Half-metallic Ferromagnets Research Articles

Inspecting the structural stability, magneto-opto-electronic, and transport characteristics of half-metallic ferromagnets double perovskite oxide (Sr2MoSbO6): A DFT study

The structural, elastic, mechanical, electronic, thermoelectric, and magnetic properties of the double perovskite Sr2MoSbO6 have investigated in this manuscript using Perdew-Burke-Ernzerhof Generalized Gradient Approximation (PBE-GGA) with an enhanced Trans Blaha modified Becke Johnson potential (TB-mBJ) approach. Through electro-magnetic and elastic exploration, we have determined that this compound is semiconductor, ferromagnetic, and brittle. Strong hybridisation between the Mo and Sr-d orbitals was seen in the Density of states (DOS) results, which, according to their relative quantities, supports the two states' ionic nature. The Mo atoms contribute significantly to the overall magnetic moment, which is 3.0 μB in total. The semiconducting nature of Sr2MoSbO6 is confirmed by the calculation of the overall electronic parameters. Calculations of thermodynamic parameters for temperature ranges of 0–1200 K and pressure ranges of roughly 0–30 GPa show good agreement between theoretical and experimental data. The DFT Boltzmann transport equations have been used to compute thermoelectric properties in relation to temperature and chemical potential. The p-type character of Sr2MoSbO6 is identified by positive values of the Seebeck coefficient. The power factor (PF), Seebeck coefficient (S), figure of merit (ZT), electrical conductivity, and lattice thermal conductivity were also calculated. It was discovered that this perovskite had a merit figure that was almost equal to one, a very high Seebeck coefficient, and strong electrical conductivity—all of which are consistent with its semiconductor nature. These findings suggest a substance with a great deal of promise for thermoelectrical uses. The results are taken into consideration for future experiments and may be future candidates for spintronics applications.

Triplet supercurrents in lateral Josephson junctions with a half-metallic ferromagnet

In the area of superconducting spintronics, spin-triplet supercurrents in half-metallic ferromagnets (HMFs) could yield dissipationless spin transport over large distances and high current density. Promising among the HMFs is the perovskite oxide La0.7Sr0.3MnO3 (LSMO), and recent studies in combination with the high-Tc superconductor YBa2Cu3O7, or the conventional superconductor NbTi, showed long-range effects. Here we focus on two issues that as yet have received less attention: the value of the critical current in the HMF in the limit of a very small electrode distance (20 nm) and the nature of the spin-triplet generator. We use lateral junctions shaped as a bar, square, and disk, and find high supercurrent densities of the order of 1011 A/m2, pointing to an efficient triplet generation mechanism. This is surprising in the sense that no magnetic inhomogeneity is purposely built in, as is done in conventional metal triplet junctions. Furthermore, from the magnetic field dependence of the critical current interference patterns, we find a uniform supercurrent distribution in bar-shaped devices, but one more constricted to the rim in disk devices, which is an expected consequence of the geometry. We also analyze the temperature dependence of the critical current and find the quadratic dependence that was predicted in the limit of small junction lengths. From studying the NbTi/LSMO interface with scanning electron transmission microscopy, we conclude that the magnetic inhomogeneity required for triplet generation resides in the LSMO layer adjacent to the interface. Published by the American Physical Society 2024

Half-metallic ferromagnetism and electronic structure of GeKX (X = Ca, Sr) alloys: a DFT-mBJ approach

Half-metallic ferromagnetism and electronic structure of GeKX (X = Ca, Sr) alloys: a DFT-mBJ approach

First-principle study origin of ferromagnetism in non-magnetic perovskite BaSnO3 doped with 2p-X (X=C, N)

In this study, our goal is to analyze the origin of magnetization in non magnetic cubic structure perovskite BaSnO3 doped with 2p-X (X=C, N) using the full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). For the exchange and correlation potential we have applied the generalized gradient approximation (GGA) and the GGA plus-modified Becke-Johnson potential (mBJ-GGA). The results show that BaSnO3 doped with C then with N and finally with C and N exhibit half-metallic ferromagnetism behavior with the integer magnetic moment of 1, 2 and 3 μB per cell respectively. The origin of the ferromagnetism that occurs within these compounds is mainly caused by the p-p hybridization between 2p-impurities and its neighboring oxygen atoms. These results allowed to conclude that doped perovskite could provide a new type of materials, called half-metallic for future spintronic devices.

