Half-metallic Materials Research Articles

Investigations on full-Heusler alloys Mn2TaAl and Mn2WAl for spintronic and thermoelectric applications

Half-metallic materials are widely used as spintronic devices such as electrodes, magnetic tunnelling junction and giant magnetoresistance etc. In this work, we have systematically investigated the structural stability, Gilbert damping, electronic structure and magnetism together with exchange interactions and Curie temperatures for Mn2TaAl and Mn2WAl alloys. Initially, we estimate their structural stability and offer possible phase synthesis. Subsequently, the Gilbert damping parameters calculated by the linear response theory are used to assess their response speed as spintronic materials. Furthermore, the Mn2TaAl and Mn2WAl are predicted to be half-metallic and nearly half-metallic ferrimagnets, their total magnetic moments obey the Mt=Zt-18 rule. Accordingly, their Curie temperatures for Mn2TaAl and Mn2WAl are also evaluated by the mean-field approximation. Finally, their thermodynamic parameters within 0∼600 K and thermoelectric properties within 200∼900 K are discussed. Overall, our research for Mn2TaAl and Mn2WAl alloys might provide some valuable clues for their application in spintronic devices.

Autonomous search for half-metallic materials with B2 structure

Autonomous search for half-metallic materials with B2 structure

A Density Functional Theory Study of the Physico-Chemical Properties of Alkali Metal Titanate Perovskites for Solar Cell Applications.

The urgent need to shift from non-renewable to renewable energy sources has caused widespread interest in photovoltaic technologies that allow us to harness readily available and sustainable solar energy. In the past decade, polymer solar cells (PSCs) and perovskite solar cells (Per-SCs) have gained attention owing to their low price and easy fabrication process. Charge transport layers (CTLs), transparent conductive electrodes (TCEs), and metallic top electrodes are important constituents of PSCs and Per-SCs, which affect the efficiency and stability of these cells. Owing to the disadvantages of current materials, including instability and high cost, the development of alternative materials has attracted significant attention. Owing to their more flexible physical and chemical characteristics, ternary oxides are considered to be appealing alternatives, where ATiO3 materials-a class of ternary perovskite oxides-have demonstrated considerable potential for applications in solar cells. Here, we have employed calculations based on the density functional theory to study the structural, optoelectronic, and magnetic properties of ATiO3 (A=Li, Na, K, Rb, and Cs) in different crystallographic phases to determine their potential as PSCs and Per-SCs materials. We have also determined thermal and elastic properties to evaluate their mechanical and thermal stability. Our calculations have revealed that KTiO3 and RbTiO3 possess similar electronic properties as half-metallic materials, while LiTiO3 and CsTiO3 are metallic. Semiconductor behavior with a direct band gap of 2.77 eV was observed for NaTiO3, and calculations of the optical and electronic properties predicted that NaTiO3 is the most appropriate candidate to be employed as a charge transfer layer (CTL) and bottom transparent conducting electrode (TCE) in PSCs and Per-SCs, owing to its transparency and large bandgap, whereas NaTiO3 also provided superior elastic and thermal properties. Among the metallic and half-metallic ATiO3 compounds, CsTiO3 and KTiO3 exhibited the most appropriate features for the top electrode and additional absorbent in the active layer, respectively, to enhance the performance and stability of these cells.

The half-metallicity, thermoelectric and optoelectronic attributes of K2CeB’X6 (B’=Ag, Cu & X=Cl, Br) for spintronics and renewable energies: A spin-polarized DFT study

The distinctive electronic characteristics of half-metallic materials make them exceptional as they pave the way for innovations in spintronics and other magnetic fields. We predict the ferromagnetism in half-metallic K2CeB’X6 (B’ = Ag, Cu & X = Cl, Br) perovskite halides by employing the spin-polarized computations. The tolerance factor, formation energies and optimization plots favor the structural stability of all perovskites. The K2CeB’X6 (B’ = Ag, Cu & X = Cl, Br) are half-metallic with a direct band gap of 2.59 eV, 2.53eV and 1.05eV, respectively, in the spin-down state, while the spin-up exhibit metallic character. The magnetic behavior is confirmed by the magnetic moment values. Several parameters for optical response are computed, showing the absorption in the visible and high energy spectrum. The spin-polarized response in terms of thermoelectric characteristics shows outstanding results. We have achieved the highest ZT values in spin-dn channel, which is unity for K2CeAgCl6, K2CeAgBr6 and 0.98 for K2CeCuCl6 at 300K. These values are continued even at higher temperatures with no significant change. The half-metallic characteristics with excellent thermoelectric attributes in the spin-dn channel provide the evidence to utilize these perovskites for spintronics and green technologies.

