Half-metallic Character Research Articles

Structural, electronic, magnetic and thermoelectric properties of full heusler alloys Co2YZ (Z = S, Ge, Se): A first principles calculation

Density functional theory (DFT) calculations are used to find physical characteristics of full Heusler (FH) alloys Co2YZ (Z = S, Ge, Se). Full potential-linearized augmented plane wave (FP-LAPW) method within generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof functional is used. The results of phase stability have confirmed the stability of ferromagnetic (FM) phase as compared to anti-ferromagnetic (AFM), and nonmagnetic (NM) phases. The electronic properties show the half metallic (HM) character of Co2YS and Co2YSe by GGA. The role of on-site coulomb interaction (U) is also checked by GGA + U approach for Co2YGe which confirmed its HM nature. The band diagrams are in accordance to density of states (DOS). The total magnetic moment (MM) of all alloys is 3μB which is in agreement to Slater-Pauling Rule (SPR). The spin polarization (SP) indicated that these materials are completely spin polarized. The Seebeck coefficient (S) and electrical conductivity (σ) are also calculated and discussed.

Tuning the electronic and magnetic properties of monolayer germanium triphosphide adsorbed by halogen atoms: Insights from first principles study

Abstract Using first-principles calculations, we explored the adsorption effects on the electronic and magnetic properties of halogen atoms (F, Cl, Br, and I) on monolayer germanium triphosphide (GeP3). After adsorption, the binding energies of all adsorbed systems are extremely low, which implies a remarkable thermodynamic stability. A significant charge transfer from the monolayer GeP3 to the halogen atoms occurs, resulting in a stable P-type doping. Besides, the work function of monolayer GeP3 can be effectively tuned by the adsorption of the halogen atoms (F, Cl, Br, and I). The system adsorbed by halogen atoms can induce the spin polarization band structures. Particularly, F, Cl, and Br atoms adsorbed GeP3 monolayer all show a metallic character, whereas the adsorption of I results in an interesting half-metallic character. The calculations also show that the pristine monolayer GeP3 is non-magnetic (NM), whereas all adsorbed configurations show a significant ferromagnetic (FM) character. Additionally, the binding energies of adsorbed GeP3 monolayers can be efficiently modified when applying an electric field from 0 V/A to 1 V/A. These valuable findings imply that the halogen atoms adsorbed GeP3 monolayer holds valuable potential for the design of spintronic nano-devices.

Insight view of Hf2CrZ (Z = B, Ga, In, Si, Ge, Sn) Heusler materials via DFT calculations: A study on structural, electronic and magnetic properties

In this study, we have investigated the structural, electronic and magnetic properties of the Hf2CrZ (Z = B, Ga, In, Si, Ge, Sn) full Heusler materials in both Hg2CuTi and Cu2MnAl type structures. These investigations have been carried out by employing the first-principles computational method - full potential (FP) linearized (L) augmented plane-wave plus local orbital (APW + lo) - framed within the density functional theory (DFT) and embodied in WIEN2k computational package. Our investigations show that Cu2MnAl-type structures of the Hf2CrZ (Z = B,Ga,In, Si, Ge, Sn) Heusler compounds are more stable than that of Hg2CuTi-type ones. Our investigations also show that Hg2CuTi type structure of Hf2CrZ Heusler alloys demonstrates half-metallic character for Hf2CrZ (Z = B,Ga, In) with a value of the magnetic moment 1 μB and lower value for Hf2CrZ (Z = Si, Ge, Sn).

Ab Initio Investigations of the Structural, Electronic, Magnetic, and Thermal Properties of Cr2TaGe1-xSnx Quaternary Heusler Alloys

