Half-metallic Behavior Research Articles

Half-metallic and thermodynamic properties of new d 0 CsCaZ (Z= Ge, Sn and Pb) half Heusler alloys: A spin-based devices vision for the future

Density functional theory (DFT) was applied to investigate the structural, electronic, elastic, magnetic, thermodynamic and half-metallic properties of the newly d0 Heusler alloys (HAs) CsCaZ (Z= Ge, Sn and Pb). Spin-polarised calculations show that the compounds studied are half-metallic with a magnetic moment of 1.00 μB at the equilibrium lattice parameter, which obeys the well-known Slater–Pauling rule Mtot = 8 – Zt. The half-metallic behavior of the compounds CsCaGe, CsCaSn and CsCaPb is predicted with respect to the equilibrium lattice constants for CsCaGe, CsCaSn and CsCaPb with a narrow band gap in the majority spin channel. Furthermore, the elastic constants (Cij) showed that these materials are ductile and anisotropic. In addition, the negative values of the calculated formation energy and cohesion energy indicate that CsCaZ (Z= Ge, Sn and Pb) are likely to be experimentally synthesized. Non-equilibrium Gibbs function is employed to calculate the thermodynamic properties through the quasi-harmonic Debye model in which the bulk modulus, heat capacity, Debye temperature, thermal expansion coefficient, and entropy are investigated at 0-20 Gpa pressure and 0-1200 K temperature ranges. The significant half-metallic behavior makes the CsCaZ (Z= Ge, Sn and Pb) compounds strong candidates for spintronic applications.

Electronic, Thermodynamic Stability, and Band Alignment Behavior of the CoVSi/NaCl Heterojunction

We report the band discontinuity of the CoVSi/NaCl heterointerface. First principle calculations based on density functional theory using GGA, GGA + U, and GGA + mbJ approximations were applied to study the structural, electronic, and band alignment properties. Structural and thermodynamic stability studies indicate that this semiconductor - dielectric heterojunction can be synthesized experimentally in thermodynamic equilibrium conditions. The valence and conduction band offset values (VBO and CBO) were 0.74 and 3.02 eV, respectively. Also, the effective electron affinity parameter (χ e) for both CoVSi and NaCl were calculated as ∼1.51 and ∼0.769 eV, respectively, using Anderson’s law. The study of the electronic structure expresses the occurrence of half-metallic ferromagnetic behavior with a narrow band gap of about 0.09 eV. In this heterojunction, electrons and holes were confined to the CoVSi layers, and conduction band minimum and valence band minimum were replaced in the CoVSi layers. This restriction, applied to load carriers on one side of the interface, significantly increases the light-material interaction in light-emission programs. Therefore, this heterojunction can be recommended for light-emitting applications and thin atomic layer materials with quantum confinement of charge carriers.

Cr2Ge2Te6 nanoribbons with perpendicular magnetic anisotropy and half metallicity: a DFT study

Cr2Ge2Te6 is an intrinsic ferromagnetic material with a van der Waals layered structure and it shows promise in spintronics applications. In this work, we investigated the edge effects in Cr2Ge2Te6 nanoribbons and the change in magnetic properties considering spin-orbit effects. Edge formation energies evidenced stability in nanoribbons with TeCr edges. Stability remains in these nanoribbons in presence of Te vacancies at the edge. New bonds appear in the nanoribbons due to edge effects and induce half-metal (HM) behavior. The metallic part is dominated by Te-p, Ge-p, and Cr-d orbitals. Both stable nanoribbons present perpendicular magnetic anisotropy. Our results point Cr2Ge2Te6 nanoribbons as key for the construction of spintronic devices since HM materials with perpendicular magnetic anisotropy produce 100% spin-polarized out-of-plane current.

