Total Spin Magnetic Moment Research Articles

First-principles investigation of spin characteristics and thermoelectric properties in Ba2SmMoO6 and Ba2EuMoO6 double perovskites

This investigation employs first-principles calculations with the Generalized Gradient Approximation (GGA) and modified Becke-Johnson (mBJ) exchange-correlation functionals, employing the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method. The main objective is to investigate the double perovskites Ba2SmMoO6 and Ba2EuMoO6. We conduct a thorough analysis of the structural, electrical, magnetic, thermoelectric and optical properties of these materials. Both compounds are stable in ferromagnetic phase, according to structural studies. Ba2SmMoO6 has a 3.80 eV energy gap, aligned with the W-X direction, which exhibits half-metallic behavior. On the other hand, Ba2EuMoO6 has a 3.03 eV energy gap that is directly aligned with the X-X direction, using mBJ-GGA. Magnetic investigation revealed a total spin magnetic moment of 7 μB for Ba2EuMoO6, mainly due to Eu (5.98 μB) and 6 μB for Ba2SmMoO6, mainly due to Sm (4.53 μB). It was found that both materials have high Seebeck coefficients and electrical conductivities at high temperatures, with performance improving with temperature. However, the figure of merit (ZT) approaches a value of one, indicating their potential for use in thermoelectric applications at high temperatures. Ba2SmMoO6 and Ba2EuMoO6 are identified as highly favourable options for effective thermoelectric devices. The high UV absorption, the unique refractive and reflective properties offer potential in photonics, optical coatings, and other fields requiring precise light manipulation.

Investigating Structural, Mechanical, Electronic and Magnetic Properties of Spin-Gapless Quaternary Heusler Alloy Crmnval

Utilizing density functional theory (DFT), the study thoroughly investigates the equiatomic quaternary Heusler compound CrMnVAl, revealing its promising properties across multiple domains. The energy minimization curve shows its structural stability with lattice parameter 5.91Å in ferromagnetic phase. The negative values of formation and cohesive energy indicate its chemical stability, while electronic structure analysis demonstrates spin gapless semiconducting behavior. The total spin magnetic moment of this compound is almost 3.00 μB obeying the Slater-Pauling 18 electron rule (Mt = Zt – 18). The 100% spin polarisation and the Curie temperature higher than ambient temperature indicate that this compound acts as a promising material for spin dependent applications. Furthermore, exploring its mechanical properties complements these findings, offering insights into its structural integrity and suitability for diverse applications. Overall, the study underscores CrMnVAl's potential as a versatile material for spintronics and beyond.

Investigation of Electronic Structure, Magnetic, Mechanical, Thermodynamic, Thermoelectric, and Optical Properties of Half‐Metallic V2MnSb and V2FeSb Heusler Alloys

The structural, magnetoelectronic, mechanical, thermodynamical, thermoelectric, and optical properties of V2XSb (X = Mn, Fe) alloys are simulated using density functional theory. The structural optimization is done in Hg2CuTi prototype structure with F‐43m space group and confirms its stability in ferromagnetic state. The generalized gradient approximation and modified Becke–Johnson (mBJ) method are used to depict the half‐metallic nature of these alloys. Using Tran Blaha's mBJ potentials, the estimated indirect bandgap along the symmetry points is 0.54 eV for V2MnSb and 0.56 eV for V2FeSb. The total spin magnetic moments of V2XSb (X = Mn, Fe) are 3 and 2 μB which are in accordance with the Slater–Pauling rule. The mechanical stability reveal the ductile nature. The thermodynamic properties are calculated to determine the effect of temperature and pressure. The optical properties of these Heusler alloys are investigated to determine the absorbing power and optical conductivity. Using Boltzmann transport theory, thermoelectric parameters such as Seebeck coefficient and electrical conductivity are also depicted. The designated compound V2XSb (X = Mn, Fe) is unique due to the fact that that it has a high figure of merit (ZT) at both high and low temperatures, which is a beneficial parameter for converting squandered heat energy into beneficial energy that preserves the environment and is free of global warming and other hazardous substances.

