Spin-polarized Electronic Properties Research Articles

Efficiency improvement of spin-resolved ARPES experiments using Gaussian process regression

The experimental efficiency has been a central concern for time-consuming experiments. Spin- and angle-resolved photoemission spectroscopy (spin-resolved ARPES) is renowned for its inefficiency in spin-detection, despite its outstanding capability to directly determine the spin-polarized electronic properties of materials. Here, we investigate the potential enhancement of the efficiency of spin-resolved ARPES experiments through the integration of measurement informatics. We focus on a representative topological insulator Bi2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Bi}_{2}$$\\end{document}Te3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext {Te}_{3}$$\\end{document}, which has well-understood spin-polarized electronic states. We employ Gaussian process regression (GPR) to assess the accumulation of spin polarization information using an indicator known as the GPR score. Our analyses based on the GPR model suggest that the GPR score can serve as a stopping criterion for spin-resolved ARPES experiments. This criterion enables us to conduct efficient spin-resolved ARPES experiments, significantly reducing the time costs by 5-10 times, compared to empirical stopping criteria.

First-principle study of Mg-based rare earth spinels MgSm2Y4 (Y[dbnd]S, Se) for spintronic and thermoelectric devices

Mechanical, spin-polarized electronic, and transport characteristics of rare-earth-based MgSm2Y4 (YS, Se) spinels are investigated using first-principle calculations. In contrast to the anti-ferromagnetic and nonmagnetic states of MgSm2Y4 (YS, Se), the optimization study reveals that ferromagnetic states release more energy, and optimized lattice constants in ferromagnetic states are comparable to existing values. Phonon dispersion and formation energy are also calculated to confirm the dynamical stability stability. The ductile character is confirmed by investigating the Poisson's and Pugh ratios, and the values of other elastic parameters show their importance for the manufacturing of devices. Heisenberg model and the density of electron states at the Fermi level report the Curie temperature and the spin polarization. Spin-polarized electronic properties indicate half-metallic ferromagnetic because the spin-down reflects a semiconductor nature, whereas the metallic nature manifests the spin-up. The total magnetic moments are generated through hybridization of chalcogenide 2p-states and the Sm f-states. We found that the studied spinels may be used in thermoelectric devices by examining transport characteristics such as electronic and phononic thermal conductivity, Seebeck co-efficient, and figures of merit (ZT). Our results indicate that the ZT for MgSm2S4 is almost three times the ZT obtained for MgSm2Se4.

Exquisite control of electronic and spintronic properties on highly porous Covalent Organic Frameworks (COFs): transition metal intercalation in bilayers

Two-dimensional covalent organic frameworks (2D COFs) are crystalline organic porous materials stacked in a layered fashion. In general, these materials have excellent structural tunability, which can be achieved through the various tools of organic synthesis. Their layered and porous nature makes them attractive candidates for electronics, optoelectronics, and catalysis. However, their application is still limited due to relatively poor π-delocalization and practical applications require controlling and tuning their electronic structure. In this paper, using hybrid density functional theory, we computationally explore a novel 2D COF architecture, consisting of only two crystalline atomic layers made of benzene, boroxine, and triazine rings. We study the intercalation of first-row transition metals in the bilayer to enhance and fine-tune their electronic and magnetic behavior. This resulted in the development of one pristine bilayer, 63 intercalated bilayers, and one trilayer 2D COF. We found that the concentration and position of transition metals in the structure can drastically change the 2D COFs’ electronic, magnetic, and spintronic features. Based on their spin-polarized electronic properties, these transition metal-intercalated 2D COFs have potential applications as water splitting catalysts, direct semiconductors in the visible range, half metals, half semiconductors, and bipolar magnetic semiconductors.