V doped Orth-Ga2O3: Half-metallic ferromagnetism, large magnetic anisotropy energy and high Curie temperature

Half-metallic ferromagnets have attracted intense interest worldwide and are considered to be an important component of spintronics devices. In this paper, an unpredicted Ga2O3 phase (named as Orth-Ga2O3) with good mechanical, dynamic, and thermodynamic stability is proposed by employing the adaptive genetic algorithm (AGA) crystal structure prediction approach. Surprisingly, V-doped Orth-Ga2O3 (V@Orth-Ga2O3) exhibits a strong ferromagnetic (FM) half-metallicity with a magnetic moment of 2 μB per formula. A detailed analysis of the density of states shows that the FM half-metallicity originates from the double exchange interaction between V-3d and O-2p orbitals. Besides, V@Orth-Ga2O3 has a big magnetic anisotropy energy (MAE) of 0.36 meV, mainly due to the (dxy, dx2-y2) orbitals of the V atom. According to Monte Carlo simulations, the Curie temperature TC of V@Orth-Ga2O3 is 225 K. The effect of carrier concentration and strain on the ferromagnetic stability of V@Orth-Ga2O3 system is also investigated. These unique magnetic properties make V@Orth-Ga2O3 an extremely promising material in spintronic nanodevices.

Harnessing the half-metallicity and thermoelectric insights in Cs2AgMBr6 (M = V, Mn, Ni) double halide perovskites: A DFT study

Herein, we undertake a detailed exploration of the structural stability, magneto-electronic behavior, and thermoelectric properties of Cs₂AgMBr₆ (M = V, Mn, Ni) halide double perovskites using first-principles approach. The study commences with a meticulous assessment of both structural stability and thermodynamic properties employing various metrics. Energy minimization across different phases, utilizing the Birch-Murnaghan equation of state, confirms the ferromagnetic phase as energetically favoured, supported by Curie-Weiss constants of 98 K, 100 K, and 150 K for V, Mn, and Ni-based perovskites, respectively. Mechanical properties, including hardness, stiffness, ductility, and fracture strength, are derived from the simulated elastic constants, ensuring the mechanical stability of the materials. Electronic structure analysis, performed using the PBE-GGA and GGA + mBJ functionals, reveals that Cs₂AgMBr₆ compounds exhibit half-metallic ferromagnetism, with 100 % spin polarization at the Fermi level. Analysis of the partial density of states highlights the half-metallic ferromagnetic mechanism, confirming predominant ferromagnetic order through parameters such as the exchange splitting energy (Δx), p-d exchange interaction energy (Δx(p-d)), crystal-field energy (Ecrys), and exchange constants (N₀α and N₀β). The negative values of the exchange constants further validated the dominant ferromagnetic order in both s-d and p-d interactions, with unpaired electrons contributing magnetic moments of 2 μB for V, 4 μB for Mn, and 1 μB for Ni-based perovskites. Also, the Curie temperatures are calculated as 385 K, 747 K, and 204 K for V, Mn, and Ni-based perovskites. The overall findings, which reveal 100 % spin polarization and high zT values, underscore the significant potential of Cs₂AgMBr₆ halide perovskites for advancing spintronics and thermoelectric applications.