The first-principle calculations were performed in the framework of the density functional theory (DFT) using FP-LAPW method as implemented in Wien2k code to determine the structural stability, electronic, and magnetic properties of quaternary Heusler alloys Cr2TaGe1-xSnx (x = 0, 0.25, 0.50, 0.75, 1.00), The results showed that for the compounds, the AlCu2Mnl-type structure is energetically more stable than CuHg2Ti-type structure at the equilibrium volume. The calculated lattice constants for Cr2TaGe and Cr2TaSn are 6.081 A and 6.311 A, respectively. For mechanical properties, shear modulus, Young’s modulus, elastic constants, Poisson’s ratio and shear anisotropy factor have studied. Their obtained values reveal that these compounds are mechanically stable. The electronic band structures and density of states of our compounds show a half metallic character with total magnetic moments, − 3.00 μB per formula unit with indirect band gap, 0.569 eV and 0.482 eV for Cr2TaGe and Cr2TaSn respectively. Regarding thermal properties such as the thermal expansion coefficient, heat capacity, and Debye temperature, we have applied a very suitable model for studying thermodynamics quantities called the quasi-harmonic Debye model. On the basis of these results, these alloys are predicted to be good candidates for future spintronic applications.

Electronic and magnetic properties of 3d transition metal atom adsorbed Zr2CO2 Mxene: First-principles study

The structural, electronic and magnetic properties of the 3d transition metal (TM) atoms (from Sc to Zn) adsorbed Zr2CO2 Mxenes were investigated systematically by using first-principles calculations. The adsorption energies demonstrate that all the TM atoms are chemically adsorbed above the C atom (TC) sites of the Zr2CO2 Mxenes except for the Zn atom. Furthermore, the analyses of bond length, charge transfer and vDW interaction ratio demonstrate that the interaction between adatoms (from Sc to Cu) and under-coordinated atoms is mainly covalent bonding features. Cu adsorbed Zr2CO2 Mxene exhibits nonmagnetic metal, and Ni and Zn adsorbed systems show nonmagnetic semiconductor. While Sc, V, Cr, Mn and Co adsorbed Zr2CO2 Mxenes exhibit magnetic metal. Interestingly, the Fe adsorbed system shows bipolar magnetic semiconductor character. Especially, the Ti adsorbed system exhibits half-metallic character. Our results demonstrate that the 3d TM atom adsorbed Zr2CO2 Mxene could provide various potential application in nanoelectronics and spintronics.

Predictions on structural, electronic, magnetic and thermal properties of new Heusler alloys Cr$$_{{{2}}}$$NbSi$$_{{1-x}}$$Ge$$_{{x }}$$ from first-principles calculations

In this study, by using full-potential linearised augmented plane wave (FP-LAPW) method with the generalised gradient approximation (GGA) based on density functional theory (DFT), the structural, electronic, elastic and magnetic properties of the Heusler alloys Cr $$_{\mathrm {2}}$$ NbSi $$_{{1-x}}$$ Ge $$_{x}$$ have been evaluated. The AlCu $$_{\mathrm {2}}$$ Mnl-type structure is more stable than the CuHg $$_{\mathrm {2}}$$ Ti-type structure at equilibrium volume for the compounds. The ground-state properties of our alloys including the lattice parameter and bulk modulus were calculated. In view of Poisson’s and Pugh’s ratio, the ductility and brittleness of Cr $$_{\mathrm {2}}$$ NbSi $$_{{1-x}}$$ Ge $$_{x}$$ has been analysed. The mechanical stability is maintained throughout the pressure range with high value of Debye temperature. The electronic band structures and density of states of our compounds show a half metallic character with total magnetic moments, −3.00 $${\mu }_{\mathrm {B}}$$ per formula unit with indirect band gap, $$E_\mathrm{g}$$ $$=$$ 0.152 eV and 0.262 eV for Cr $$_{\mathrm {2}}$$ NbSi and Cr $$_{\mathrm {2}}$$ NbGe respectively. Furthermore, we have analysed the thermal properties by the quasi-harmonic Debye model. Through the obtained results, we can say that these compounds can be strong candidates for future spintronic applications.