DFT study of the half‐metallic variant perovskites A2OsX6 (A = Rb/Cs; X = Cl/Br) for spintronic and thermoelectric applications

AbstractWe present our results of the spin‐polarized calculations on the structural, magneto‐electronic, thermodynamic, and thermoelectric properties of vacancy‐ordered double perovskites A2OsX6 (A = Rb/Cs; X = Cl/Br). We utilized the Wu‐Cohen generalized gradient approximation (Wu‐GGA) and the mBJ scheme to determine a more reliable electronic structure. The compounds exhibit negative formation energy, suitable tolerance factor, and a stable phonon spectrum, indicating their stability. The compounds show half‐metallicity, acting as semiconductors with direct band gaps between 2 and 3 eV in the spin‐up orientation while metallic in the spin‐down. Each compound shows a total spin magnetic moment of 2.00 μB per formula unit, with Os‐t2g states contributing the most (~1.5 μB). The computed thermoelectric coefficient indicates the usability of these compounds across a wide temperature range (200–800 K) with high electrical conductivity and low electronic thermal conductivity. The compounds exhibit high Seebeck coefficient and figure of merit (ZT), making them suitable for thermoelectric applications. With ferromagnetic and half‐metallic characteristics, these compounds could be promising candidates for spintronics, thermoelectronic, and data storage applications.

The impact of molybdenum and tungsten co-doping on the physical properties of CeO2: First-principles calculations

In this study, the WIEN2k code, utilizing the full potential linearized augmented plane wave (FPLAPW) approach within the framework of density functional theory (DFT), explicitly employing the PBEsol approximation, is employed to investigate the fundamental properties of W-doped and (Mo, W) co-doped cubic CeO2. Herein, lattice constants, bulk modulus and cell volumes were evaluated for structural properties. The total density of states (TDOS) for various doped and co-doped CeO2 systems was used to explain the origin of magnetic behavior. The band structure (BS) calculations show that the doped and co-doped materials exhibit semiconductor behavior with a direct bandgap in both spin channels. The calculated total spin magnetic moments of W/CeO2 and (Mo, W)/CeO2 alloys are 2.002[Formula: see text][Formula: see text] and 4.007[Formula: see text][Formula: see text] respectively. Furthermore, the optical absorption shows absorption peaks in the visible range and a redshift. As a result, adding molybdenum and tungsten additives improves the electro-optical properties of previous materials.

First-principles study on rare earth-based equiatomic quaternary Heusler alloys YbCoCrSb and YbCoTiSn: New candidates for spintronics

We have investigated the structural, mechanical, thermal, electronic, magnetic, and half-metallic properties of new Yb-based EQHAs such as YbCoCrSb and YbCoTiSn using first-principles calculations. We computed the ground state properties of different possible crystal structures and magnetic states. We also calculated their elastic constants and derived mechanical parameters, including bulk, shear, and Young's moduli, as well as Poisson's and Pugh ratios. The electronic structure of both EQHAs shows half-metallic behavior with a spin down band gap of 0.39 eV for YbCoCrSb and 0.30 eV for YbCoTiSn in the GGA-PBE scheme. The estimated total spin magnetic moment has a positive integer value, which is well in accordance with the Slater-Pauling rule of 18. Because of the nearly closed f orbital shell of the Yb atom, the total spin magnetic moment is mainly dependent on 3d transition metal atoms. These alloys exhibit TC > 300 K using the mean field approximation.

Defective ZrSe2: a promising candidate for spintronics applications

The current study presents the electronic and magnetic properties of monolayer ZrSe2 nanoribbons. The impact of various point defects in the form of Zr or Se vacancies, and their combinations, on the nanoribbon electronic and magnetic properties are investigated using density functional theory calculations in hydrogen-terminated zigzag and armchair ZrSe2 nanoribbons. Although pristine ZrSe2 is non-magnetic, all the defective ZrSe2 structures exhibit ferromagnetic behavior. Our calculated results also show that the Zr and Se vacancy defects alter the total spin magnetic moment with D6Se, leading to a significant amount of 6.34 µB in the zigzag nanoribbon, while the largest magnetic moment of 5.52 µB is induced by D2Se−2 in the armchair structure, with the spin density predominantly distributed around the Zr atoms near the defect sites. Further, the impact of defects on the performance of the ZrSe2 nanoribbon-based devices is investigated. Our carrier transport calculations reveal spin-polarized current-voltage characteristics for both the zigzag and armchair devices, revealing negative differential resistance (NDR) feature. Moreover, the current level in the zigzag-based nanoribbon devices is ∼10 times higher than the armchair devices, while the peak-to-valley ratio is more pronounced in the armchair-based nanoribbon devices. It is also noted that defects increase the current level in the zigzag devices while they lead to multiple NDR peaks with rather negligible change in the current level in the armchair devices. Our results on the defective ZrSe2 structures, as opposed to the pristine ones that are previously studied, provide insight into ZrSe2 material and device properties as a promising nanomaterial for spintronics applications and can be considered as practical guidance to experimental work.

High Spin Magnetic Moments in All-3d-Metallic Co-Based Full Heusler Compounds.