Atomic disorder and intrinsic anomalous Hall effect in a half-metallic ferromagnet Co2VAl

Half-metallic ferromagnets, conducting for one spin channel while insulating for the other, are highly desirable for spintronic applications due to 100 % spin polarization around the Fermi level. Cobalt-based half-metallic Heusler compounds have attracted enormous attention due to their large spin polarization and a high magnetic transition temperature. In the present study, we report the experimental and theoretical investigation of crystal structure and anomalous Hall effect (AHE) in half-metallic ferromagnet Co2VAl. The structural investigation of high-resolution synchrotron x-ray diffraction data reveals 10 % antisite disorder between V and Al atoms within the L21 ordered crystal structure. The scaling analysis of anomalous Hall data shows that the AHE in our system is mainly driven by the Berry curvature in the momentum space. The magnitude of experimental intrinsic anomalous Hall conductivity (AHC) due to the momentum space Berry curvature is about 44.67 ± 0.02 S/cm at 5 K, which is less than the theoretically calculated AHC for the ordered structure. Our theoretical calculations suggest that the lower AHC obtained for the present system is due to the reduced Berry curvature in the disordered case with negligible impact on half-metallicity of the system.

First-principles exploration of electronic, optical and magnetic features of Nb-doped BeTe for spintronic and optoelectronic devices

Herein, the magneto-electronic and optical features of Nb-doped Beryllium telluride (Be1−xNbxTe) have been computed using first-principles calculations. In electronic characteristics, the spin-polarized band dispersions and density of states explicate the half-metallic ferromagnetism at 6.25 % and 12.5 % doping concentration while metallic nature at 25 % doping. The total magnetic moments are recorded as 1.0, 2.0 and 4.0 μB for Be0.9375Nb0.0625Te, Be0.875Nb0.125Te and Be0.75Nb0.25Te, correspondingly. A tiny localized moment is generated at Be and Te site owing to TM-d with p-d hybridization. Optical parameters including refractive index n(ω), absorption coefficient α(ω), dielectric function ε(ω), optical conductivity σ(ω), extinction coefficient k(ω), and reflectivity R(ω) have been investigated. Be1−xNbxTe alloy has maximum value of α(ω) and minimum value of R(ω) within visible to UV zone. Overall outcomes imply that Be1−xNbxTe alloys seem to be the potential candidates for spintronics and optoelectronic devices.

Study of half-metallic ferromagnetism and transport properties of Cs2XI6 (X = transition metals) for spintronic and energy harvesting applications

The double perovskites (DPs) are an emerging applicant for spintronic devices. In the present paper, the ferromagnetism, Curie temperature, and transport characteristics of Cs2XI6 (X = Ta, W, Re, Os) are controlled by the 5d-electrons of transition metal ions. The optimization curves indicate the stability of ferromagnetic states because the energy released in ferromagnetic states is greater than in antiferromagnetic states. The formation energy and phonons dispersion calculations confirmed thermodynamic and dynamic stabilities, while the Goldsmith tolerance factor ensured structural stability. The Heisenberg model and polarization density findings ensure ferromagnetism at high temperatures and 100 % spin polarization. Furthermore, the analysis of the band structures and density of states shows that half-metallic ferromagnetism has a major contribution from 5d-X and 5p-I states. The hybridization, double exchange model, exchange constants, and crystal field energies are also reported for the comprehensive study of the origin of ferromagnetism. Finally, the Seebeck coefficients, electrical and thermal conductivities, and thermoelectric power are illustrated comprehensively. The significant values of the figure of merit make these materials potential candidates for energy harvesting applications.

Computational survey of optoelectronic properties and half-metallicity in ZnFeMnS: insight from first principles calculations

The electronic structure, optic and magnetic properties of the ZnFeMnS quaternary compound are studied on the basis of band-structure calculations, using full-potential linearized augmented plane wave (FPLAPW) method. The calculations are performed within the generalized gradient approximation (GGA). The calculated results indicate that ternary ZnMnS has an insulating character for the two directions of spin so, in its current form, it is inappropriate for spintronics devices. In contrary, Fe/Mn codoped ZnS is a half-metallic (HM) ferromagnet with a magnetic moment of 9 μB per formula unit. The integer magnetic moment of this compound indicates the stability of its half-metallic behavior. Consequently ZnFeMnS could be a promising dilute magnetic semiconductor for application in spintronic devices. Moreover, we have computed optical properties (absorption coefficient and reflectivity) of the two compounds, and have found a pronounced peak occurring at low energies for ZnFeMnS in all the optical curves due to transition metal (TM) impurity. The improvement of optical properties allows this compound to be used in manufacturing photovoltaic static converter or in display devices.