A DFT study of structural, magnetic, elastic and optoelectronic properties of lanthanide based XAlO3 (X=Nd, Gd) compounds

Full potential linearized augmented plan wave (FP-LAPW) method based on density functional theory (DFT) is employed to investigate the structural, optoelectronic, elastic and magnetic properties of cubic XAlO3 (X = Nd, Gd) perovskites. The optimized unit cells have been used to expose the thermodynamic stability in the ferromagnetic ground state, which is further verified in terms of enthalpy of formation (ΔHf) and cohesive energy. The spin polarized band structure and density of states illustrate that NdAlO3 perovskite has a half metallic character, and GdAlO3 has a semiconductor nature. The bulk modulus, elastic constants, Poisson's ratio, shear modulus, anisotropy and Young's modulus are also determined. The calculated magnetic moments of cubic NdAlO3 and GdAlO3are 3 μB and 7 μB, respectively and the magnetization is largely originated from Nd and Gd atoms. Furthermore, the optical parameters like reflectivity, optical conductivity, dielectric constants, absorption coefficient and refractive index are also investigated. The results suggest that these compounds could be promising materials for spintronic and optoelectronic devices.

Investigation Insights into Electronic Structures, Exchange Splittings, Induced Ferromagnetism, and Half-Metallic Feature in New Ti-Doped BaS

The new Bai-xTixS compounds based on the titanium (Ti)-doped BaS at various concentrations x = 0.25, 0.5 and 0.75 were characterized using the first-principle concepts of density functional theory. We investigated the doping effect of titanium on the structural and electronic properties, induced ferromagnetism, half-metallicity and exchange splittings in Ba1-xTixS materials. The origin of ferromagnetism in the Ba1-xTixS compounds is due to the localized partially occupied 3d (Ti) states related to the double exchange mechanism. The electronic structures of Ba1-xTixS at concentrations x = 0.25 and 0.5 show half-metallic ferromagnetic character with spin polarization of 100%. For concentration x = 0.75 the Ba0.25Ti0.75S exhibits a metallic nature for two spins channels due to widening 3d (Ti) states in the gap. Therefore, Bai-xTixS at concentrations x = 0.25 and 0.5 seems to be potential candidat for spintronics.

Electronic structures, magnetic properties and mechanical stability of half-metallic quaternary Heusler CoMnVTe

The electronic structures, magnetic properties and mechanical stability of three configurations of a promising half-metallic quaternary Heusler compound CoMnVTe were systematically and comprehensively studied by the first-principle calculations. The results show that type-I and type-II configurations present half-metallic behavior with 100% spin polarization. Especially the type-I configuration has the most stable structure among these three configurations. The type-I, type-II configurations can maintain the half-metallic character within the lattice constant 5.47–6.12 A and 5.82–6.23 A, respectively. Anisotropy factor and three-dimensional (3D) Young’s modulus indicate that these three configurations of CoMnVTe compound are anisotropic. The type-I and type-II configurations own stable mechanical properties in some and all half-metallic lattice constant regions, respectively. The test results of strong correlation correction show that the U value has a visible effect on the half-metallic properties of the title compound. The (001)@VTe and (111)@V surfaces of type-I configuration also have half-metallic properties. The robust half-metallic properties and mechanical stability make the quaternary Heusler compound CoMnVTe a promising candidate for spintronic devices.

The structural, electronic, magnetic, and optical properties of the Cr-, Mo-, and W-doped ZnTe alloys

The first-principle method is adopted to study doping of different atoms X (X = Cr, Mo, or W) in ZnTe compound. The spin-down bandgaps of the X-doped Zn0.96875X0.03125Te alloys are 1.368, 1.415, and 1.399 eV for X = Cr, Mo, and W, respectively. All the doped Zn0.96875X0.03125Te (X = Cr, Mo, or W) alloys presents half-metallic (HM) feature, which is different from the ZnTe semiconductor, thus the doped HM alloys are the potential materials for spintronic applications. The Cr-3d(t2g) and Te-5p spin-up states of the Zn0.96875Cr0.03125Te alloy intersect the Fermi level, but only the Mo-4d(t2g) and W-5d(t2g) spin-up states of the Zn0.96875Mo0.03125Te and Zn0.96875W0.03125Te alloys, respectively, intersect the Fermi level. For the Zn0.96875Cr0.03125Te alloy, the double-degenerate $$d_{yz}$$ and $$d_{xz}$$ spin-up states of Cr atom are occupied, but the undegenerated $$d_{xy}$$ states of Cr atom are unoccupied. But for Zn0.96875X0.03125Te (X = Mo or W) alloys, the threefold degenerate $$d_{xy}$$ , $$d_{yz}$$ , and $$d_{xz}$$ states of X atoms are half-occupied. All the X-doped Zn0.96875X0.03125Te (X = Cr, Mo, or W) alloys are magnetic with the total magnetic moments of 4.000 $$\mu_{{\text{B}}}$$ mainly contributed by the X atom and neighboring Te atoms. The doped Zn0.96875X0.03125Te (X = Cr, Mo, or W) alloys have promising applications in infrared devices.

