Half-metallic Character Research Articles

B2-disorder effects on the structural, electronic and magnetic properties of Co2MnAl Heusler alloy

Co-based Heusler alloys are mostly studied for their half metallicity, resulting in 100% spin polarization and a very high Curie temperature, which are the prerequisites for spintronics devices. As the site (swap) disorder has a significant impact on these properties, understanding of the impact of site disorder on these properties is of great interest for the spintronic community. First principle calculations within density functional theory (DFT) have been carried out on the structural, electronic, and magnetic properties of the B2 disordered Co2MnAl full Heusler alloy along with that of L21 ordered structure for comparison purpose. The plane wave pseudopotential method, within the Generalized Gradient approximation for exchange correlation functional was used to study B2 disordered Co2MnAl Heusler alloy. The degree of site (swap) disorder is systematically varied from 0% to 100% in steps of 12.5% using the supercell approach. DFT calculations reveal no considerable changes in the structural and magnetic properties of Co2MnAl by the presence of the disorder and are found to be the same as for the L21 structure. However, on the other hand, electronic properties such as, the spin polarization increased from 76% to 100% in the case of B2-25% and B2-75% disorder from the L21 structure resulting in half-metallic character. The study further suggests that static-magnetization and structural properties of Co2MnAl Heusler alloy are robust against site disorder.

Electron-magnon scattering in an anisotropic half-metallic ferromagnetic Weyl semimetal Co3Sn2S2

${\mathrm{Co}}_{3}{\mathrm{Sn}}_{2}{\mathrm{S}}_{2}$ is a magnetic Weyl semimetal, anisotropic ferromagnet, and half-metal in a single material. These qualities modify the spin dynamics and behavior of electron-magnon scattering. We have investigated this unconventional ferromagnet for modified electron-magnon scattering behavior using temperature and magnetic field dependent resistivity. ${\mathrm{Co}}_{3}{\mathrm{Sn}}_{2}{\mathrm{S}}_{2}$ exhibits exponential suppression of spin-flip electron-magnon scattering below a characteristic crossover temperature which separates the regime of anomalous magnon scattering from one-magnon scattering. Interestingly, the Weyl fermion mediated spin dynamics with large magnetocrystalline anisotropy can also cause exponential suppression of electron-magnon scattering giving similar behavior in resistivity. The gap characterizing the suppression of electron-magnon scattering is 2.46(4) meV and increases linearly with magnetic field. The suppression of electron-magnon scattering could occur from half-metallic or anisotropic character but the presence of anomalous-magnon scattering at low temperatures evinces the half-metallic nature. A large anisotropy gap in magnon dispersion of half-metal can help prevent the deviation from 100% spin polarization at low temperatures.

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.

First-Principles Calculations of the Structural, Electronic, Optical, and Mechanical Properties of 21 Pyrophosphate Crystals

Pyrophosphate crystals have a wide array of applications in industrial and biomedical fields. However, fundamental understanding of their electronic structure, optical, and mechanical properties is still scattered and incomplete. In the present research, we report a comprehensive theoretical investigation of 21 pyrophosphates A2M (H2P2O7)2•2H2O with either triclinic or orthorhombic crystal structure. The molecule H2P2O7 is the dominant molecular unit, whereas A = (K, Rb, NH4, Tl), M = (Zn, Cu, Mg, Ni, Co, Mn), and H2O stand for the cation elements, transition metals, and the water molecules, respectively. The electronic structure, interatomic bonding, partial charge distribution, optical properties, and mechanical properties are investigated by first-principles calculations based on density functional theory (DFT). Most of these 21 crystals are theoretically investigated for the first time. The calculated results show a complex interplay between A, M, H2P2O7, and H2O, resulting in either metallic, half-metallic, or semi-conducting characteristics. The novel concept of total bond order density (TBOD) is used as a single quantum mechanical metric to characterize the internal cohesion of these crystals to correlate with the calculated properties, especially the mechanical properties. This work provides a large database for pyrophosphate crystals and a road map for potential applications of a wider variety of phosphates.

