Potential Candidate for Spintronics Device Application

Density functional theory (DFT) analyses were carried out to study electronic structures and magnetic properties of Mn- and Cu-doped GaNNS. To investigate the influence of transition metal atoms (TM) on magnetic properties, we substituted Ga atoms with Mn and Cu atoms in different concentrations. Investigation shows that TM leads to electronic structural reconstruction which changes their properties in this way, and plays a significant role in spin polarization. Although the pure nanosheet is a nonmagnetic semiconductor, the doped atoms induce magnetism in the structure. The band gap changes monotonically depending on the concentration of TM atoms. The observed good half-metal ferromagnetism GaNNS:Mn, allows them to be a potential candidate for use in spintronics. The local magnetic moment calculated from Mulliken analyses for the Mn atom is approximately 4.05[Formula: see text][Formula: see text]B.

Long-range superconducting proximity effect in YBa2Cu3O7/La0.7Ca0.3MnO3 weak-link arrays

The interplay between ferromagnetism and superconductivity has attracted substantial interest due to its potential for exotic quantum phenomena and advanced electronic devices. Although ferromagnetism and superconductivity are antagonistic phenomena, ferromagnets (F) can host spin-triplet superconductivity induced via proximity with superconductors (S). To date, most of the experimental effort has been focused on single S/F/S junctions. Here, we have found the fingerprints of long-range superconducting proximity effect in micrometric weak-link arrays, formed by embedding YBa2Cu3O7 superconducting islands in a half-metallic ferromagnet La0.7Ca0.3MnO3 film. These arrays show magnetoresistance oscillations that appear at temperatures below the critical temperature of YBa2Cu3O7 for currents below a threshold, indicating their superconducting origin. This realization paves the way for device architectures displaying macroscopic quantum interference effects, which are of interest for field sensing applications, among others.

Electronic, magnetic, elastic and optical properties of Ba2CoTaO6 double perovskite oxide: A DFT study

In this study, the computational functionals GGA and mBj of density functional theory (DFT) were employed to explore the electronic structure of tantalum based double perovskite oxide Ba2CoTaO6. Computed tolerance (t) and octahedral (µ) factors deduce the cubic stability of the perovskite crystal. Negative formation energy indicates that the system is thermodynamically stable. The elastic constants satisfy the conditions for cubic stability and the Pagh’s index (B/G) evinces the brittle nature. The band structure and total density of states reveal the half-metallic nature with a 4.7 eV insulator indirect energy band gap at the Fermi level in the spin up direction. An integer-valued (4µB) magnetic moment is observed to favor the half-metallic ferromagnetism in the double perovskite oxide Ba2CoTaO6. Optical properties play a significant role in the design and functionality of optical devices and systems. In this aspect, the two parts of the dielectric function (real and imaginary) and the related parameters have been explored. The observed properties provide insights into possible applications of this system in spintronics and optoelectronics.

Study of magnetic, thermoelectric, and mechanical properties of double perovskites Be2XH6 (X = Cr and Mn) for spintronic and hydrogen-storage applications

Metal hydrides are highly significant for hydrogen storage because of high gravimetric and kinetic factors. Therefore, the double perovskites hydrides Be2XH6 (X = Cr and Mn) have outstanding hydrogen storage capability with gravimetric hydrogen densities of 7.9 wt% and 7.6 wt%, respectively. Moreover, the DFT-based PBE-GGA and TB-mBJ potential have been implemented to systematically analyze the electronic, Curie temperature, and magnetic characteristics of Be2XH6 (X = Cr and Mn). The tolerance factor and formation energy analysis indicate the structural and thermodynamic stabilities. The band structures, density of states and Curie Weiss law ensure the above room temperature half metallic ferromagnetism with complete spin polarization. The ultralow lattice thermal conductivity and high thermoelectric performance also significantly increase their importance. Finally, the mechanical and thermodynamic behavior have also been addressed in detail. These conclusions are significant for future hydrogen storage growth increases in metal hydrates.