Theoretical prediction of doping iron ions effect on the optoelectronic and magnetic cobalt-based perovskite (Co1-xFexScO3)

The ab-initio framework has taken place by means of the Full-potential Linear Augmented Plane-Wave (FP-LAPW) method, using the modified Becke-Johnson exchange potential approximation. This modified method was carried out to study the effects of doping iron ions on the structural, electronic, magnetic, and optical properties of CoScO3 perovskite compound. Doping Fe ions have formed a nonstoichiometric perovskite Co1-xFexScO3 where x = 0, 0.25, 0.50, 0.75, and 1. all doped compounds crystallized in a tetragonal lattice due to the Jahn-Teller effect, while the lattice constant was calculated and found to vary between the value of the two pure compounds. Meanwhile, the stabilities of the studied compounds are shown in the negative values of the formation energy. The magnetic moment was calculated and the whole compounds showed a ferromagnetic behavior. Co1-xFexScO3 perovskite is a potential candidate for spintronic application due to the presence of the half metallic behavior. All optical spectrums including dielectric function, absorption coefficient, reflectivity and refractivity index, and energy loss function show remarkable features for the proposed perovskites.

Itinerant magnetism, electronic properties and half-metallicity of Co2ZrSn and Co2HfSn Heusler alloys

Half-metallic ferromagnetic alloys are attracting considerable interest for their potential applications in spintronic devices. Co-based Heusler alloys are considered to be promising half-metallic compounds as they combine suitable magnetic, electronic and transport properties with compositional versatility and high thermal stability. In this work, Co 2 ZrSn and Co 2 HfSn Heusler alloys were studied by combining experimental and ab-initio investigations in order to accurately estimate their electronic density of states in proximity of the Fermi level and to determine their magnetic and electronic properties. Magnetization measurements, performed between 2 K and 550 K, suggest for both alloys a gradual transition from localized ferromagnetism to weak itinerant ferromagnetism with increasing temperature, well described by a simple mean field model up to the Curie temperature (454 K in Co 2 ZrSn and 432 K in Co 2 HfSn) and beyond. Ab-initio calculations were performed using two exchange-correlational functionals, PBE and PBE optimized for solids (PBEsol), in order to assess the reproducibility of theoretical results. Overall, band structures and density of states (DOS) diagrams indicated, for both compounds, the presence of a half-metallic band gap in the minority spin sub-band. The dependence of magnetic moments and band gap width on cell parameters is discussed in detail. Calculated magnetic moments and cell parameters satisfactorily match the experimental results obtained in this work and previously reported in the literature. • Itinerant weak ferromagnetic behaviour is confirmed for both alloys as they follow the Edwards-Wohlfarth model. • The mean field model indicates that the density of states profiles at the Fermi level are smooth. • Ab-initio calculation performed with PBE and PBEsol functionals show half-metallic behaviour at 0 K. • A crossover from localized magnetism to itinerant magnetism as function of temperature was found for both alloys. • The M/T crossover can be attributed to a change in spin-flip mechanism at low temperature.

Investigation of the physical properties of CoRuVAl equiatomic quaternary Heusler alloy using first-principles calculations

We have computed the structural, mechanical, and thermal stability, as well as electronic, magnetic, and transport properties of the CoRuVAl equiatomic quaternary Heusler alloy. The electronic structure of the CoRuVAl alloy shows an indirect band gap of 0.279 eV at Fermi level in the spin down channel and metallic overlap in the spin up channel, indicating the presence of half-metallic behavior. This alloy exhibits a robust half-metallicity during lattice deformation. The effect of changing Hubbard values on the electronic structure was also investigated. We have studied the inclusion of spin orbit coupling (GGA + SOC) in the electronic structure due to the presence of heavier atoms, including Ru. We have calculated spin-dependent transport coefficients, including Seebeck coefficient, thermal conductivity, and electrical conductivity for both spin configurations by varying the temperature, and this alloy could be used in the future in both spintronic and thermoelectric devices.