Ferromagnetic coupling and the effect of Fe-dt2g state on ferromagnetism in half-metallic ZnO:Fe

Based on first principle calculations using GGA + U approach, we have studied the origin of room-temperature ferromagnetism in Fe-doped ZnO. The ferromagnetic coupling and the contribution of Fe-d states on the ferromagnetism of ZnO are also studied. The p–d exchange interaction between the Fe-d and O-p states is responsible for the ferromagnetism at lower Fe concentration in ZnO; whereas at the higher concentration, the enhanced short-range antiferromagnetic coupling between Fe ions dominates over ferromagnetism. The DOS results depict that the Fe-dt2g state predominantly contributes the hybridization at the fermi level resulting the magnetism in the Fe-doped ZnO system. The total energy calculations reveal the existence of short-range ferromagnetic coupling in the system. The band structure results depict the half-metallic character of the system with spin-polarized nature.

Structural, thermo-elastic, electro-magnetic and thermoelectric attributes of quaternary CoNbMnX (X = Al, Si) Heusler alloys

This investigation consists of performing the structural, thermodynamic, electronic, magnetic and thermoelectric characteristics of the quaternary Heusler CoNbMnX (X = Al, Si) alloys using DFT within Wien2k code. Our calculations show that the atomic arrangement of the two alloys CoNbMnAl and CoNbMnSi is Type-I. From the elastic constant and the formation energy values, these compounds are predicted to be mechanically and thermodynamically stable, thus can be formed experimentally. The calculated values of their bulk modulus and cohesive energy values show that CoNbMnSi is more rigid than CoNbMnAl. From the analysis of the electronic properties, CoNbMnAl is identified to be paramagnetic and semiconductor alloy with 0.15 eV narrow indirect (Γ-X) band gap. Whereas, CoNbMnSi is characterized as a ferromagnetic alloy with half-metallicity character having a total magnetic moment of 1μB. The charge density contours and Fermi surface, predict a combined covalent and ionic bond between the atoms of CoNbMnX alloys. The calculated thermoelectric parameters assume that these alloys tend to behave as p-type with the same thermoelectric efficiency for either charge carriers; hole or electron. Depending on the high Seebeck coefficient value and ZT = 1 of the present alloys, potential applications are predicted, such as spin injection materials and spintronic applications.

Half-metallic ferromagnetism study of quaternary fluoro-elpasolite Rb2NaCrF6

In this work, we have predicted the structural, electronic, and magnetic properties of the quaternary fluoro-elpasolite Rb2NaCrF6 alloy. We have performed our calculations by the use of first-principle methods developed on spin-polarized density functional theory, where the electronic exchange–correlation potential is evaluated by the generalized gradient approximation GGA-PBEsol coupled with the improved TB-mBJ approach. The calculated structural parameters of Rb2NaCrF6 are in good agreement with the available experimental data. Rb2NaCrF6 exhibits a half-metallic ferromagnetic feature with a spin polarization of 100% at the Fermi level and a direct large half-metallic gap of 2.04 eV. The total magnetic moments are 3μB. This compound is half-metallic ferromagnets, and it can be potential candidates for spintronics applications at a higher temperature.