We conduct ab-initio electronic structure calculations to explore a novel category of magnetic Heusler compounds, comprising solely 3d transition metal atoms and characterized by high spin magnetic moments. Specifically, we focus on Co2YZ Heusler compounds, where Y and Z represent transition metal atoms such that the order of the valence is Co > Y > Z. We show that these compounds exhibit a distinctive region of very low density of minority-spin states at the Fermi level when crystallizing in the L21 lattice structure. The existence of this pseudogap leads most of the studied compounds to a Slater-Pauling-type behavior of their total spin magnetic moment. Co2FeMn is the compound that presents the largest total spin magnetic moment in the unit cell reaching a very large value of 9 μB. Our findings suggest that these compounds are exceptionally promising materials for applications in the realms of spintronics and magnetoelectronics.

Slater-Pauling Behavior in Half-Metallic Heusler Compounds.

Heusler materials have become very popular over the last two decades due to the half-metallic properties of a large number of Heusler compounds. The latter are magnets that present a metallic behavior for the spin-up and a semiconducting behavior for the spin-down electronic band structure leading to a variety of spintronic applications, and Slater-Pauling rules have played a major role in the development of this research field. These rules have been derived using ab initio electronic structure calculations and directly connecting the electronic properties (existence of spin-down energy gap) to the magnetic properties (total spin magnetic moment). Their exact formulation depends on the half-metallic family under study and can be derived if the hybridization of the orbitals at various sites is taken into account. In this review, the origin and formulation of the Slater-Pauling rules for various families of Heusler compounds, derived during these two last decades, is presented.

Phosphorus, cobalt‐phosphorus, and nickel‐phosphorus clusters: Growth behavior, electronic, and magnetic properties

AbstractThe equilibrium geometries, and electronic and magnetic properties of phosphorus, cobalt‐phosphorus, and nickel‐phosphorus (Pn+1, CoPn, and NiPn, n = 1–24) clusters have been investigated by using first principle calculations. The doping with cobalt or nickel atom favors the endohedral structures in which the metal atom is encapsulated inside the phosphorus framework, while geometrical structures are metal‐dependent. The growth pattern behaviors and stabilities are examined from the binding energies, the second‐order energy differences, and the HOMO–LUMO gaps. The doping with Co or Ni atom contributes to strengthening the stability of the phosphorus frame with a marked improvement in the case of Ni atom. The total spin magnetic moment is enhanced with doping with Co atom. In contrast, the magnetic moment is quenched in the case of NiPn. Vertical electron affinities and ionization potentials are also reported and discussed.

Structure and stability of Mo-doped Cun (n = 1–12) clusters: DFT calculations

The thermodynamic and chemical stability of CunMo (n = 1–12) clusters are evaluated by density functional theory (DFT) calculations. The most stable structures are obtained by using the SCG (systematic growth algorithm) and corroborated by simulated annealing. The lowest-energy structures of CunMo clusters are planar and quasiplanar for n = 3–7, while icosahedral-like structures for n = 8–12. The relative stability of the clusters is further analyzed through the average binding energy, the fragmentation energy and second-order energy differences. The results of EB shows that doping with Mo slightly reduces the stability of small clusters with n = 1–7, however, for n = 8 onward, the doped clusters become more stable due to the formation of the icosahedral structure at Cu12Mo. The results show that Cu4Mo, Cu7Mo, Cu9Mo and Cu12Mo, are more stable than the neighbor clusters. In addition, the doped clusters show higher HOMO–LUMO gaps and total spin magnetic moments compared to pure Cun clusters. The IR spectra of the clusters are provided.

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

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

Ab initio prediction of half-metallicity in the NaMnZ2 (Z = S, Se, Te) ternary layered compounds

Motivated by recent theoretical studies predicting half-metallicity in some ternary manganese chalcogenides, first-principles calculations based on spin-polarized density functional theory (DFT) are applied to investigate the structural, elastic, electronic and magnetic properties of the ternary layered compounds NaMnZ2 (Z = S, Se, Te). We assume for all compounds the experimentally determined, in the case of NaMnSe2 and NaMnTe2 compounds, noncentrosymmetric trigonal structure (space group P3m1; no. 156). The analysis of spin-polarized band structures and of the diagrams of density of states reveals the half-metallic character of the considered materials. We find that the strong spin polarization of the d orbitals of the manganese atoms is at the origin of the ferromagnetism of these compounds with a total magnetic moment per formula unit of 4μB. The studied compounds show a Slater-Pauling behavior and the total spin magnetic moment per cell (Mt) evolves with the total number of valence electrons (Zt) according to the lawMt=(Zt−22)μB. The calculated values of the minority-spin energy gap (Eg) and of the half-metallic gap (EHM) for the explored materials show that they are promising compounds for spintronic applications.