First principles investigations of optoelectronic and magnetic properties of co-doped zinc sulphide by 3d and 4f elements

In this work, optoelectronic and magnetic properties of Co-doped and (Co, Sm) co-doped ZnS have been studied using the first principles calculation based on density functional theory (DFT) and FP-LAPW method with GGA and GGA + U approximations in zinc blende structure. The lattice parameter will increase by (Co, Sm) co-doping ZnS. The difference in total energy is calculated and confirms the stability of ZnS: Co in ferromagnetic states (FM) and ZnS: (Co, Sm) in antiferromagnetic states (AFM). The total magnetic moment is found to be more interesting by (Co, Sm) co-doping. The band structure, the total density of states (TDOS) and partial density of states (PDOS) show that ZnS: Co has a semiconducting character. While ZnS: (Co, Sm) has half-metallic character behavior with 100% spin polarization at the Fermi level provided by the RE-4f states. Moreover, optical properties such as dielectric functions and absorption coefficients for ZnS: Co and ZnS: (Co, Sm) were also discussed and found to be more interesting in the visible region by (Co, Sm) co-doping. The improved optical and magnetic results indicate that (Co, Sm) co-doped ZnS can be used as a promising candidate for optoelectronic and spintronic devices in the future.

Effects of Mono-Vacancies and Co-Vacancies of Nitrogen and Boron on the Energetics and Electronic Properties of Heterobilayer h-BN/graphene.

A study is carried out which investigates the effects of the mono-vacancies of boron (VB) and nitrogen (VN) and the co-vacancies of nitrogen (N), and boron (B) on the energetics and the structural, electronic, and magnetic properties of an h-BN/graphene heterobilayer using first-principles calculations within the framework of the density functional theory (DFT). The heterobilayer is modelled using the periodic slab scheme. In the present case, a 4 × 4-(h-BN) monolayer is coupled to a 4 × 4-graphene monolayer, with a mismatch of 1.40%. In this coupling, the surface of interest is the 4 × 4-(h-BN) monolayer; the 4 × 4-graphene only represents the substrate that supports the 4 × 4-(h-BN) monolayer. From the calculations of the energy of formation of the 4 × 4-(h-BN)/4 × 4-graphene heterobilayer, with and without defects, it is established that, in both cases, the heterobilayers are energetically stable, from which it is inferred that these heterobilayers can be grown in the experiment. The formation of a mono-vacancy of boron (1 VB), a mono-vacancy of nitrogen (1 VN), and co-vacancies of boron and nitrogen (VBN) induce, on the structural level: (a) for 1 VB, a contraction n of the B-N bond lengths of ~2.46% and a slight change in the interfacial distance D (~0.096%) with respect to the heterobilayer free of defects (FD) are observed; (b) for 1 VN, a slight contraction of the B-N of bond lengths of ~0.67% and an approach between the h-BN monolayer and the graphene of ~3.83% with respect to the FD heterobilayer are observed; (c) for VBN, it can be seen that the N-N and B-B bond lengths (in the 1 VB and 1 VN regions, respectively) undergo an increase of ~2.00% and a decrease of ~3.83%, respectively. The calculations of the Löwdin charge for the FD heterobilayer and for those with defects (1 VB, 1 VN, and VBN) show that the inclusion of this type of defect induces significant changes in the Löwdin charge redistribution of the neighboring atoms of VB and VN, causing chemically active regions that could favor the interaction of the heterobilayer with external atoms and/or molecules. On the basis of an analysis of the densities of states and the band structures, it is established that the heterobilayer with 1 VB and VBN take on a half-metallic and magnetic behavior. Due to all of these properties, the FD heterobilayer and those with 1 VB, 1 VN, and VBN are candidates for possible adsorbent materials and possible materials that could be used for different spintronic applications.