First-principles Study of a Half-metallic Ferrimagnetic New Full-Heusler Mn2OsGe Alloy

Full-Heuslers are a group of materials that have repeatedly attracted the curiosity of scientists and researchers, especially for their use in the field of spintronics. In this work, we undertook a study on the structural, elastic, electronic, magnetic and thermodynamic properties of the full-Heusler Mn2OsGe alloy using the calculations of the first principles. Two approximations are used: the generalized approximation of the Perdew–Burke–Ernzerhof GGA–PBE gradient for electron-correlation exchange and the new modified Tran-Blaha form of the modified Becke-Johnson mBJ–GGA-PBE potential. As important results, we found that the compound Mn2OsGe is stable in the CuHg2Ti structure; on the other hand, we could also verify its mechanical stability at zero temperature and pressure. For the calculation of the electronic properties, we were able to determine the half-metallic ferrimagnetic character of our compound, which exhibits a metallic behavior in the state of the majority spins, and a semiconductor behavior in the state of the minority spins. An integer value of 2[Formula: see text][Formula: see text] has been recorded for a magnetic moment and this conforms to the Slater–Pauling rule.

Two-dimensional hexagonal manganese carbide monolayer with intrinsic ferromagnetism and half-metallicity

Recent experimentally observed intrinsic ferromagnetism in two-dimensional (2D) van der Waals crystals has ignited substantial interests due to their great potential in spintronic devices. However, their practical applications are hampered by rather low Curie temperature and small magnetic anisotropic energy. Here, we predict from first-principles calculations that the 2D pristine hexagonal manganese carbide (h-MnC) sheet exhibits robust ferromagnetic and half-metallic features with complete spin polarization, sizable magnetic anisotropic energy, and wide half-metallic gap near the Fermi energy level. Moreover, the h-MnC sheet can retain its structure up to the temperature of 1000 K, indicating a highly thermodynamic stability. The Monte Carlo simulations based on the Heisenberg model with single-ion anisotropy predict a Curie temperature of 233 K in 2D h-MnC crystal. We confirm the robustness of the ferromagnetism and half-metallicity against the external strain from −6% to 10%. Also, a feasible experimental fabrication route is proposed to realize the h-MnC monolayer via heterostructure engineering and exfoliation techniques. Overall, the robustness of the half-metallicity in combination with the high-temperature ferromagnetism render the freestanding h-MnC monolayer and even its energetically favorable h-MnC/MoS2 and h-MnC/MoSe2 heterostructures quite promising materials for developing practical spintronic nanodevices.

Induced ferromagnetism in bilayer hexagonal Boron Nitride (h-BN) on vacancy defects at B and N sites

We investigated the electronic and optical properties of bilayer AB stacked Boron and Nitrogen vacancies in hexagonal Boron Nitride (h-BN) using density functional theory (DFT). The density of states (DOS) and electronic band structure showed that Boron vacancy in bilayer h-BN results in a magnetic and conducting ground state. The band gap energy ranges from 4.56 eV for the pristine BN bilayer to 0.12 eV for a single Nitrogen vacancy in the bilayer. Considering the presence of 1,3,4-Boron vacancy, half metallic character is observed. However, the 2-boron vacancy configuration resulted in metallic character. The bilayers with 1,2,3,4- Nitrogen vacancy has a band gap of 0.39, 0.33, 0.28 and 0.12eV respectively, which is significantly less than the pristine band gap. Also B and N vacancy induces ferromagnetism in the h-BN bilayer. The maximum total magnetic moment for the Boron vacant system is 6.583uB in case of 4-Boron vacancy configuration. In case of Nitrogen vacancy system it is 3.926uB for 4-Nitrogen vacancy configuration. The optical response of the system is presented in terms of the absorption coefficient, refractive index and dielectric constant for pristine as well as the defective configurations. Negative value of dielectric constant for Boron vacant system in the energy range 0.9-1.4 eV and for Nitrogen vacant system in the energy range 0.5-0.8 eV opens an opportunity for it to be utilized for negative index optical materials. The current study shows that B and N vacancies in bilayer h-BN could have potential applications in nano-structure based electronics, optoelectronics and spintronic devices.