Theoretical study on spintronic and optical property prediction of doped magnetic Borophene

Two dimensional materials are attracting new research for optoelectronics and spintronics due to their unique physical properties. A wide range of emerging spintronic devices are achieved from parent and doped two dimensional materials. First-principles electronic structure calculations of a two- dimensional monolayer of borophene in its P6/mmm form is explored in this study. The electronic, magnetic, and optical properties of doped borophene are analyzed for doping with lithium, sodium, and magnesium. Density functional theory calculations advocate their good dynamical and thermal stability. Spin-polarized electronic properties of these materials are observed to be useful for predicting new spintronic materials. Additionally optical analysis exhibits the absorption peaks in monolayers along the in-plane direction. These properties of doped magnetic borophene suggest the material to be a suitable candidate for designing optoelectronic devices. The most competent spintronic material among three different doped borophenes is lithium doping that can imply a promising avenue for the fast-growing electronics industry.

Spin-polarized electronic properties of naphthylene-based carbon nanostructures.

The 2D naphthylene-β structure is a theoretically proposed sp2 nanocarbon allotrope based on the assembly of naphthalene-based molecular building blocks, which features metallic properties. We report that 2D naphthylene-β structures host a spin-polarized configuration which turns the system into a semiconductor. We analyze this electronic state in terms of the bipartition of the lattice. In addition, we study the electronic properties of nanotubes obtained from the rolling up of 2D naphthylene-β. We show that they inherit the properties of the parent 2D nanostructure, such as the emergence of spin-polarized configurations. We further rationalize the results in terms of a zone-folding scheme. We also show that the electronic properties can be modulated using an external transverse electric field, including a semiconducting-to-metallic transition for sufficiently large field strength.

Enhanced thermoelectric efficiency in armchair silicene nanoribbons decorated by Mn

In this study, we use density functional theory to investigate the structural stability as well as the magnetic and thermoelectric properties of Mn-passivated armchair silicene nanoribbons (Mn-ASiNRs). All structures considered in this study were thermodynamically stable, and existed in ferromagnetic ground states with a Curie temperature greater than 400 K. The Mn-ASiNRs showed spin-polarized electronic properties that were tunable with respect to their width (N). Mn-ASiNRs with N = 4, 5, and 7 (4-, 5- and 7-Mn-ASiNRs) were semiconducting, while 6-Mn-ASiNR was half-metallic and 8-Mn-ASiNR was metallic. We simulated N-Mn-ASiNR-based devices to evaluate their thermoelectric properties, and observed a high-spin Seebeck coefficient (SS) of 1800 μV/K at μ=0 and a charge Seebeck coefficient (SC) of 1350 μV/K at μ=−0.17 eV for 4-Mn-ASiNRs. We obtained significantly enhanced charge and spin thermoelectric figures of merit (ZCT and ZST) compared with those of pristine nanoribbons (H-ASiNRs) that had maximum values of 25 and 18 at room temperature for 4- and 7-Mn-ASiNRs, respectively. ZCT and ZST further improved to values of 150 and 190, respectively, at temperatures lower than 100 K owing to a rapid increase in SC and SS, and exhibited decreased thermal conductance (Kt). Moreover, we showed that a thermally driven spin current with a negligibly small charge current can be generated by our devices. The results of this theoretical study indicate that Mn-ASiNR can be used to develop effective thermoelectric energy conversion devices.

Investigation of structural, electronic, elastic, magnetic and thermodynamic properties of antiperovskites XCRh3 (X = Cd, Ta, W, Re, Os, Ir, Pt, Au, Hg, Ce, Pr, Nd, Pm, Sm, Eu, Tb)

Antiperovskites have gained huge interest due to their distinctive physical, chemical, and thermodynamic properties. They are electronically inverted perovskites that turned out to be a growing class of versatile materials, providing a dynamic and effective research field to materials scientists. The present work is designated to study significant physical properties of novel antiperovskites XCRh3 (X = Cd, Ta, W, Re, Os, Ir, Pt, Au, Hg, Ce, Pr, Nd, Pm, Sm, Eu, Tb) using density functional theory based first-principles approach. This study includes the investigation of the structural, electronic, elastic, magnetic, and thermodynamic properties of the presented antiperovskites. Both the paramagnetic and ferromagnetic phases have been considered for computing the formation energy of compounds to elaborate the structural and mechanical stability. The spin-polarized electronic properties of ferromagnetic stable compounds demonstrated metallic features at the Fermi level in both spin versions. The mechanical parameters related to macroscopic properties, i.e., Young's modulus, Bulk modulus, shear modulus, tetragonal shear modulus, Poisson's ratio, Pugh's ratio, Cauchy's pressure, Zener anisotropic factor, lubrication factor, and compressibility factor have also been computed. The quasi-harmonic Debye model has been employed to analyze various important thermodynamic properties under a broad range of pressure (0–50 GPa) and temperature (0–1400 K).