Effect of 5d state-based full-Heusler alloys on the structural, electronic and magnetic properties of new half metallic ferromagnetism

First-principles calculations of structural, elastic, electronic and magnetic properties of full-Heusler Ir2HfB, Ir2HfAl and Ir2HfGa have been realized by full-potential linearized augmented plane wave (FP-LAPW) method implemented inWIEN2K code. The Perdew–Burke–Ernzerh of generalized gradient approximation (PBE-GGA) carried out the computation of different parameters to describe elastic and structural properties. The calculation of structural properties revealed that the three alloys are stable in cubic AlCu2Mn-type structure in ferromagnetic state. The elastic constants calculation shows the three alloys satisfy the stability criteria. Indeed, the calculated spin-polarized electronic band structure and density of states using generalized gradient approximation (GGA) show that Ir2HfZ (Z = B, Al, Ga) alloys have a metallic character. The influence of strong electronic correlation has been considered in GGA+Uand mBJ-GGA+U approximations that allows for improving the width of the band gap. The calculations carried out with GGA+U and mBJ-GGA+U show that Ir2HfAl and Ir2HfGa have a half-metallic behavior; however, Ir2HfB has a near half-metallic character. The calculated magnetic moments of Ir2HfB, Ir2HfAl and Ir2HfGa in a regular cubic structure with GGA+U and mBJ-GGA+U equal 1μB. With mBJ-GGA+U, the spin polarization values are 100% for Ir2HfAl, Ir2HfGa and 99.90% for Ir2HfBto be applicable for spintronics.

Investigation on magnetic properties of W-doped diamond via first-principles

The electronic and magnetic properties of W-doped diamond were investigated by first-principles calculation. The results revealed that the substitutional site was more favorable than interstitial site for W atom in diamond. The W-doped diamond exhibited the half metallic behavior and stable ferromagnetism with a magnetic moment of 2 μB, while the intrinsic diamond was non-magnetic. The density of states implied that magnetism originated from the p-d hybridization between the W-5d and C-2p states. The spin charge density and magnetic moment of W-doped diamond stemmed from the W atom and the surrounding C atoms. Therefore, the W-doped diamond would be a promising novel type of dilute magnetic semiconductor and could possess a great potential application in spintronic and micro-electromechanical system devices.

Consequences of Tuning Rare-Earth RE3+-Site and Exchange-Correlation Energy U on the Optoelectronic, Mechanical, and Thermoelectronic Properties of Cubic Manganite Perovskites REMnO3 for Spintronics and Optoelectronics Applications.

Both rare-earth SmMnO3 and EuMnO3 compounds that belong to transition-metal-based manganite perovskites REMnO3 have been studied deeply in this paper. The structural, elastic, optoelectronic, magnetic, mechanical, and thermoelectronic properties of cubic SmMnO3 and EuMnO3 compounds have been computed using the full-potential linearized augmented plane-wave (FP-APLW) method in the frame of density functional theory (DFT). To compute the ground-state energy, the effect of exchange–correlation potential was treated via the application of generalized gradient approximation within Perdew, Burke, and Ernzerhof (PBE-GGA) plus its corrected method (GGA + U). The spin-polarized results of band structures, density of states (DOS), and magnetic moments show that SmMnO3 and EuMnO3 have ferromagnetic half-metallic (FM-HM) behavior. Optical responses of dielectric function (ε(ω)) are explained by computing the real ε1(ω) and imaginary ε2(ω) parts of ε(ω), refractive index n(ω), extinction coefficient k(ω), absorption coefficient α(ω), optical conductivity σ(ω), reflectivity R(ω), and energy loss function L(ω) using GGA and GGA + U. Also, we computed and discussed the thermoelectronic properties of SmMnO3 and EuMnO3, including Seebeck coefficient (S), holes and electrons charge carrier concentration (n), electrical conductivity (σ/τ), power factor (S2σ/τ), figure of merit (ZT), thermal conductivity (κ), and specific heat capacity (CV), as a function of temperature (T), using GGA and GGA + U methods based on BoltzTrap scheme. The present results confirm the perfect mechanical and thermal stability of two perovskites which make SmMnO3 and EuMnO3 promising materials for spintronics, optoelectronics, high-temperature, and other related applications.