Contribution to the study of the CoFeTi Asquaternary Heusler material's structural, electronic, and magnetic properties

By simulating the structural, electronic, and magnetic properties of the QuateryCoFeTiAs Heusler compound, we presented a theoretical investigation in this work The calculations were performed using the generalized gradient (GGA) approximation and the WIEN2k code's application of the augmented plane wave method (FP-LAPW)which is based on density functional formalism (DFT). The results are consistent with important theoretical calculations.Our results showed that this compound conforms with the (Slater-Pauling) Mtot = (ZT - 24) μB rule and is a half-metallic material.

Implementation of excellent spin-filtering effect in half-metallic electrode-based single-molecule optoelectronic devices

The application of half-metallic materials in single-molecule optoelectronic devices opens a promising way in advancing device performance and functionality, thus addressing a research question of significance. Here we propose a series of single-molecule devices with half-metallic FeN4-doped armchair graphene nanoribbon as electrodes and metalloporphyrin (MPr) molecules as photoresponsive materials for photon harvesting, which are driven by photogalvanic effects (PGEs). Through the quantum transport simulations, we systematically investigated the spin-polarized photocurrents under the linearly polarized light illumination in these devices. Since the exclusive opening only exists in the spin-up channel of the half-metallic nanoribbons, these devices can generate a large photocurrent in the spin-up direction whereas suppressing the spin-down photocurrent. Consequently, they exhibit an effective spin-filtering effect at numerous photon energies. Our study unveils the excellent spin-filtering effect achieved in single-molecule optoelectronic devices with half-metallic electrodes, showing instructive significance for the future design of new optoelectronic devices.

The structure, magnetism and mechanical properties of L21-type full-Heusler alloy Cr2ZrSi: A first-principles study

Heusler alloy is a widely studied spintronic material in recent years, which has played a huge role in the field of spintronic devices due to its high spin polarization and high Curie temperature. Using first-principles calculation to predict the basic properties of Heusler alloy can not only save experimental costs and time but also provide a reliable theoretical basis for experimental research. This study used a first-principles calculation to study the magnetic and mechanical properties of full-Heusler alloy Cr2ZrSi with an L21-type structure. The research results indicate that the alloy is a half-metallic ferromagnetic material with a theoretical value of 100% spin polarization. The magnetism mainly comes from the asymmetric spin contribution of d-orbital electrons of transition metal atoms and their hybridization. At the same time, this complex hybridization coupling process is also a possible reason for the half-metallic band gaps. In terms of mechanical properties, the Cr2ZrSi alloy exhibits good ductility and anisotropy, with a Debye temperature of 303.848K. Our theoretical research results provide more choices and theoretical basis for subsequent experimental research.

Magnetic quadratic nodal lines in half-metallic anode material TiF3: A first-principles study

It is anticipated that nodal line materials may demonstrate unique physical phenomena. The traditional nodal line materials have a linear energy distribution surrounding them. A recent prediction is that systems may similarly stabilize nodal lines with a quadratic or cubic energy dispersion. This work focuses on a half-metal anode material, TiF3, which has already been predicted to host stable ferromagnetism and half-metallicity under Li insertion. Using first-principles calculation, we predicted for the first time that TiF3, a ferromagnetic material, has completely spin-polarized quadratic nodal lines along the Γ-X path. The half-metallic state and the spin-polarized quadratic nodal lines are robust to uniform strains (from −3 to +3 %). TiF3 can be regarded as a promising platform for deepening our comprehension of magnetic quadratic nodal lines in half-metals.