A DFT theoretical prediction of new half-metallic ferromagnetism, mechanical stability, optoelectronic and thermoelectric properties of ZnCrO3 perovskites for spintronic applications

ZnCrO3 perovskites structural stability, optoelectronic, mechanical, along with thermoelectric properties, have all been to be described by calculations based on density functional theory (DFT). To determine the exchange correlation potential, the well-known generalized gradient approximation (GGA) and integration of the mBJ potential were used. The perovskite shows that this is in a cubic structure with Fm3m symmetry. Additionally, to check the stability, cohesive energy, structural optimization, and mechanical stability were requirements. This perovskite was found to be brittle, and their mechanical stability enhanced by the elastic constants. The perovskite has a half-metallic character, as evidenced by the spin-polarized electronic band profile, the behavior of the dielectric constant, and absorption coefficient in the spin-up and down channels. In this article, we also looked at magnetism and the origin of the half-metallic gap. The unpaired electrons in the split d-orbitals of the M-sited elements in the crystal field are responsible for the half-metallic as well as magnetic characteristics. Excellent spin polarization at the Fermi level encourages perovskite's possible use in spintronic technologies. Lastly, we computed the thermoelectric parameters within a chemical potential at various temperatures (300 K, 600, 900 K) to explore the potential application in spin electronic devices. Our finding shows that the ZnCrO3 alloy is exceptionally promising for the next generation of spintronics and thermoelectric devices at room and high temperatures.

M3XSe4 (M = V, Cr; X = S, Te) monolayers: Intrinsic high-temperature ferromagnetic semiconductors and half metals

Creating low dimensional ferromagnetic (FM) semiconductors or half metals with strong FM orders is promising to meet the requirement for next-generation spintronics. However, most of the demonstrated FM semiconductors or half metals suffer from low Curie temperatures (TCs). Here, by first-principles calculations, we predict that the two-dimensional (2D) M3XSe4 (M = V, Cr; X = S, Te) monolayers are a type of intrinsic 2D ferromagnets with thermodynamical stability. Our results show that V3XSe4 (X = S, Te) monolayers are FM semiconductors with indirect bandgaps of 0.60 and 0.50 eV, respectively. Particularly, both structures are revealed to have high TCs of 387 and 770 K and suppress the application limit of room-temperature. In addition, Cr3XSe4 (X = S, Te) monolayers are FM half metals with 100% spin-polarized currents. Moreover, the electronic and magnetic properties of these M3XSe4 monolayers can be modulated by biaxial strains. V3TeSe4 monolayer can be tuned to be room temperature direct bandgap semiconductor under biaxial 1% tensile strain, and TC of V3SSe4 can be largely enhanced under compressive strains. Our results suggest that M3XSe4 monolayers are promising candidates for spintronic devices.

Half-metallic ferromagnetism in Fe-doped and Zn-vacancy defected ZnSe: First-principles investigation

The magnetic properties of defected ZnSe wurtzite systems were theoretically investigated using Density Functional Theory and Local Spin Density Approximation. From this first principal study, it was determined that pure ZnSe is a non-magnetic direct band gap semiconductor. Investigations show that adding the iron and the presence of a single Zn vacancy defect leads to the magnetization of ZnSe. The results of total energy calculations show that a ferromagnetic state is favorable when Zn is replaced with Fe. The ferromagnetic alignment in Fe-doped ZnSe wurtzite compound behaves in high-spin and half-metallic states.

