Spin-up States Research Articles

The effect of biaxial strain on the electronic properties, quantum capacitance and diffusion of Li adsorption on Sc2CO2 MXene

Searching for high-performance electrode materials is an urgent need for lithium-ion batteries (LIBs) and supercapacitors. The electronic properties, quantum capacitance and diffusion of Li adsorption on Sc2CO2 under biaxial strain are investigated by density functional theory. Twelve adsorption sites are considered. The most stable adsorption site is confirmed through adsorption energy. The adsorption of Li makes Sc2CO2-Li monolayer become the magnetic semiconductor, with the maximum bandgap of 1.84 eV at −2 % strain and 0.76 eV at +4 % strain for spin-up and spin-down states, respectively. The maximum theoretical capacity of Sc2CO2 monolayer is 190.26 mAhg−1. The most appropriate diffusion path for Li atom is confirmed by analyzing diffusion barriers and Sc2CO2-Li monolayer under −4 % strain is more suitable as an anode material for LIBs because of the minimum open circuit voltage (OCV) and diffusion barrier. The coexistence of biaxial strain and Li adsorption doesn't change the cathode electrode type of Sc2CO2 monolayer. Charge transfer in Sc2CO2-Li monolayer under strain is further analyzed.

Intermediates-induced CO2 reduction reaction activity at single-atom M-N2 (M = Fe, Co, Ni) sites.

Single-atom M-N2 (M = Fe, Co, and Ni) catalysts exhibit high activity for CO2 reduction reaction (CO2RR). However, the CO2RR mechanism and the origin of activity at the single-atom sites remain unclear, which hinders the development of single-atom M-N2 catalysts.Here, we reveal intermediates-induced CO2RR activity at the single-atom M-N2 sites by density functional theory calculations.At the M-N2 sites, the asymmetric *O*CO configuration tends to split into *CO and *OH intermediates.Intermediates become part of the active moiety to form M-(CO)N2 or M-(OH)N2 sites, which can optimize the adsorption of intermediates on the M sites.The limiting potentials along the optimal CO2RR pathway are -0.30, -0.54, and -0.28 V for Fe-(OH)N2, Co-(CO)N2, and Ni-(OH)N2 sites, more positive than those of Fe-N2 (-1.03 V), Co-N2 (-1.24 V) and Ni-N2 (-0.73 V) sites.The intermediate modification can shift the d-band center of the spin-up (minority) state downward by regulating the charge distribution at the M sites, leading to less charge accepted by the intermediates from the M sites.This work provides new insights into the understanding of the activity of single-atom M-N2 sites.

Edge passivation oxidation-enhanced spin caloritronics in zigzag blue phosphorus nanoribbons

In this study, the spin caloritronics of zigzag blue phosphorus nanoribbons (ZBPNRs) with edge hydrogenation and oxidation were studied using first-principles calculations and the non-equilibrium Green’s function method. Three different cases were considered: two edges of the ZBPNR were oxidized (2O-ZBPNR) and hydrogenated (2H-ZBPNR), one edge was oxidized, and the other was hydrogenated (HO-ZBPNR). Our results show that a perfect thermal spin filtering effect (SFE) and a negative differential thermoelectric resistance (NDTR) can be observed in structures with both 2O-ZBPNR and HO-ZBPNR, whereas these features were not found for 2H-ZBPNR. Furthermore, we confirmed that edge oxygen atoms in ZBPNRs offer different transport pathways for spin-up and spin-down states, leading to thermal SFE, and devices with oxygen-passivated ZBPNRs exhibited strong spin figures of merit (∼38) and large spin Seebeck coefficients (∼9 mV K−1).