Andreev Conductance in Disordered SF Junctions with Spin-Orbit Scattering

We calculate the conductance of a junction between a disordered superconductor and a very strong half-metallic ferromagnet admitting electrons with only one spin projection. A usual mechanism of Andreev reflection is strongly suppressed in this case since Cooper pairs are composed of electrons with opposite spins. However, this obstacle can be overcome if we take into account spin-orbit scattering inside the superconductor. Spin-orbit scattering induces a fluctuational (zero on average) spin-triplet component of the superconducting condensate, which is enough to establish Andreev transport into a strong ferromagnet. This remarkably simple mechanism is quite versatile and can explain long-range triplet proximity effect in a number of experimental setups. One particular application of the suggested effect is to measure the spin-orbit scattering time τSO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ au _{\ ext {SO}}$$\\end{document} in disordered superconducting materials. The value of Andreev conductance strongly depends on the parameter ΔτSO\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta \ au _\ ext {SO}$$\\end{document} and can be noticeable even in very disordered but relatively light metals like granular aluminum.

Exploring of Be1-xCrxSe alloys for spintronics and optoelectronic applications

In this study, spin polarized density functional theory (DFT) is implemented to predict physical characteristic of Be1-xCrxSe (x = 6.25%, 12.5%, 18.75%, 25%) compound. The electronic characteristics of pure BeSe compound show semiconductor behavior but after Cr doping BeSe elucidate half-metallic ferromagnetism (HMF) for all doping concentrations. The outcomes elucidate the total magnetic moment MTot per Cr-atom are 4.0028, 4.0027, 4.0021 and 4.0002 μB for 6.25%, 12.5%, 18.75%, 25% concentrations, respectively and the magnetism mainly originated from d-state of the impurity atom which is further ensured from the magnetic spin density. Furthermore, the optical parameters are also computed to determine the effect of doping on the material’s response to incident light of energy spanning from 0 to 10 eV. The optical study depict that the studied systems possess maximum absorbance and optical conductivity in UV-range with minimal reflection. The overall outcomes illustrate that the Cr doped beryllium selenide (BeSe) is promising material for spintronic and optoelectronic devices.

Exploring ZnFeSnO4 double spinel: A thorough investigation of mechanical, dynamical, magneto-electronic properties and lattice thermal conductivity

Double spinel materials ABB'O4 emerge as an innovative class of oxides with promising technological applications. First-principles calculations are employed to explore the fundamental properties of the double spinel ZnFeSnO4. Its elasticity and dynamic stability are investigated using the pseudo-potential plane wave (PP-PW) method, while the full-potential linearized augmented plane wave (FP-LAPW) approach is used to study its electronic and magnetic properties. The results reveal favorable thermodynamic stability, mechanical robustness, and dynamical stability for ZnFeSnO4. Analysis using GGA + U (U = 6 eV) in the FP-LAPW framework predicts half-metallic ferromagnetism, a highly desirable characteristic for spintronic applications due to its potential spin-polarized currents. However, the use of the mBJ functional results in semiconducting character with bandgaps of 1.813 eV, and 1.524 eV for spin-up and spin-down, respectively. Hence, the outcomes of the computations pertaining to the electronic characteristics are contingent upon the selection of the exchange-correlation functional. Furthermore, the calculated low lattice thermal conductivity of ZnFeSnO4 indicates its potential suitability for thermoelectric applications.

Ab initio prediction of half-metallic and metallic ferromagnetism in ZnO:(Co,Cr) systems

Doping effects on the electronic and magnetic properties of Zn1−x (Co,Cr) x O systems are investigated within Local Spin Density Approximation and Hubbard U methods. Based on Density Functional Theory the spin-polarization band structures, density of states for investigated systems are calculated. Systematic analysis of the electronic properties shows that TM-doped ZnO has generated new energy levels in the vicinity of Fermi energy level. From first-principle calculations we obtained Cr-ZnO and Co-ZnO systems are metallic and half-metallic ferromagnetic materials, respectively. The obtained results for Cr-doped ZnO 128- and 192-atom supercell systems show magnetic properties with higher Curie temperature than room temperature. There are large local moments, ∼2.9 and ∼4.2 for Co and Cr dopants, respectively. Magnetic moments are related with two electron defects in the supercell structure and unpaired electrons of transition metal. The ferromagnetic and antiferromagnetic phases and the total energy are obtained for x = 2.08%, 3.125%, 4.16%, 6.25%, 8.3%, 12.5%, and 25% impurity concentrations for doped ZnO.