Half-metallic ferrimagnetic characteristics of novel Ti2-based ternary Heusler alloys: DFT calculations

Half-metallic ferrimagnetic characteristics of novel Ti2-based ternary Heusler alloys: DFT calculations

First-principal study of structural, elastic, electronic and magnetic properties for the ternary and quaternary Heusler Compounds (Co[formula omitted]Fe[formula omitted])[formula omitted]CrSn

In this paper, we performed calculations on structural, mechanical, electronic and magnetic properties of ternary and quaternary Heusler Compounds (CoxFe1−x)2CrSn, as well as on their possible half-metallic properties, using the GGA or GGA + U method based on first-principles calculations. We found these compounds are all in the Y1-structure phase, which is the most stable and that their ground states are either ferromagnetics or ferrimagnetics. At the equilibrium lattice constant, the electronic structures obtained by GGA or GGA + U methods indicate that three compounds (Fe2CrSn, CoFeCrSn and Co2CrSn)can exhibit typical or almost half-metal character. For CoFeCrSn compound the total magnetic moment per formula unit is 3.0 μB, which is in good agreement with the Slater–Pauling rule, and Cr atoms are the main source of total magnetic moment. All the aforementioned results indicate that at least one or more of these quaternary Heusler compounds would be an ideal candidate in spintronics. We investigated the Curie temperature TC of these compounds and found them higher than 429 K.

Investigation of half-metallic ferromagnetism and transport properties of pnictide oxides REZnAsO (RE=La, Ce, Nd, Pr, Gd, Eu, Sm, Dy) for spintronics

The electronic, half-metallic and thermoelectric characteristics of pnictide oxides REZnAsO (RE = La, Ce, Nd, Pr, Gd, Eu, Sm, Dy) have been examined using full-potential linearized augmented plane wave (FP-LAPW) technique. The functional GdZnAsO, NdZnAsO and PrZnAsO alloys are predicted as half-metallic ferromagnets within a 100% spin-polarization and a total magnetic moment of 14.00, 6.00 and 4.00 μB, respectively that is promising for spintronic applications. The thermoelectric properties and lattice thermal conductivity of REZnAsO alloys are obtained using the Boltzmann transport theory within the constant relaxation time and Slack equation, respectively. The figure-of-merit (ZT) values of GdZnAsO, NdZnAsO, LaZnAsO, CeZnAsO and DyZnAsO alloys are found to be 0.992, 0.996, 0.943, 0.932, 0.980, respectively. These are promising for future thermoelectric applications.

Role of dopants in tuning spintronic features of lithium doped g-C4N3@Lin =1 to 4

We report herein, charge transfer assisted tuning of electronic and spintronic feature of g-C4N3@Lin=1-4 systems. Complete removal of spintronic feature is observed at the doping concentration 14.28%. At lower doping concentration, half metallic feature is observed with clear manifestation of negative differential resistance, which is predominant at n=3. We also noticed significant modifications in current-voltage characteristics as the number of dopants flips from odd to even numbers. Observed feature is mainly attributed to increased charge transfer from Li atom to the g-C4N3 backbone at higher doping concentration and concomitant enhancement in electron-electron interactions. These observations are in corroboration with molecular orbital picture obtained at various doping concentrations.

The electronic, magnetic and half-metallic predictions of Mx (M = Ag, Cd, Y, Zr, Nb, and x = 0, 0.125, 0.25, 1)W1-xSn alloys

ABSTRACT The changes in the magnetic and half-metallic characters of the structures formed by the doping of Ag, Cd, Y, Zr, and Nb atoms at the ratios of x = 0.25 and 0.125 to WSn alloy were investigated. While the spin-up states of all alloys showed metallic character, energy band gaps were observed in the spin-down states, except YSn alloy. Of the 10 structures, 84.10% spin polarization was obtained only in the Zr0.25W0.75Sn alloy, and the spin polarizations were 100% in all remaining alloys. Band calculations were made with both GGA and GGA + mBJ methods. When the GGA + mBJ method was used, an increase in band gaps was observed in proportion to the increase in Fermi energy levels. In addition, the obtained 3, 4, 5, 6, 7 μB/f.u. magnetic moments for M0.25(M = Ag, Cd, Y, Zr, Nb)W0.75Sn alloys, respectively, and the calculated magnetic moment per unit formula of 5.5, 6, 6.5, 7, 7.5 μB/f.u. for M0.125(M = Ag, Cd, Y, Zr)W0.875Sn alloys support their fields that can be used in spintronic applications. The magnetic moment values obtained with GGA-U (U = 1, 2, 3, 4 eV) calculations showed that while the magnetic moment values of Zr0.25W0.75Sn and Nb0.25W0.75Sn alloys were preserved, they directly increased the magnetic moments of some alloys. These high ratios of polarization, band gaps, and magnetic moments make all alloys ideal materials for use in spintronic applications.