Ab-initio Calculations of the Half-metallic Ferromagnetic New Variant Perovskites Li2CrO6 and Li2CuO6

The half-metallic calculations of new variant perovskites Li2CrO6 and Li2CuO6 were carried out by using WIEN2k computational code. First, the ferromagnetic (FM) and non-magnetic (NM) phases were compared, and FM phases were obtained energetically more stable. The equilibrium lattice constants were obtained as 7.63 Å and 7.66 Å for Li2CrO6 and Li2CuO6, respectively. Second, the electronic calculations were performed, and the semiconduction properties were seen in spin-up states while spin-down states showed metallic nature. The band gaps were obtained as 1.806 eV and 1.177 eV for Li2CrO6 and Li2CuO6, respectively. Since variant perovskites Li2CrO6 and Li2CuO6 showed 100% spin polarizations, these were obtained as true half-metallic ferromagnetic materials. Then the total magnetic moments were obtained as 4.00 μB/f.u., 5.00 μB/f.u. When both the electronic and magnetic properties of the compounds are examined, the variant perovskites Li2CrO6 and Li2CuO6 are suitable materials for spintronics applications.

The Spin-down Accretion Regime of Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124

The relatively high fluxes of the Galactic ultraluminous X-ray pulsar Swift J0243 allow a detailed study of its spin-down regime in the quiescent state for the first time. After the 2017 giant outburst, its spin frequency shows a linearly decreasing trend with some variations due to minor outbursts. The linear spin-down rate is ∼ −1.9 × 10−12 Hz s−1 during the period of lowest luminosity, from which one can infer a dipole field of ∼1.75 × 1013 G. The relation during the spin-down regime is complex, and is close to zero when the luminosity reaches both the high end (L 38 ∼ 0.3) and the lowest value (L 38 ∼ 0.03). The luminosity of zero torque is different for the giant outburst and other minor outbursts. This is likely due to different accretion flows for different types of outburst, as evidenced by the differences in the spectra and pulse profiles at a similar luminosity for different types of outburst (giant or not). The pulse profile changes from double peaks in the spin-up state to a single broad peak in the low spin-down regime, indicating the emission beam/region is larger in the low spin-down regime. These results show that accretion is still ongoing in the low spin-down regime, for which the neutron star is supposed to be in a propeller state.

Ferromagnetism in Defected TMD (MoX2, X = S, Se) Monolayer and Its Sustainability under O2, O3, and H2O Gas Exposure: DFT Study.

Spin-polarized density-functional theory (DFT) has been employed to study the effects of atmospheric gases on the electronic and magnetic properties of a defective transition-metal dichalcogenide (TMD) monolayer, MoX2 with X = S or Se. This study focuses on three single vacancies: (i) molybdenum "VMo"; (ii) chalcogenide "VX"; and (iii) di-chalcogenide "VX2". Five different samples of sizes ranging from 4 × 4 to 8 × 8 primitive cells (PCs) were considered in order to assess the effect of vacancy-vacancy interaction. The results showed that all defected samples were paramagnetic semiconductors, except in the case of VMo in MoSe2, which yielded a magnetic moment of 3.99 μB that was independent of the sample size. Moreover, the samples of MoSe2 with VMo and sizes of 4 × 4 and 5 × 5 PCs exhibited half-metallicity, where the spin-up state becomes conductive and is predominantly composed of dxy and dz2 orbital mixing attributed to Mo atoms located in the neighborhood of VMo. The requirement for the establishment of half-metallicity is confirmed to be the provision of ferromagnetic-coupling (FMC) interactions between localized magnetic moments (such as VMo). The critical distance for the existence of FMC is estimated to be dc≅ 16 Å, which allows small sample sizes in MoSe2 to exhibit half-metallicity while the FMC represents the ground state. The adsorption of atmospheric gases (H2O, O2, O3) can drastically change the electronic and magnetic properties, for instance, it can demolish the half-metallicity characteristics. Hence, the maintenance of half-metallicity requires keeping the samples isolated from the atmosphere. We benchmarked our theoretical results with the available data in the literature throughout our study. The conditions that govern the appearance/disappearance of half-metallicity are of great relevance for spintronic device applications.