Ab initio prediction of half-metallic and metallic ferromagnetism in ZnO:(Co,Cr) systems

Doping effects on the electronic and magnetic properties of Zn1−x (Co,Cr) x O systems are investigated within Local Spin Density Approximation and Hubbard U methods. Based on Density Functional Theory the spin-polarization band structures, density of states for investigated systems are calculated. Systematic analysis of the electronic properties shows that TM-doped ZnO has generated new energy levels in the vicinity of Fermi energy level. From first-principle calculations we obtained Cr-ZnO and Co-ZnO systems are metallic and half-metallic ferromagnetic materials, respectively. The obtained results for Cr-doped ZnO 128- and 192-atom supercell systems show magnetic properties with higher Curie temperature than room temperature. There are large local moments, ∼2.9 and ∼4.2 for Co and Cr dopants, respectively. Magnetic moments are related with two electron defects in the supercell structure and unpaired electrons of transition metal. The ferromagnetic and antiferromagnetic phases and the total energy are obtained for x = 2.08%, 3.125%, 4.16%, 6.25%, 8.3%, 12.5%, and 25% impurity concentrations for doped ZnO.

Exploring the structural, mechanical, magneto-electronic and thermophysical properties of f electron based XNpO3 perovskites (X = Na, Cs, Ca, Ra).

Here, we present systematic investigation of the structural and mechanical stability, electronic profile and thermophysical properties of f-electron based XNPO3 (X = Na, Cs, Ca, Ra) perovskites by first principles calculations. The structural optimization, tolerance factor criteria depicts the cubic structural stability of these alloys. Further, the stability of these materials is also determined by the cohesive and formation energy calculations along with mechanical stability criteria. The electronic structure is explored by calculating band structure and density of states which reveal the well-known half-metallic nature of the materials. Further, we have calculated different thermodynamic parameters including specific heat capacity, thermal expansion, Gruneisen parameter and their variation with temperature and pressure. The thermoelectric effectiveness of these materials is predicted in terms of Seebeck coefficient, electrical conductivity and power factor. All-inclusive we can say that calculated properties of these half-metallic materials extend their route in spintronics, thermoelectric and radioisotope generators device applications.

Tunable Colossal Anomalous Hall Conductivity in Half-Metallic Material Induced by d-Wave-Like Spin-Orbit Gap.

The anomalous Hall conductivity (AHC) in magnetic materials, resulting from inverted band topology, has emerged as a key adjustable function in spin-torque devices and advanced magnetic sensors. Among systems with near-half-metallicity and broken time-reversal symmetry, cobalt disulfide (CoS2) has proven to be a material capable of significantly enhancing its AHC. In this study, the AHC of CoS2 is empirically assessed by manipulating the chemical potential through Fe- (hole) and Ni- (electron) doping. The primary mechanism underlying the colossal AHC is identified through the application of density functional theory and tight-binding analyses. The main source of this substantial AHC is traced to four spin-polarized massive Dirac dispersions in the kz = 0 plane of the Brillouin zone, located slightly below the Fermi level. In Co0.95Fe0.05S2, the AHC, which is directly proportional to the momentum-space integral of the Berry curvature (BC), reached a record-breaking value of 2507 Ω-1cm-1. This is because the BCs of the four Dirac dispersions all exhibit the same sign, a consequence of the d-wave-like spin-orbit coupling among spin-polarized egorbitals.

New quaternary half-metallic materials CoZrFeZ (Z = As, Sb): A first-principle study

New quaternary half-metallic materials CoZrFeZ (Z = As, Sb): A first-principle study

Electronic structure and magnetothermal properties of two-dimensional ScCl.

Two-dimensional ferromagnetic materials with intrinsic half-metallic properties have strong application advantages in nanoscale spintronics. Herein, density functional theory calculations show that monolayer ScCl is a ferromagnetic metallic material when undoped (n = 0), and the transition from metal to half-metal occurs with the continuous doping of holes. On the contrary, as the concentration of doped electrons increases, the system will exhibit metallic characteristics, which is particularly evident from a variation in spin polarizability. Furthermore, we have discussed how doped carriers affect the shape of the Fermi surface and the Fermi velocity of electrons. Most importantly, Monte Carlo simulations show that the ScCl monolayer is particularly regulated by carrier concentration (n) and magnetic field (h). Additionally, trends in energy and magnetic exchange coupling in different magnetic configurations (AFM phase and FM phase) with different doping concentrations are presented. When n < -0.16, the material is not only a half-metallic material that easily flips the magnetic axis, but also proves to be a candidate ferromagnetic material that works stably at room temperature in terms of dynamic stability. In addition, the origin of magnetocrystalline anisotropy is analyzed, and the contribution of different orbitals to spin-orbit coupling is presented. Moreover, we note that when magnetic field is small (h < 1 T), the change in size has a significant effect on ferromagnetic phase transition. However, when the system size is large (size >15 nm), TC is less sensitive to magnetic field. In addition, hole doping and size effect will greatly affect the hC of the system, but when the hole doping exceeds the critical value (n = -0.16), its influence on the hysteresis loop is no longer obvious. These interesting magnetic phenomena and easily adjustable physical properties show us that monolayer ScCl will be a promising functional material.