Study of Half Metallic Ferromagnetism and Optical Properties of Mn-Doped CdS

The spin-polarized electronic band structures, density of states and optical and magnetic properties of dilute magnetic semiconductors (DMSs) Cd1−xMnxS with 6.25%, 12.5% and 25% concentrations of Mn have been studied by using ab initio calculations. The electronic band structures show half metallic ferromagnetic (HMF) behaviour with direct band gap at Γ symmetry point. The calculated values of band gaps are 0.8 eV, 0.99 eV, 1.3 eV and 1.5 eV for CdS, Cd0.9375Mn0.0625S, Cd0.875Mn0.1250S and Cd0.75Mn0.25S, respectively. The energy gap of CdS was found to increase by doping with transition metal impurity. The addition of the dopant atoms in CdS turns it into a p-type semiconductor. This half metallic character makes these compounds a potential candidate for spintronics applications. In optical properties, the role of Mn concentration on the absorption coefficient, optical conductivity, refractive index, extinction coefficient and dielectric function has been investigated. The total magnetic moment is found approximately 5.000 μB per dopant atom for Cd1−xMnxS (x = 6.25%, 12.5% and 25%). This value indicates that every Mn impurity adds no hole carriers to the perfect CdS crystal.

Bandgap engineering of the (001) oriented thin-films of the Heusler alloys Co2‒xFexCrAl (x=0.00, 0.25, 0.50, 0.75 or 1.00)

Materials which possess 100% spin-polarization (SP) at their thin-film form are essential for spintronic devices. The half-metallicity has been predicted theoretically in many Co-based Heusler alloys thin-films. Especially the Heusler alloy Co2CrAl has been studied extensively. A previous study reported that the CrAl terminated (001) oriented thin-film had 84% SP, while the other study reported that the CrAl terminated (001) oriented thin-film had 100% SP. Therefore, we investigate in detail the effects of the Fe-doping on the structural, electronic and magnetic properties of the bulk Heusler alloys Co2‒xFexCrAl (x=0.00, 0.25, 0.50, 0.75 or 1.00) and their various terminated (001) oriented thin-films. All the bulk Heusler alloys Co2‒xFexCrAl and their x-CrAl terminated (001) oriented thin-films possess half-metallicity and 100% SP at the Fermi level EF. The surface energy Es of the x-CrAl terminated (001) oriented thin-films increases with Fe-doping concentration x. The CrAl terminated (001) oriented thin-films of the Heusler alloys Co2‒xFexCrAl (x=0.00, 0.25, 0.50, 0.75 or 1.00) maintain the half-metallic (HM) character and 100% SP and thus can be used in spintronic devices, especially the 0.50-CrAl terminated (001) oriented thin-film with the largest spin-down bandgap Eg↓ of 0.213 eV and the largest HM bandgap EgHM of 0.106 eV.

Half-metallicity in [formula omitted] and V doped tin-carbide SnC

Electronic and magnetic properties of V and Mn doping SnC are investigated in this work. The ab-initio structure calculation based on the Korring-Kohn-Rostoker (KKR) method combined with the coherent potential approximation (CPA) have been used. We have found that the substitution of Sn atoms in Tin-Carbide by Mn and V Transition Metals brings a half-metallic ferromagnetic character with a double exchange mechanism. The partial moments of impurities in the compound varies slightly from 1.11 to 1.09 μB in V case and 3.56 to 3.5 μB for Mn case. While the polarization is found to be equal 100%, in both cases where the up-spins channel is conductive, while the down channel is insulating. Using the Vegard's law, we have determined the laticce parameter of the doping compounds as function of the impurities concentrations. Such features has a significant implications for the performance of spintronic instruments and boosts their magnetoresistance ability at an enormous rate. Hence, the critical temperature can be controlled by varying the concentration of impurities.

Spinelectronic investigation of the quaternary vanadium fluoride Rb2NaVF6: Ab-initio method

In this study, we have investigated the structural, electronic, and magnetic properties of the Rb2NaVF6 compound. We have performed our calculations by the use of first-principle methods based on spin-polarized density functional theory, where the electronic exchange-correlation potential is treated by the generalized gradient approximation GGA- PBEsol coupled with the improved TB-mBJ approach. The calculated structural parameters of Rb2NaVF6 are in good agreement with the available experimental data. Rb2NaVF6 exhibits a half-metallic ferromagnetic feature with a spin polarization of 100 % at the Fermi level and a direct large half-metallic gap of 3.582 eV. The total magnetic moments are 2 μB. This material is half-metallic ferromagnets, and it can be potential candidates for spintronics applications at a higher temperature.