Exploring ice sheet model sensitivity to ocean thermal forcing and basal sliding using the Community Ice Sheet Model (CISM)

Abstract. Multi-meter sea level rise (SLR) is thought to be possible within the next few centuries, with most of the uncertainty originating from the Antarctic land ice contribution. One source of uncertainty relates to the ice sheet model initialization. Since ice sheets have a long response time (compared to other Earth system components such as the atmosphere), ice sheet model initialization methods can have significant impacts on how the ice sheet responds to future forcings. To assess this, we generated 25 different ice sheet spin-ups, using the Community Ice Sheet Model (CISM) at a 4 km resolution. During each spin-up, we varied two key parameters known to impact the sensitivity of the ice sheet to future forcing: one related to the sensitivity of the ice shelf melt rate to ocean thermal forcing (TF) and the other related to the basal friction. The spin-ups all nudge toward observed thickness and enforce a no-advance calving criterion, such that all final spin-up states resemble observations but differ in their melt and friction parameter settings. Each spin-up was then forced with future ocean thermal forcings from 13 different CMIP6 models under the Shared Socioeconomic Pathway (SSP)5-8.5 emissions scenario and modern climatological surface mass balance data. Our results show that the effects of the ice sheet and ocean parameter settings used during the spin-up are capable of impacting multi-century future SLR predictions by as much as 2 m. By the end of this century, the effects of these choices are more modest, but still significant, with differences of up to 0.2 m of SLR. We have identified a combined ocean and ice parameter space that leads to widespread mass loss within 500 years (low friction and high melt rate sensitivity). To explore temperature thresholds, we also ran a synthetically forced CISM ensemble that is focused on the Amundsen region only. Given certain ocean and ice parameter choices, Amundsen mass loss can be triggered with thermal forcing anomalies between 1.5 and 2 ∘C relative to the spin-up. Our results emphasize the critical importance of considering ice sheet and ocean parameter choices during spin-up for SLR predictions and suggest the importance of including glacial isostatic adjustment in ice sheet simulations.

Imprinting Spatial Helicity Structure of Vector Vortex Beam on Spin Texture in Semiconductors

We present the transfer of the spatially variant polarization of topologically structured light to the spatial spin texture in a semiconductor quantum well. The electron spin texture, which is a circular pattern with repeating spin-up and spin-down states whose repetition rate is determined by the topological charge, is directly excited by a vector vortex beam with a spatial helicity structure. The generated spin texture efficiently evolves into a helical spin wave pattern owing to the spin-orbit effective magnetic fields in the persistent spin helix state by controlling the spatial wave number of the excited spin mode. By tuning the repetition length and azimuthal angle, we simultaneously generate helical spin waves with opposite phases by a single beam.

Pressure dependent electronic, spintronic, optical and mechanical properties of equiatomic quaternary Heusler alloys NbMnVAl and NbFeCrAl

The pressure dependent physical properties of Nb-based equiatomic quaternary Heusler alloys NbMnVAl and NbFeCrAl have been investigated using full-potential linearized augmented plane wave (FP-LAPW) method with exchange and correlation potentials of the PBEsol scheme. Half-metallic behavior in NbMnVAl (NbFeCrAl) with band gap of 0.32 (0.29) eV in spin-down (spin-up) state at ambient pressure is observed. The total magnetic moments are derived as 2.0 μΒ/f.u. for NbMnVAl and NbFeCrAl alloys, which reconciles with Slater-Pauling rule. Phonon frequencies are computed using Vienna Ab initio Simulation Package (VASP). The exchange interactions and Curie temperatures are determined using spin-polarized relativistic Korringa-Kohn-Rostoker (SPR-KKR) method. Moreover, the computations of mechanical properties revealed the stability and ductile nature of both compounds. The optical properties proved the applicability of these compounds in optoelectronic devices. Pressure dependent half-metallic properties are discussed to show spintronic applications of both the quaternary alloys.