First-principles prediction of two-dimensional NiI[formula omitted] monolayer with adsorbed metal atoms

Monolayer NiI3 is a new two-dimensional (2D) intrinsic ferromagnetic Dirac half-metal material, and has attracted widespread attention due to its high Curie temperature and large magnetic anisotropy. In this work, we use first-principles calculations to study the physical properties of 2D NiI3 monolayer with adatom Y (Y=Li, Al, Mg, Ga). Our calculations show that Mg transforms the NiI3 monolayer from a half-metal to a bipolar magnetic semiconductor with a direct bandgap. While, the Li-NiI3, Al-NiI3, and Ga-NiI3 systems exhibit the band properties of 2D half-metals. In addition, the compressive strain can significantly increase the Curie temperatures of monolayer Li-NiI3 and Ga-NiI3. Especially under 1.5% compressive strain, the Mg-NiI3 system transitions from the ferromagnetic state to the antiferromagnetic state. Our study shows that atomic adsorption can optimize the properties of monolayer NiI3, and provides a theoretical basis for the use of atom adsorbed NiI3 system in experimental and device applications.

Room-temperature ferromagnetism, half-metallicity and spin transport in monolayer CrSc2Te4-based magnetic tunnel junction devices.

The discovery of novel two-dimensional (2D) half-metallic materials with a robust ferromagnetic (FM) order and a high Curie temperature (Tc) is attractive for the advancement of next-generation spintronic devices. Here, we propose a monolayer with stable 2D intrinsic FM half-metallicity, i.e., the CrSc2Te4 monolayer, which was constructed by intercalating a monolayer of 1T-CrTe2-type sandwiched between two layers of 2H-ScTe2 monolayers. Our calculations reveal that it exhibits exceptional dynamical, thermal, and mechanical stabilities accompanied by a robust half-metallicity characterized by a wide bandgap of 1.02 eV and FM ordering with a high Tc of 326 K. Notably, these properties remain intact in almost the entire range of the biaxial strain from -5% to 5%. Furthermore, our investigations demonstrate excellent spin transport capabilities, including an outstanding spin-filtering effect, and a remarkably high tunneling magnetoresistance ratio peaking at 6087.07%. The remarkable magnetic features of the 2D CrSc2Te4 monolayer with room temperature FM, intrinsic half-metallicity, and 100% spin-polarization make it a promising candidate for the next-generation high-performance spintronic nanodevices as well as high-density magnetic recording and sensors.

Unlocking OER catalytic potential and chiral Fe3O4 film as a game-changer for electrochemical water oxidation pathway and by-product control

This work report a Fe3O4 film with inherent chiral structure that effectively promoted OER, owing to its CISS effect on spin aligning intertwined with the capability of half-metallic materials to facilitate the transfer of spin-aligned electrons.

Electronic and half-metallic behaviour of manganese doped SiC Zigzag nanotubes using density functional theory

Single walled SiC nanotubes have gain centre of attraction due to the unique behaviours and potential application in the field of optoelectronics devices, LED, storage materials, and Photovoltaic materials. Electronic and structural properties of intrinsic and Manganese (Mn) doped SiC Zigzag nanotubes verified using first principle calculations associated with Density functional theory (DFT). Band gap of SiC Zigzag nanotubes influenced the structural and optical properties which play a crucial role in semiconductor application and create new opportunities in optoelectronic components. Electronic band plot of intrinsic SiC Zigzag nanotubes indicates band gap increased with the increase diameter of the nanotubes. PDOS plot shows 2p orbitals and 3p orbitals has major contribution on mostly filled valence band and lowest filled conduction band region whereas 2 s and 3 s orbitals of C atom and Si atom has minor contribution. Band structure plot of Mn doped SiC Zigzag nanotube introduced an extra energy layer in conduction band and resulting decrease the band gap value and valence band and conduction band cross the Fermi energy level in DOS plot representing the half-metallic characteristics which has different potential applications specially in photovoltaic materials. Half-metallic materials have outstanding spin transport characteristics. Spin-polarized electrons can effectively have conducted by Sic Zigzag nanotubes that controlled transport of spins. These half-metallic properties are essential for spintronic materials where electron spin used for information storage and processing. PDOS plot of Mn doped SiC Zigzag nanotube indicate 2p and 3p states of C atom and Si atom has major contribution compared to the 2 s and 2p states of C atom and Si atom whereas 3d orbitals of dopant Mn atom has major contribution near Fermi level of both conduction and valence band. This study highlights the potential optoelectronic applications of Mn doped SiC Zigzag nanotubes.