First-principles calculations to investigate structural, mechanical, electronic, magnetic and thermoelectric properties of Ba2CaMO6 (M=Re, Os) cubic double perovskites

Structural, mechanical, electronic, magnetic and thermoelectric characteristics of Ba2CaMO6 (M = Re, Os) double perovskites have been calculated using first-principle based full-potential linearized augmented plane wave (FP-LAPW) approach. Optimized ground-state lattice constants of the compounds are in fair resemblance with the respective available experimentally investigated data. Calculated elastic constants and moduli show mechanical stability, anisotropy, ductility and significant stiffness. Computed spin-polarized electronic properties with a diversity of exchange-correlation potential schemes have revealed their half-metallic nature. Estimated spin magnetic moments indicate their ferromagnetic nature with major contributions from the 5d state of transition elements Re and Os. The present study has projected both the perovskite compounds as prospective magnetic materials for a variety of half-metallic, ferromagnetic and spintronic applications. Calculated thermoelectric parameters have predicted their scope of thermoelectric applications in high temperature waste heat management.

Penta-Hexa-Graphene Nanoribbons: Intrinsic Magnetism and Edge Effect Induce Spin-Gapless Semiconducting and Half-Metallic Properties.

Two-dimensional materials with intrinsic long-range ordered magnetic moments have drawn a lot of attention. However, for practical applications, whether or not the magnetism is stable in their nanostructures has not been revealed. Here, based on the recently proposed magnetic penta-hexa-graphene, we study the electronic and magnetic properties of its nanoribbons (named PHGNRs). The results show that the PHGNRs have intrinsic robust magnetic moments that are different from zigzag graphene nanoribbons, where the magnetic moments caused by the edge effect are vulnerable. Moreover, the magnetic ground states, namely, ferromagnetic (FM) or antiferromagnetic (AFM), can be transformed by changing the width of PHGNRs. Most interestingly, under the FM ground state, the spin-polarized electronic properties reveal that the zigzag PHGNRs transform from spin-gapless semiconductors (SGSs) to half-metals, as the width of nanoribbons increases, while all the armchair PHGNRs are magnetic semiconductors. Furthermore, by considering different edge effects caused by the residual carbon atoms on the edges, the PHGNRs can further derive different types of SGSs, as well as half-metals. Our work suggests that the PHGNRs possessing intrinsic robust magnetic moments have potential applications in the field of spintronic devices.

Formation Energetics, Electronic Structure and Ferromagnetic Properties of C-, Si- and Ge-Doped Zinc Blende Cadmium Chalcogenides

In the present study, we have investigated the structural, energetic, electronic and magnetic properties of zinc blende cadmium chalcogenides CdCh (Ch = S, Se and Te) compounds doped with group 14 elements, M = C, Si and Ge, at the anion site, using spin-polarized density functional theory calculations. The stability of all the M-doped CdCh systems is examined by computing formation energy at selected values of the chemical potentials for the atomic species participating in substitutional doping. In addition, the thermal stability of pristine as well as doped systems is examined by employing ab-initio molecular dynamics simulations. The effect of structural relaxation on the bond lengths together with the magnetic moments of M-doped CdCh systems indicate that the difference in the electronegativities and atomic radii of the dopant and chalcogen atoms determines the magnetic behaviour in these materials. Our results reveal that the spin-polarized electronic properties in M-doped cadmium chalcogenides are mainly caused by the occupancy of p orbitals of the dopant tetrels. Asymmetric insulating and p-type nature in spin-up and spin-down channels, respectively, is obtained in all M-doped CdS and CdSe compounds and Ge-doped CdTe, which results in a total magnetic moment of 2.0 μB per supercell. The magnetic moments of silicon and carbon doped CdTe, on the other hand, are found to be 1.88 μB and 0.07 μB, respectively, where the vanishing magnetic moments is caused by decreasing assymteric distribution of electrons in the spin-up and spin-down states of Si-3p and C-2p states.