Equiatomic quaternary CoXCrAl (X = V, Nb, and Ta) Heusler compounds: Insights from DFT calculations

The half-metallic ferromagnets are likely materials to the spintronics systems for the next generation electronic devices. Among the half-metallic ferromagnetic materials, the equiatomic quaternary Heusler (EQH) compounds get great attention in the recent times. In this study, the EQH CoXCrAl (X = V, Nb, and Ta) compounds are investigated using Density Functional Theory (DFT). The three structural types as type-I, type-II, and type-III, are considered to determine the most stable structural types of CoXCrAl compounds. Furthermore, the three magnetic configurations as paramagnetic (PM), ferromagnetic (FM), and antiferromagnetic (AFM), are studied to find out the most stable magnetic configuration. The type-I FM configuration is the most stable configuration for the CoXCrAl compounds. The calculated electronic band structures reveal that the CoXCrAl compounds are half-metals with metallic behavior in spin-up channel and semiconducting behavior in spin-down channel. Also, the possible d-d hybridizations between the Co, X, and Cr atoms are investigated to show the half-metallic character in detail. Furthermore, the calculated elastic constants satisfy the Born stability criteria, then the CoXCrAl compounds have mechanical stability. Using the determined constants, the mechanical properties are obtained for CoXCrAl compounds. In addition, the dynamical properties are studied and it is found that CoXCrAl compounds are dynamically stable. The structural, magnetic, electronic, mechanic and dynamical properties of CoXCrAl compounds that are the potential candidates for the spintronics applications are presented in this study.

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.

Effect of off-stoichiometric composition on half-metallic character of Co2Fe(Ga,Ge) investigated using saturation magnetization and giant magnetoresistance effect

We investigated the Ge-composition (γ) dependence of the saturation magnetization of Co2Fe(Ga, Ge) (CFGG) thin films and the magnetoresistance (MR) ratio of CFGG-based current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices together with first-principles calculations of the electronic states of CFGG. Theoretical calculations showed that spin polarization is highest at the stoichiometric composition γ = 0.56 in Co2Fe1.03Ga0.41Ge γ and that it decreases in off-stoichiometric CFGG, mainly due to the formation of CoFe antisites for Ge-deficient compositions and FeCo antisites for Ge-rich compositions, where CoFe (FeCo) indicates that Co (Fe) atoms replace the Fe (Co) sites. The saturation magnetic moment (μ s) per formula unit decreased monotonically as γ increased from 0.24 to 1.54 in Co2Fe1.03Ga0.41Ge γ . The μ s was closest to the Slater–Pauling value predicted for half-metallic CFGG at the stoichiometric composition γ = 0.56, indicating that stoichiometric CFGG has a half-metallic nature. This is consistent with the result for the theoretical spin polarization. In contrast, the MR ratio of CFGG-based CPP-GMR devices increased monotonically as γ increased from 0.24 to 1.10 and reached an MR ratio of 87.9% at the Ge-rich composition γ = 1.10. Then, the MR ratio decreased rapidly as γ increased from 1.10 to 1.48. Possible origins for the slight difference between the Ge composition at which the highest MR ratio was obtained (γ = 1.10) and that at which the highest spin polarization was obtained (γ = 0.56) are improved atomic arrangements in a Ge-rich CFGG film and the reduction of effective Ge composition due to Ge diffusion in the GMR stacks.

The half-metallic characteristic of Cr-doped rutile germanium oxide-based dilute magnetic semiconductor predicted by first-principles calculations

The half-metallic characteristic of Cr-doped rutile germanium oxide-based dilute magnetic semiconductor predicted by first-principles calculations

Effect of Structural Disorder on the Physical Properties of the Pd Based Heusler Alloys: PdCoMnAl, Pd2CoAl and Pd2MnAl