Magnetic, pressure-dependent elastic, and band gap calculations of VCo2O4 oxide spinel via GGA, GGA+mBJ, and GGA+U

The basis of spintronics is the technology involving nano-sized devices whose spins are directed. Therefore, materials that provide magnetic and 100 % spin polarization are remarkable. The ferromagnetic phase of VCo2O4 has obtained the most stable. In the GGA approximation, the equilibrium lattice constant and magnetic moment values were 8.34 Å and 10.00 μB/f.u., respectively. The band gaps in the GGA and GGA + mBJ approximations were calculated as 1.262 eV and 4.847 eV. The band gap values for Coulomb interactions U = 1, 2, 3, and 4 eV were obtained as 1.268 eV, 1.273 eV, 1.279 eV, and 1.286 eV, respectively. The elastic calculations showed that VCo2O4 was mechanically stable and ductile. The Debye temperature was calculated as 565 K at 0 GPa pressure. As a result, VCo2O4 oxide spinel has been obtained as a true half-metallic ferromagnetic material and will be a very good alternative for spintronic applications.

Electronic, magnetic, half-Metallic, pressure-induced elastic and curie temperature predictions of Zr2RhTl Heusler alloy: DFT and EFT studies

ABSTRACT The DFT method investigated the total and partial magnetic moments, half-metallic characters, and pressure-dependent elastic properties of Zr2RhTl alloy. According to the ground state properties, the FM phase is more stable in energy than the AFM and NM phases. The Curie temperature value was obtained as 897.43 K with the help of the energy differences of the AFM and FM phases. The total magnetic moment of Zr2RhTl alloy was obtained as 2.00 µB/f.u. Partial magnetic moment values were obtained as 0.810, 0.506, 0.032, and 0.009 µB for Zr1, Zr2, Rh, and Tl atoms, respectively. All these total and partial magnetic moment values and Curie temperatures were supported by the Effective Field Theory (EFT) method. In addition, partial Curie temperatures of Zr2RhTl alloy were calculated by EFT separately for each element. The up-spins of Zr2RhTl alloy show metallic character in both the GGA and GGA + mBJ approximations, while the down-spins have band gaps of 0.698 and 0.699 eV, respectively. Electronic properties were also supported by GGA + U (U = 1, 2, 3 eV) interactions. Therefore, Zr2RhTl alloy is a true half-metallic ferromagnetic material. Zr2RhTl alloy was elastically stable, and the Debye temperature was calculated as 221.496 K at 0 GPa. All calculations obtained using two different methods (DFT and EFT) and two different approximations (GGA and GGA + mBJ) support each other. Therefore, Zr2RhTl alloy proved to be a very suitable material to be used as an alternative for spintronics.

DFT calculations for electronic and magnetic properties of full Heusler Fe2MnAs alloy in perfect and defect structures

First-principles calculations within the framework of the density functional theory were conducted using the FP-LAPW method to investigate the electronic and magnetic properties of the Full-Heusler Fe2MnAs alloy. The study encompassed the examination of its perfect structure as well as the variation of lattice constants around the ground state. The negative value of the calculated formation energy suggests that the alloy may form spontaneously. From a magnetic perspective, Fe2MnAs exhibit a ferromagnetic order. The alloy also shows a high spin-polarization that may be increased, transforming the alloy into a half-metal, with the contraction of the lattice constant. Furthermore, the investigation delved into the effect of point defect formation. The calculated formation energies for vacancies, antisite, and exchange defects suggest the likely occurrence of some of these defects within the Fe2MnAs compound. Significantly, certain defects contribute to the spin-polarization of the alloy, effectively rendering it a fully half-metallic material.