Room-temperature half-metallicity in rich Ti-alloyed [formula omitted] monolayer

A new family of MoSi2N4-type monolayers have been extensively studied since it was recently synthesized, but half-metallic behavior is observed infrequently and unstable in the new family. Here, based on antiferromagnetic semiconductor CrSi2N4 monolayer, we predict a ferromagnetic half-metallicity (FHM) in alloy compound TiCrSi4N8 monolayer with a minority-spin gap of 3eV and a considerable magnetic anisotropy energy by applying first-principles calculations. The FHM of TiCrSi4N8 are robust against biaxial strain from −3% to 3%. The TiCrSi4N8 belongs to XY ferromagnet with negligible in-plane magnetocrystalline anisotropy and the Curie temperature is estimated to be near room temperature by Monte Carlo simulation with the consideration of symmetric and antisymmetric exchange interactions. Such a FHM at room temperature may be permitted in the range of Ti concentrations from 0.5 to 0.75. Strong d−−d hybridization between Cr and Ti atoms and the larger exchange splitting of Cr-d orbitals with respect to Ti-d orbitals are origin of the HM and magnetic moment of Cr atom, and ferromagnetic coupling between Cr atoms is due to the Cr–N–Cr superexchange interaction. Besides, the applied potentials of TiCrSi4N8 are further expanded by the large Young’s modulus and strong bending resistance. Thus, the rich Ti-alloyed CrSi2N4 monolayers are noteworthy candidates for generating spin current source.

Energy band reconstruction mechanism of Cl-doped Cu2O and photocatalytic degradation pathway for levofloxacin

Cl-doped Cu 2 O microparticles were prepared by hydrothermal synthesis . XRD, BET, SEM, TEM, UV–Vis and RSM were used to reveal the microstructure, optical properties and degradation regularity of the Cl-doped Cu 2 O microparticles. The band gap structures and state densities of Cl-doped Cu 2 O microparticles were computed based on density functional theory . The major intermediate degradation products and potential photocatalytic degradation pathways of levofloxacin were identified by HPLC–MS/MS. The photocatalytic active sites of levofloxacin and its intermediate products were calculated based on the frontier electron densities. The results showed that the prepared Cl-doped Cu 2 O microparticles increased the specific surface area and absorption efficiency of visible light compared with undoped pure Cu 2 O. The doping of Cl introduced hybrid orbitals and oxygen vacancy defects in the Cu 2 O crystal cell and decreased the forbidden bandwidth of Cu 2 O crystal microparticles, leading to a redshift of the absorption edge . Cl doping could form a shallow donor impurity energy level composed of Cl 3 p orbital in the energy gap of Cu 2 O and make the energy band denser and move to a lower energy, which could promote the electron leap to the conduction band through the impurity level . The doping of Cl can make the density of states curve of the Cu 2 O crystal shift to low-energy and the Cl-doped Cu 2 O rendered to half-metallic behavior and characteristic behavior of an n type semiconductor. The photocatalytic degradation of levofloxacin was attributed to attack of photogenerated holes and hydroxyl radicals , and the ring opening of the piperazine ring by oxidation and decarboxylation reactions from the quinolone ring might be two photocatalytic degradation pathways. This study revealed the mechanism of oxygen vacancy formation and the change rules of the band structure by doping of the nonmetal chlorine into Cu 2 O crystallites . • Migration laws of band structure and state density of Cl-doped Cu 2 O were revealed. • Doping of Cl introduced hybrid orbitals and oxygen vacancies in the Cu 2 O crystal. • Doping of Cl decreased band gap of Cu 2 O and led to red shift of absorption edge. • Holes and hydroxyl radicals are the main photocatalytic active species. • Degradation paths of levofloxacin were piperazine ring opening and decarboxylation.

First-principles predictions of tunable half metallicity in zigzag GaN nanoribbons with possible applications in CO detection and spintronics

Based on systematic first-principles density-functional theory simulations, we predict that the zigzag GaN nanoribbons (ZGaNNRs) can be used both as highly efficient CO detectors as well as spin filters. Our calculations, performed both on infinitely long nanoribbons, and also on finite strands, suggest that: (a) CO binds strongly at the edges of ZGaNNRs, and (b) that several of the resultant configurations exhibit half-metallic behavior. We considered various edge-passivation sites and found that all the resultant structures are thermodynamically stable. The metallic, half-metallic, and semiconducting configurations are observed as a function of CO passivation coverage. We also compute the current–voltage (I–V) characteristics of various structures using the Landauer formalism, and find that the devices made up of half-metallic configurations act as highly-efficient spin filters. The effect of CO concentration is also investigated which suggests a viable way to not just tune the electronic band gap of ZGaNNRs, but also their half metallicity. Our simulations thus suggest a new direction of research for possible device applications of III–V heterostructures.