Investigation of thermodynamical stability and generation of large half-metallic gap along with optical properties in N-doped YHfO3 (YHO) (Y = Ca, Sr, and Ba) perovskite materials by first principle calculations

Considerable energy gap (Eg) in insulating channel, high spin-filtering, significant mean free path, and high magnetic transition temperature (TC) escalate half-metallic (HM) ferromagnetic (FM) materials very enticing for spintronic applications. Herein, ab-initio calculations have been executed comprehensively to inquest the structural, thermodynamical, electronic, magnetic, and optical properties of pure as well as nitrogen (N)-doped YHfO3 (YHO) (Y = Ca/Sr/Ba) materials with one N atom added at one of the oxygen (O) site. First, the thermodynamical stability of both bulk and doped YHO systems has been examined by estimating the formation enthalpies (ΔHf) by Convex Hull analysis, which confirms the practical realization of these materials on experimental grounds. Moreover, mechanical stability of these systems is affirmed by estimating the necessary elastic constants and respective parameters. Strikingly, all doped systems possess complete (100%) splitting in spin↑ and spin↓ channels at Fermi level and depict HM FM character with significant Eg of 3.31, 3.49, and 3.24 eV in spin↓ channels for CaHO (CHO), SrHO (SHO), and BaHO (BHO) systems, respectively. It is also found that N 2p orbitals are totally responsible for the emergence of metatallicity and magnetic character in all these doped structures. Moreover, the ground state long range FM stability between two added N atoms in doped systems is affirmed by computing the difference of total energies of FM and anti-ferromagnetic (AFM) spin ordering (ΔE) along with estimated TC at different distances. Lastly, it is found that N-doped systems have a lower optical energy loss than pristine YHO systems in the incident photon energy range of 0-50 eV. Hence, the present study proposes that an unconventional doping approach with intrinsically non-magnetic element in a variety of YHO perovskite systems could be a useful method to alter their various physical properties and forecast their potential applications in the development of novel spintronic and optoelectronic devices.

Optoelectronic and structural properties of bulk cubic perovskite RbTaO3 and surface (0 0 1) for optoelectronic and spintronics applications

We used first-principles density functional theory (DFT) to study the optical, electronic, and structural properties of RbTaO3 cubic perovskite in both bulk and surface (0 0 1) forms. The RbTaO3 bulk system exhibited semiconducting behaviour with a band gap (Eg) of 2.20 eV. It showed weak reflectivity, excellent optical conductivity, and high absorption of incident energetic photons, indicating its potential for optoelectronic applications. For the surface (0 0 1), two RbO and TaO2 terminations were constructed. We calculate the atomic displacement (ΔZ) and surface energy (Esurf) for both terminations. The RbO- and TaO2-(0 0 1) terminated surfaces appeared half-metallic ferromagnetic (HMF) with a spin magnetic moment of integer value 1.00 μβ and fully spin polarization (SP) 100 %. The Eg for RbO- and TaO2-terminations were 2.60 eV and 2.30 eV, respectively, suggesting their potential for spintronics. We also analysed and compared the optical properties and atomic populations (Q) and their variation (ΔQ) for (0 0 1)-RbTaO3 terminations with the bulk system.

Study of Half Metallic Ferromagnetism and Thermoelectric Properties of the Spinels MgCo2(S/Se)4 for Spintronic and Energy Harvesting

Study of Half Metallic Ferromagnetism and Thermoelectric Properties of the Spinels MgCo2(S/Se)4 for Spintronic and Energy Harvesting

Thermodynamical stability and optoelectronic characteristics of Sr1-xCoxTe: A DFT study

Herein, the structural, electronic, magnetic and optical features of Sr1-xCoxTe alloys are investigated by using first-principles calculations. Stability of alloys is confirmed by the enthalpy of formation energy. The spin-dependent band structure (BS) and density of states (DOS) elucidate the half-metallic ferromagnetic (HMF) nature. For spin-down channel, Sr1-xCoxTe (x = 6.25 %, 12.5 %, 25 %) alloys have bandgap values of 1.30, 0.79 and 0.41 eV, respectively. The computed total magnetic moment for Sr1-xCoxTe (x = 6.25 %, 12.5 %, 25 %) are 3.00003, 5.99801, and 10.01265 μB, respectively. This robust magnetic ordering is primarily originated due to the incorporation of Co cations, which is further confirmed by spin magnetic density visualizer plots. Moreover, the optical features including dielectric constants, absorption, refraction and reflectivity of studied alloys have been analyzed within energy range 0–10 eV. Upon Co incorporation, the resulting alloys become optically active in the visible region of light. Overall, presented results suggest that Co-doped SrTe could be a potential material for optoelectronic and spintronic applications.