Study of Vanadium Difluoride AVF3 (A = Na, K, Rb) for Optoelectronic and Thermoelectric Device Applications via Ab Initio Calculations

The cubic vanadium difluoride AVF3 (A = Na, K, Rb) are investigated as potential candidates for magnetic, optical, and thermoelectric device applications using density functional theory (DFT). The spin-polarized electronic properties are calculated for observing the exchange splitting to elucidate the ferromagnetic (FM) nature, which further confirmed by computed Jahn-Teller (ΔJT), direct Δx(d), and indirect exchange Δx(pd) energies. Owing to the strong hybridization mediated between V-3d and F-2p states, the V magnetic moment is found decreasing and fractional magnetic moments at A and F sites appear. The optoelectronic device applications are revealed by computing significant optical parameters. Boltzmann transport theory is utilized for computing thermoelectric applications using BoltzTraP, and various fundamental parameters are extracted and elaborated for understanding the thermoelectric natures of the studied perovskites.

DFT Investigations of Structural, Magnetic, Electronic, and Optical Properties of CsEuCl3

Full potential linearized augmented plane wave method was used to calculate structural, electronic, magnetic, and optical properties of CsEuCl3 within the framework of density functional theory. The ground state stability of CsEuCl3 was tested among non-magnetic, ferromagnetic, and anti-ferromagnetic phases. It was found that CsEuCl3 is stable in ferromagnetic phase. The computed ground state structural parameters in stability phase show excellent agreement with the available literature. The spin-polarized electronic properties reveal that CsEuCl3 is a direct band gap semiconductor in spin-up channel and large indirect band semiconductor in spin-down states. So, the overall nature of CsEuCl3 is semiconductor. The computed magnetic properties show that the main contribution toward ferromagnetic nature of studied compound is from the Eu atom. The calculated optical properties indicated the usefulness of CsEuCl3 in devices working in visible and ultraviolet regions of electromagnetic spectrum.

Study of Structural, Electronic, and Magnetic Properties of Cubic Lanthanide Based on Oxide Perovskite-Type NdGaO3

Based on the density functional theory (DFT), the full-potential linearized augmented plane wave with local orbital (FP-L/APW+lo) technique is now employed in this approach to understand the structural, electronic, and magnetic properties of simple cubic oxide perovskite NdGaO3 compound. In all this investigation, the exchange-correlation (XC) energy is selected in the framework of spin-polarized generalized gradient approximation (spin-GGA). The structural analysis unveils that the ferromagnetic (FM) phase is the stable ground state of the cubic NdGaO3 compound, where the equilibrium lattice parameters (lattice constant (a0), bulk modulus (B0), and its first pressure derivative (B′)) are determined in both FM and paramagnetic (PM) phases. The spin-polarized electronic properties (band structure and density of states) of the cubic NdGaO3 oxide perovskite are studied under the platform of equilibrium lattice parameters; this investigation demonstrates the half-metallic behavior of the studied cubic NdGaO3 compound because the spin-up case displays the metallic nature, whereas the semiconducting character is observed in spin-down case. The magnetic properties reveal that the total magnetic moment of the cubic NdGaO3 compound is equal to 3 μB and its contribution is mostly generated by Nd atoms, whereas feeble local magnetic moments are installed in non-magnetic Ga and O sites. Through the electronic and magnetic results, we conclude that the cubic perovskite NdGaO3 compound is classified as a half-metallic ferromagnetic material.

Rhombohedral Lanthanum Manganite: A New Class of Dirac Half-Metal with Promising Potential in Spintronics.