First-principles calculations to investigate new ferromagnetic quaternary Heusler alloys FeZrTiZ(Z=Si, Sn, Pb): Compatible for spin polarized device and waste heat recovery applications

In this article, we have studied the structural, electronic, magnetic, mechanical and thermoelectric properties of new quaternary Heusler alloys FeZrTiZ (Z = Si, Sn, Pb), using ab-initio simulation methods. Our structural phase stability studies show that all these compounds stabilize in Y1-type structure and showing ferromagnetic ground state. From the calculation based on Generalized Gradient Approximation method we found that all these alloys are having half metallic behavior with the band gap value of around 1eV in one of the spin channels. The half metallic nature of these alloys is a precursor for high spin polarization. These alloys also satisfy the Slater-Pauling rule with magnetic moment of MT = NV − 18 for half metallicity and as a result they have a total magnetic moment of 2μB. The calculated elastic constants convey the mechanical stability of these alloys and though they have a cubic structure they exhibit strong mechanical anisotropy with ductile behavior. The Seebeck coefficient and the thermoelectric figure of merit were calculated using semi-classical Boltzmann transport theory. The highest Seebeck coefficient value for FeZrTiZ (Z = Si, Sn, Pb) is 110.5 μV/K, 121.8 μV/K and 100.6 μV/K respectively at the temperature 900 K, 600 K and 750 K and the corresponding figure of merit is 0.85, 0.9 and 0.59. The observation of half metallicity indicates that these materials can be used in spintronic devices and the observation of substantial thermoelectric figure of merit suggests that these materials can be used in waste heat recovery.

Spin and orbital transport in rare-earth dichalcogenides: The case of EuS2

We perform first-principles calculations to determine the electronic, magnetic, and transport properties of rare-earth dichalcogenides, taking a monolayer of $H$-phase ${\mathrm{EuS}}_{2}$ as a representative. We predict that the $H$ phase of the ${\mathrm{EuS}}_{2}$ monolayer exhibits a half-metallic behavior upon doping with a very high magnetic moment. We find that the electronic structure of ${\mathrm{EuS}}_{2}$ is very sensitive to the value of Coulomb repulsion $U$, which effectively controls the degree of hybridization between Eu $f$ and S $p$ states. We further predict that the nontrivial electronic structure of ${\mathrm{EuS}}_{2}$ directly results in a pronounced anomalous Hall effect with nontrivial band topology. Moreover, while we find that the spin Hall effect closely follows the anomalous Hall effect in the system, the orbital complexity of the system results in a very large orbital Hall effect, whose properties depend very sensitively on the strength of correlations. Our findings thus promote rare-earth-based dichalcogenides as a promising platform for topological spintronics and orbitronics.

Ab-initio and Monte Carlo Simulations of the New Half-Heusler Alloy NiCrGa

Abstract: In this work, we are investigating the electronic and magnetic properties of the new NiCrGa half-Heusler alloy (HHA), by using the ab-initio and Monte Carlo simulations (MCSs). The ab-initio method is performed under the pseudo-potential method and the generalized gradient approximation GGA. The density of states (DOS) and the band structure calculations show that the alloy NiCrGa reveals a nearly half-metallic (HM) behavior. In particular, the Slater-Pauling (SP) rule has been confirmed when using the magnetic moments of the individual constituents of the NiCrGa compound. The Monte Carlo simulations (MCSs) are accomplished using the Metropolis algorithm. In order to determine the transition temperature, we are based on the behavior of the total magnetization and susceptibility of this material. We also presented and discussed the hysteresis loops of the half-Heusler compound, for fixed values of temperature, exchange coupling interactions and crystal field. It is found that when increasing the crystal field, the surface of the loops increases and vice versa. Keywords: Half-Heusler alloy, NiCrGa, Slater pauling, DFT method, Monte Carlo study.