Cu12@Au30Ag12: a magnetic pentakis icosidodecahedron molecule with core-shell configuration.

A 54-atom trimetallic core-shell Cu12@Au30Ag12 molecule has been identified by using first-principles calculations. This molecule with Ih symmetry consists of an icosahedral 12-atom Cu core (Cu12) coated by a pentakis icosidodecahedral 42-atom Au-Ag shell (Au30Ag12) composed of an icosidodecahedral Au30 and an icosahedral Ag12. Both the molecular dynamics simulations and vibrational frequency analysis demonstrate the high stability of Cu12@Au30Ag12. The analyses for electronic properties indicate that there exists spd hybridization which is crucial to maintain the geometrical configuration of Cu12@Au30Ag12. Moreover, a total spin magnetic moment of Cu12@Au30Ag12 is found to be 4 µB, which chiefly arises from the 6s states of Au atoms. A new type of sugar gourd-like [Cu12@Au30Ag11]n nanowire is also proposed; the results demonstrate that the nanowire exhibits metallic and magnetic behaviors. The magnetic Cu12@Au30Ag12 molecule and [Cu12@Au30Ag11]n nanowire can be promising candidates of novel magnetic nanomaterials and nanodevices.

Mechanisms of Complete Dissociation of CO2 on Iron Clusters.

Dissociation of CO2 on iron clusters was studied by using semilocal density functional theory and basis sets of triple-zeta quality. Fe2 , Fe4 , and Fe16 clusters were selected as the representative host clusters. When searching for isomers of Fen CO2 , n=2, 4 and 16 corresponding to carbon dioxide attachment to the host clusters, its reduction to O and CO, and to the complete dissociation, it was found that the total spin magnetic moments of the lowest energy states of the isomers are often quenched with respect to those of initial reagents Fen +CO2 . Dissociation pathways of the Fe2 +CO2 , Fe4 +CO2 , and Fe16 +CO2 reactions contain several transition states separated by the local minima states; therefore, a natural question is where do the spin flips occur? Since lifetimes of magnetically excited states were shown to be of the order of 100 fs, the search for the CO2 dissociation pathways was performed under the assumption that magnetic deexcitation may occur at the intermediate local minima. Two dissociation pathways were obtained for each Fen +CO2 reaction using the gradient-based methods. It was found that the Fe2 +CO2 reaction is endothermic with respect to both reduction and complete dissociation of CO2 , whereas the Fe4 +CO2 and Fe16 +CO2 reactions are exothermic to both reduction and complete dissociation of carbon dioxide. The CO2 reduction was found to be more favorable than its complete dissociation in the Fe4 case.

Spin and orbital magnetism of exohedral fullerene doped with single transition metal atom (Sc-Ni): A relativistic density functional theory study

Relativistic density functional theory calculations have been implemented to study the structural configurations, electronic and magnetic properties of exohedral 3d transition metal atoms doping on C60 fullerene (TM-C60) by a full potential local orbital method. The calculated binding energies revealed that the TM-C60 molecules are energetically stable in all adsorption sites. We also found that the TM-doped exohedral C60 complexes are more reactive than pure C60 fullerene. The spin and orbital magnetic moments were also determined. We have indicated that in all of the five adsorption sites, exohedral TM-C60 molecules (except for Ni-C60) are magnetized. Our magnetic calculations show that the total spin magnetic moments of TM-C60 molecules mainly come from the TM atoms. We found that the spin magnetic moments of adsorbed TM atoms in exohedral doping C60 fullerene from Sc to Mn (HH adsorption site) and for Sc to Cr (HP and P adsorption sites) are greater than their free states. Our calculations suggest that exohedral doping 3d TM-C60 complexes can almost maintain spin magnetic moments. We have indicated that the magnetic properties of exohedral TM-C60 molecules change in the presence of spin–orbit coupling. Significant orbital contributions to magnetic moments are recognized in these configurations while the spin moments are unaffected. We found that Co in exohedral doping of C60 fullerene shows a robust orbital moment in all the five adsorption sites.

Identification of Ge═O Double Bonds in Planar MnGe3O and MnGe4O Clusters: Anion Photoelectron Spectroscopy and Ab Initio Calculations.