In this manuscript, we investigate the effect of structural disorder on the physical properties of Pd-based Heusler alloys: PdCoMnAl, Pd2CoAl and Pd2MnAl using first-principles calculations. In fact, we are studying the structural properties of the equatorial quaternary Heusler alloy PdCoMnAl for three phases: type 1, type 2 and type 3, we have carried out this property to determine the most stable phases. The structural properties results show that the phase of type I, of this alloy is the most stable configuration. In addition, the band structures, and density of states calculations results show that this compound exhibits a half-metallic character with a 100% of spin polarization (SP) at the Fermi-level. The total magnetic moment of the Heusler compound is found to be 5.00 µB. Moreover, it is found that the Slater-Pauling is well described for this alloy. On the other hand, concerning total energy of the full Heusler Pd2YAl (Y = Co or Mn) alloys. It is found that such material in L21-type structure is always smaller than in the XA-type structure during the whole lattice variation variety and the L21-type structure is more energetically preferable for the both full alloys. In addition, the density of states at the Fermi level within the spin up and down states show the metallicity of these compounds. Our results show that the quaternary Heusler is a potential candidate for the spintronic applications.

Persistent half-metallic ferromagnetism in a (111)-oriented manganite superlattice

We employ electronic structure calculations to show that a (111)-oriented (LaMnO3)12∣(SrMnO3)6 superlattice retains a half-metallic ferromagnetic character despite its large thickness. We link this behaviour to the strain and the octahedral connectivity between the layers. This also gives rise to breathing modes, which are coupled to charge and spin oscillations, whose components have a pure eg character. Most interestingly, the magnetisation reaches its maximum value inside the LaMnO3 region and not at the interface, which is fundamentally different from what observed for the (001) orientation. The inter-atomic exchange coupling shows that the magnetic order arises from the double-exchange mechanism, despite competing interactions inside the SrMnO3 region. Finally, the van Vleck distortions and the spin oscillations are crucially affected by the variation of Hund’s exchange and charge doping, which allows us to speculate that our system behaves as a Hund’s metal, creating an interesting connection between manganites and nickelates.

Effective modulating the electronic and magnetic properties of VI3 monolayer: A first-principles calculation

Exploring a two-dimensional ferromagnetic material with a high Curie temperature and large magnetic anisotropy energy is still challenging. Here, we implement an effective adjustment on the electronic and magnetic properties of VI 3 monolayer by means of first-principles calculation. The results indicate that the most stable structure of VI 3 monolayer is particularly susceptible to the calculation parameter such as Hubbard U and the spin-orbit coupling (SOC). Ultimately, under density functional theory (DFT) +U + SOC (U = 3 eV), the most stable structure of VI 3 monolayer is a ferromagnetic semiconductor with a direct band gap of 0.51 eV, and the predicted Curie temperature ( T C ) is 29 K. Biaxial strain and carrier doping could not only induce VI 3 monolayer FM-AFM-FM transition, but also effectively increase T C to 123 K under 0.5 electron doping. Meanwhile, carrier hoping realizes the potential ferromagnetic half-metal. Fortunately, in the constructing alloy monolayer, the VTaI 6 monolayer is found a ferromagnetic half-metal under DFT + U (U = 3, 1 eV for V and Ta), and the T C is increased to 74 K. Moreover, VTaI 6 monolayer possesses a large in-plane magnetic anisotropy energy (IMA) and its physical origin is explained in detail based on the second-order perturbation theory . These findings suggest that VI 3 monolayer has a potential application in the spintronics and high-density magnetic storage devices. • The most stable structure of VI 3 monolayer is very susceptible to the calculation parameters such as Hubbard U value and spin-orbit coupling effect. • Carrier doping can make the VI 3 system generate potential half-metallic characteristics, while biaxial strain maintains its semiconductor properties. • Biaxial strain and carrier doping could not only induce FM-AFM-FM transition, but also carrier doping make T C increase by 3–4 times. • The VTaI 6 monolayer is a FM half-metal and possesses a large in-plane magnetic anisotropy energy (−6.505 meV).

The Temperature Effect on the Physical Properties of CoMnSb Half-Heusler Ferromagnetic: Density Functional Theory and Monte Carlo Simulation

In this work, we have studied the effect of temperature on structural, magnetic, electronic, elastic, thermodynamical properties of half-Heusler CoMnSb by using density functional theory (DFT) and Monte Carlo simulations. The semi-classical Boltzmann transport theory in combination with DFT is implemented to evaluate the thermoelectric (TE) properties. The obtained ground state properties show that CoMnSb has a half metallic character with a magnetic moment value of about 3μ B . Thermodynamical parameters have been studied using quasi-harmonic approximation (QHA) in the range of temperature 0–1000 K. The results of QHA show that the CoMnSb maintain their mechanical stability under temperature. The obtained results of TE properties show that CoMnSb exhibits a low lattice thermal conductivity and that ZT increases with temperature and reaches the maximum value of 0.098 at 1000K. The Monte Carlo simulation is used to investigate the magnetic properties of CoMnSb. Moreover, the transition temperature T C and the hysteresis cycle are calculated. These properties show that the CoMnSb half-Heusler is a good candidate for spintronic applications.