3d-Electron-doping induced multiferroicity and half-metallicity in PbTiO3

Atomic interactions can be used to control and tune the physical properties of the systems, which are different from the pristine structure. Herein, we explored the ferroelectric, magnetic, and electronic properties of 3d transition metals (TM = Sc, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn)-doped PbTiO3 utilizing density functional theory calculations. The structural stability of the undoped and doped systems is checked by computing the formation enthalpies in terms of the Convex Hull analysis, affirms the experimental realization of all the motifs. It is established that the versatile multiferroic properties can be obtained by TM-doping, which are ranging from non-magnetic/magnetic semiconductor or conductor (Sc-, Zn-, and Ni-doped systems)/(V-, Mn-, Fe-, and Cu-doped systems) to half-metallic ferromagnetic (Cr- and Co-doped systems). The most striking feature of the present study is that Cr- and Co-doped systems display half-metallic behavior along with a moderate spontaneous polarization (SP) of 40.07 and 59.77 μC/cm−2, respectively. The metallicity in the spin-minority channel mainly comes from the Cr and Co 3dyz+xz orbitals with a small contribution from d xy . However, Zn-doped motif displays a higher SP magnitude of 70.32 μC/cm−2 than that of other doped systems. Finally, the induced magnetism in these doped structures is explained by addressing the low and high spin state configurations of TM ions. As it found that Mn- and Fe-doped structures exhibit a larger moment of 2.9 and 2.7 μ B and lie in a high spin states of S = 2.0 and 2.02, respectively. Hence, our calculations highly demand the experimental verification of these doped materials for their potential realization in spintronic devices.

Structural properties, electronic band structure, magnetic and mechanical characteristic of XFeGe (X = Co, Cr, Ni) half Heusler compounds: Insights from DFT calculation

The structural, electronic, magnetic and thermodynamic properties of XFeGe (X = Co, Cr, Ni) half Heusler compounds are studied using first-principles calculation within density functional theory in five different atomic configurations. For each configuration, their optimized lattice constants are determined. It showed that the configuration of type 3 is energetically the most stable. From the spin-polarized band structure and density of states, it is found that CoFeGe alloy exhibits a half-metallic character with integer magnetic moments of 3.00μBper formula unit at their equilibrium volume, whereas NiFeGe and CrFeGe exhibit a metallic character. These results indicate that the magnetic moment mainly originates from the Fe atoms. The calculated equilibrium volume for the three compounds CoFeGe, CrFeGe, and NiFeGe at various temperatures is predicted. The heat capacity at constant volumeCVhas been calculated as a function of temperature and pressure. Additionally, the calculated elastic constants for the three compounds confirm the mechanical stability criteria for cubic systems.

Bipolar magnetic semiconductors and half-metals in transition metals doped SnSe2 zigzag nanoribbons

The magnetic and electronic properties of transition metals (TM) (TM = Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) doped SnSe2 zigzag nanoribbons (ZNRs) are investigated by employing density functional theory. When an Sn atom on edge of ZNR is substituted by Sc atom, the ZNR behaves as bipolar magnetic semiconductors with 100% spin polarization of valence band and conduction band carriers, where the spin-polarization direction can easily be switched by an external electric field. The Cr-doped ZNR is a spin-gapless semiconductor in which the valence band and conduction band in the spin-up channel touch each other at Fermi energy. The others either are usual magnetic semiconductors or nonmagnetic semiconductors. When two Sn atoms on the edge are substituted by Cr atoms, it is observed that the SnSe2 nanoribbon exhibits half-metallic behavior. Either one Cr dopant or two Cr dopants on edge, the nanoribbons have stable 100% spin polarization of conduction carriers at a wide energy range. These findings demonstrate that the Sc-, Cr-, and 2Cr-doped SnSe2 zigzag nanoribbons are excellent candidates for spintronics.