Dirac half-metals have drawn great scientific interests in spintronics because of their outstanding physical properties such as the large spin polarization and massless Dirac fermions. By using first-principles calculations, we investigate the perovskite-type lanthanum manganite (LaMnO3) as a novel Dirac half-metal. Specifically, LaMnO3 displays multiple linear band crossings in the spin-up direction, while it has a large band gap (∼5 eV) in the spin-down orientation. The intriguing linear band dispersions guarantee the ultrafast electron transport and the significant band differences between spin up and down directions promise the realization of 100% spin-polarized current and the extremely low energy consumption. Such a spin-polarized Dirac material is rare among perovskite-type compounds. By adopting the mean-field theory, the estimated Curie temperature Tc is 438.4 K. Importantly, the LaMnO3 crystal has been experimentally realized 2 decades ago, which facilitates the future experimental validation. With the novel spin-polarized electronic properties and the high possibility of experimental fabrication, LaMnO3 is ideal for the spintronic application.

Effect of Grain Size on Magnetic Properties of ZnO Doped with Nickel Single Impurities

The purpose of our study is to find a suitable material to be used in spintronic applications and to find the relation between the parameters of deposition by spray pyrolysis technic (temperature, concentration of Ni doping) and the ferromagnetic properties (Curie temperature, magnetic moment). The nickel-doped zinc oxide, Zn.1−x.NixO (x = 0.01, 0.03, 0.05), and diluted magnetic semiconductors (DMSs) are synthesized by the spray pyrolysis technic. The results of The X-ray diffraction (XRD) of prepared substrates confirm the incorporation of the dopants into the ZnO lattice structure. The spin-polarized electronic properties has been found and was investigated in detail by using the density-functional theory (DFT), the local density approximation (LDA), and The Korringa–Kohn–Rostoker coherent potential approximation (KKR-CPA). As result, nickel doping brings up a half-metallic appearance due to the hybridization between the 3d state of Nickel impurities and the oxygen 2p state. The mechanism of the interatomic exchange has been explained as being a p-d double exchange.

A theoretical investigation on the possible improvement of spin-filter effects by an electric field for a zigzag graphene nanoribbon with a line defect

The spin-polarized electronic properties for a zigzag-edge graphene nanoribbon (ZGNR) with an extended line defect are investigated, particularly focusing on controlling the effects of an external transverse electric field (Eext). An ab initio scanning tunneling microscope image for the defective ZGNR is also predicted. Results show that such a ZGNR can exhibit a strong spin polarization and ferromagnetic state, and the spin-filter effect can be significantly tuned and improved by the Eext. The spin-filter efficiency for our proposed device is predicted to be able to reach up to 60–81% in a large bias range of 0–0.6V at Eext=3.0V/nm. Mechanisms for such results and the experimental feasibility for the device are suggested. These findings suggest a new possibility for developing nanometer-scale all-carbon spintronic devices.

Spin-polarized electronic properties of NiHe0.25 under pressure

This paper studies the effects of He atom on the spin-polarized electronic properties of nickel under pressures using ab initio pseudopotential plan-wave method. Under high pressures, the compound of NiHe0.25 can exist and heliumbubble can not create in Ni. A pressure-induced ferromagnetic to paramagnetic phase transition has been predicted in NiHe0.25 at about 218 GPa. It is found that under pressures, the magnetic property of Ni atoms is more strongly affected by He atom than by H atom and that the behaviour of He atom in Ni are completely different from that of H atom, like the bonding characteristics and the electron transfer.

Magnetic trends in Mn n nanoclusters effects of uniform relaxations on the magnetic properties

We have computed minimum energy magnetic structure configurations of Mn nanoclusters ranging from 10 to 55 atoms in size. Spin-polarized electronic properties are calculated by solving an spd tight-binding Hubbard like Hamiltonian in the unrestricted Hartree–Fock approximation by using a bulk-like parametrization. Uniform expansions and contractions are done to follow the dependence of magnetization on interatomic distance. The obtained results allow us to infer that close shell icosahedral structures are competitive with bcc-like ones for N=13, 19, 32, and 42, whereas for other N values the bcc (with and without central atom) are the ones with lowest electronic energy reproducing the general experimental behaviour.