The structures, chemical bonding, and magnetic properties of MnGe3O-/0 and MnGe4O-/0 are investigated by photoelectron spectroscopy and ab initio calculations. The experimental vertical electron detachment energies of MnGe3O- and MnGe4O- are measured to be 2.06 ± 0.04 and 2.64 ± 0.04 eV, respectively. The structures of MnGe3O-/0 and MnGe4O-/0 can be viewed as evolved from quadrilateral MnGe3 or tetrahedral MnGe3. It is found that both MnGe3O- and MnGe3O have Cs symmetric planar structures with an O atom attached to quadrilateral MnGe3. The structure of MnGe4O- is nonplanar with an O atom and an additional Ge atom attached to tetrahedral MnGe3, while that of MnGe4O is planar with an O atom and an additional Ge atom attached to quadrilateral MnGe3. Chemical bonding analyses reveal the existence of Ge═O double bonds in MnGe3O and MnGe4O. Magnetic property analyses suggest that MnGe3O and MnGe4O are ferromagnetic with total spin magnetic moments of 5 μB.

Structure Optimization and Electronic Properties of Co2tix(X=Si, Ge) Heusler Alloys: A DFT Study

A theoretical study of structural, electronic, magnetic, mechanical and vibrational properties of Co-based heusler alloys, namely Co2TiX(X=Si,Ge); have been studied by the first principle calculations with the Generalized Gradient approximation(GGA) based on Density functional theory(DFT). The total spin magnetic moments per unit cell is 2µB, obeying the Slater-Pauling rule. The electronic band structure along the high symmetry points reveal that majority spin states have metallic character and minority spin states have a band gap at the Fermi level. There are no imaginary phonon mode which illustrate the dynamical stability. The Bulk modulus, young’s modulus, shear modulus, Pugh’s ratio, sound velocities, Debye temperature in accordance with the Voigt-Reuss-Hill approximation. The elastic constant results show that these alloys are mechanically stable.

Effect of doping titanium ions on semi‐conducting behavior, photovoltaic, and thermoelectric perovskite‐type oxides VSc 1−x Ti x O 3 : Ab‐inito study

Doping titanium's ions on perovskite-type oxides as VTixSc1−xO3; changes the semi-conducting behavior as well as magnetic, optical, and thermoelectric properties of VScO3 pervoskites. Doping titanium ions with different concentrations (x = 0.25, 0.5, 0.75, and 1) is investigated through the density functional theory (DFT) by the full potential linearized augmented plane wave (FP-LAPW) technique using GGA-mBJ potentials. All doped structures show semiconductor behavior in spin down channel, while the original structure VScO3 shows the same behavior in spin up channel. The values of energy band gap changes according the doped ions concentration Ti. The total spin magnetic moment increases as the concentration of Ti increases; the optical properties show a remarkable change during doping processes. The requirements for elastic-stability of crystal lattices are applied. All studied structures are mechanically stable, high value of the temperature of melting (Tm), and Debye temperature for VSc1−xTixO3 compounds is higher than 400°K, besides the high values of Young's modulus and bulk modulus all are implying the hardness of the perovskite. Calculated energy band structure by WIEN2k is utilized to calculate the transport coefficients by using the semi-classical Boltzmann transport theory depends on the constant relaxation time (τ) employed in the BoltzTraP package. Thermoelectric properties for all compounds are calculated and indicated that these compounds may be used in thermoelectric applications.

Investigation of structural, magnetic and electronic properties of CoMnSb superstructure: A DFT study

Using density functional theory (DFT) based electronic structure calculations, we have investigated the structural, magnetic and electronic properties of CoMnSb superstructure, to elucidate its physical properties and judge its suitability for device applications. We find that the fully optimized CoMnSb superstructure exhibits half metallicity in the bulk ordered structure with a half metallic gap of width ~0.22 eV and a total spin magnetic moment of 3.75 μB/f.u. (120 μB/unit cell). Furthermore, we have studied the role of intrinsic defects (anti-sites and atomic swaps) and strains (uniform and bi-axial) on the half metallic property of the superstructure. We find that the crystal structure of CoMnSb superstructure is stable against intrinsic defects and half metallicity is preserved for a few type of Co(Mn) atomic swap and anti-site defects. It is also observed that, half metallicity is retained for compressive uniform strain up to -3.0% and bi-axial strain up to -3.2%. As the width of the half metallic gap increases for isotropic strain and decreases for bi-axial strain, the former is a better choice for applications. We find that in a fully strained epitaxial thin film of CoMnSb superstructure deposited on GaAs(111) surface, half metallicity is expected to be retained, with the Ef lying within the gap. This condition is technologically more suitable compared to the unstrained condition, where the Ef lies at the top of the valence band.