Half-metallic Characteristics of the Novel Half Heusler Alloys XCrSb (X=Ti, Zr, Hf )

Ab-initio calculations are performed to examine the structural, mechanical, electronic, magnetic and thermodynamic properties of the half-Heusler ternary alloys XCrSb (X = H f , Ti, Zr). In this study, the spin-polarized density functional theory (DFT) method that is spin-polarized with generalised gradient approximation (GGA) are used to perform ab-initio calculations to investigate the physical properties of a novel half-Heusler ternary alloys XCrSb (X = H f , Ti, Zr). It was confirmed that the alloys are stable mechanically and exhibit ferromagnetic states (FM). The study reveals that the alloys portray half-metallic character with narrow energy gaps. And it also shows that they have a total magnetic moment of approximately 3ub. From the formation energy calculation, it shows that the alloys can be synthesized experimentally. Also, it was observed that they are mechanically stable. The heat capacities and Debye temperatures were also computed and they show high thermodynamic stability.

Tuning the magnetic and electronic properties of MoI3 monolayer by 3d transition metal doping: A first-principles study

Two-dimensional (2D) materials with intrinsic magnetism have sparked a lot of attention due to their potential applications in spintronics. Recently, monolayer molybdenum triiodide (MoI3), which is a member of the transition metal trihalides (MX3) family, has been predicted to be a stable bipolar ferromagnetic semiconductor (BFMS) with intrinsic magnetism. By means of first-principle calculations based on the GGA + Ueff approach, we modified MoI3 through substitutional doping with 3d transition metal (TM) atoms to improve its spintronic properties. We focused on the study of structural, electronic and magnetic properties of the pristine and 3d TM (TM = Sc, Ti, V, Cr, and Mn) doped MoI3 systems. Our findings reveal that substitutional doping of MoI3 monolayers with Sc and Ti atoms changes their electronic character from a BFMS to a ferromagnetic semiconductor, while V- and Cr-doped MoI3 monolayers result in half semiconducting properties (HSC). More interestingly, the Mn-doped MoI3 monolayer reveals a half-metallic character with enhanced magnetism and sustains these properties even under spin–orbit coupling (SOC). In addition, robust ferromagnetism and high mean-field Curie temperatures were found in all doped systems, especially in the V-doped MoI3 monolayer. By exhibiting these unique electronic and magnetic properties, these TM-doped MoI3 systems could serve as potential candidates for spintronic applications.

First-Principles Study on the Half-Metallicity of New MXene Materials Nd2NT2 (T = OH, O, S, F, Cl, and Br).

This work systematically studied the structure, magnetic and electronic properties of the MXene materials Nd2N and Nd2NT2 (T = OH, O, S, F, Cl, and Br) via first-principles calculations based on density functional theory. Results showed that Nd2NT2 (T = OH, O, S, F, Cl, and Br) have half-metallic characteristics whose half-metallic band gap width is higher than 1.70 eV. Its working function ranges from 1.83 to 6.50 eV. The effects of strain on its magnetic and electronic structures were evaluated. Results showed that the structure of Nd2NT2 (T = OH, O, S, and Br) transitions from a ferromagnetic half-metallic semiconductor to a ferromagnetic metallic and ferromagnetic semiconductor under different strains. By contrast, the structures of Nd2NF2 and Nd2NS2 were observed to transition from a half-metallic semiconductor to a ferromagnetic metallic semiconductor under different strains. Calculations of the electronic properties of different proportions of the surface functional groups of Nd2NT x (T = OH, O, and F; x = 0.5, 1(I, II), and 1.5) revealed that Nd2NO1.5 has the characteristics of semiconductors, whereas Nd2NO(II) possesses the characteristics of half-metallic semiconductors. The other structures were observed to exhibit the characteristics of metallic semiconductors. Prediction of Nd2NT2 (T = OH, O, S, F, Cl, and Br) increases the types of lanthanide MXene materials. They are appropriate candidate materials for preparing spintronic devices.