Point-contact spectroscopy of Leggett modes in superconducting compounds with unconventional pairing

Proximity-coupled nanostructures of conventional superconductors (SCs) and half-metallic ferromagnets (hmFs) are promising candidates as materials with unconventional superconductivity. The interrelated superposition of spin singlet-triplet and frequency even-odd superconducting condensates characterizes the superconducting state in such heterostructures. In a multi-band SC, the collective modes associated with the excitations of the relative phase between superconducting bands without perturbation of the Cooper pairs symmetry (Leggett modes) are allowed. In this report, we present the results of experimental investigations via the point-contact transport measurements of the Leggett-like collective excitations in the superconducting state of the nanocomposite of s-wave two-band superconductor MgB2 and half-metallic ferromagnet (La,Sr)MnO3. Two types of point contacts (PCs) have been used: the nanocomposite-nonmagnetic metal PCs and the nanocomposite–hmF PCs. The conductance equidistant peaks against the background of the gap structure were observed in both types of high-quality point junctions. Their distinctive feature was their period: two times shorter for the nanocomposite–hmF contacts compared to the nonmagnetic metal PCs. We attribute these spin-selective conductance periodic peaks to the relative phase Leggett’s excitations between “parents” MgB2 even-frequency singlet condensates and proximity-induced triplet superconducting condensates. The data obtained on the hmF PCs also demonstrate the features that may indicate a dynamic coupling between even-frequency condensates and odd-frequency gapless superconducting condensates.

The intrinsic ferromagnetic half-metals with high Curie temperature of tetragonal XCrS4 (X=Ti, Zr) monolayer

Two-dimensional intrinsic magnetic materials with a high Curie temperature (TC) and 100% spin-polarization are highly desirable for creating spintronic devices. In this work, the electronic structure and intrinsic magnetism of XCrS4 (X = Ti, Zr) monolayers are predicted by using first-principles calculations. XCrS4 (X = Ti, Zr) monolayer materials exhibit excellent dynamical, thermal, and dynamically stable stability and small binding energy. The band structures show that XCrS4 (X = Ti, Zr) monolayers are intrinsic ferromagnetic (FM) half-metals with wide half-metallic gaps. Monte Carlo simulations based on the Heisenberg model are used to estimate the Curie temperature (TC) of the TiCrS4 (73 K) and ZrCrS4 (216 K) monolayers. The magnetic performances can be significantly modulated by strain; the TiCrS4 monolayer can undergo FM to antiferromagnetic phase transition under certain uniaxial and biaxial strains. The results indicate that the intrinsic half-metals with higher TC and controllable magnetic properties make XCrS4 (X = Ti, Zr) monolayers enrich the application of nanoscale spintronic devices.

Half-metallic ferromagnetism with high critical temperatures in Substitutionally Doped Rare-Earth 2D Germanene

This work delves deep into the exploration of Rare-earth (RE) replacement doping germanene monolayers, where RE elements stand out for their fascinating electronic and magnetic nature derived from the elusive f-orbitals. Employing density functional theory (DFT) calculations, we unveil the electronic and magnetic characteristics of doped germanene systems. With its two-dimensional honeycomb structure, germanene holds immense promise for a wide range of applications within group IV materials. Through the discussion, we deeply uncover how the substitution of two specific concentrations of RE-atoms, namely La, Ce, Pr, Nd, Sm and Pm, transforms semi-metallic non magnetic germanene to half-metallic ferromagnets with remarkably high critical temperatures, when Hubbard correction is considered. These revelations not only deepen our comprehension of integrating f-orbitals into germanene but also open up exciting avenues for advancements in spintronic devices and beyond.