Density polarization effect of spin-up and spin-down electrons on magnetosonic solitons in a dense plasma with oblique magnetic field

Nonlinear wave propagation of fast and slow magnetosonic waves is investigated in a magnetized quantum plasma with spin polarization effects of degenerate electrons. The multi-fluid quantum magnetohydrodynamic model is considered and two separate fluid dynamic equations for degenerate electrons i.e. spin-up and spin-down states (Pauli paramagnetism) with their different Fermi pressures. The ions are assumed to be classical and external magnetic field lies in a plane. The magnetization energy and current density of electrons due to the spin-1/2 effects are included in the momentum equation of the degenerate electrons and Maxwell equations, respectively. A Korteweg-de-Vries (KdV) equation is derived for nonlinear magnetosonic waves in a dense magnetized plasma with the inclusion of electron spin effects and oblique external magnetic field. The electron inertial effect (which causes wave dispersion) of both spin-up and spin-down state electrons is also included in the model. It is found that electron spin polarization density has significant effects on the phase speed and soliton structures (i.e. its width and amplitude) of fast (hump) and slow (dip) magnetosonic waves in a dense magnetized plasma. The present theoretical study along with the obtained numerical results may have possible applications towards many realistic astrophysical scenarios.

Amorphous As2S3 Doped with Transition Metals: An Ab Initio Study of Electronic Structure and Magnetic Properties.

Crystalline transition-metal chalcogenides are the focus of solid state research. At the same time, very little is known about amorphous chalcogenides doped with transition metals. To close this gap, we have studied, using first principle simulations, the effect of doping the typical chalcogenide glass As2S3 with transition metals (Mo, W and V). While the undoped glass is a semiconductor with a density functional theory gap of about 1 eV, doping results in the formation of a finite density of states (semiconductor-to-metal transformation) at the Fermi level accompanied by an appearance of magnetic properties, the magnetic character depending on the nature of the dopant. Whilst the magnetic response is mainly associated with d-orbitals of the transition metal dopants, partial densities of spin-up and spin-down states associated with arsenic and sulphur also become slightly asymmetric. Our results demonstrate that chalcogenide glasses doped with transition metals may become a technologically important material.

First principles study on electronic, magnetic and optical properties of Gd2NiMnO6

The double perovskite oxide materials have various applications in light absorber, solid oxide fuel cells, electrode materials for electrochemical energy devices, solid state thermoelectric devices, etc. The calculations of electronic, optical and magnetic properties of Gd2NiMnO6 (GNMO) double perovskite are aimed in the present work. GNMO crystallizes in monoclinic structure with P21/n (14) space group. Implementing first principles density functional theory, we have reported the spin-polarised electronic band structure, density of states (DOS), optical absorption property and magnetic moment of GNMO double perovskite. Furthermore, the effect of on-site d-d Coulomb interaction energy (Ueff) on the electronic and optical properties were investigated by applying a range of Hubbard parameters from 0 to 6 eV on Ni-3d and Mn-3d orbitals within the local spin density approximation (LSDA) and generalised gradient approximation (GGA). Interestingly, on applying Ueff in this range, band gap of GNMO enhanced progressively in both majority and minority spins and also for Ueff = 4 and 6 eV implemented on Ni-3d and Mn-3d orbits, respectively, we observe the band gap value 1.16 and 2.12 eV for the spin-up and spin-down states which is in good agreement with the previously reported experimental band gap value (1.5 eV). In this regard, the electronic structure and light absorption of GNMO have been analysed for Ueff = 4 and 6 eV implemented on Ni-3d and Mn-3d orbits, respectively. The calculations revealed suitable narrow band gap and large visible light absorption coefficient in GNMO, which are extremely desired for the high photovoltaic performance.

Magnetic and spin transport properties of a two-dimensional magnetic semiconductor kagome lattice Nb<sub>3</sub>Cl<sub>8</sub> monolayer

Two-dimensional semiconductor materials with intrinsic magnetism have great application prospects in realizing spintronic devices with low power consumption, small size and high efficiency. Some two-dimensional materials with special lattice structures, such as kagome lattice crystals, are favored by researchers because of their novel properties in magnetism and electronic properties. Recently, a new two-dimensional magnetic semiconductor material Nb<sub>3</sub>Cl<sub>8</sub> monolayer with kagome lattice structure was successfully prepared, which provides a new platform for exploring two-dimensional magnetic semiconductor devices with kagome structure. In this work, we study the electronic structure and magnetic anisotropy of Nb<sub>3</sub>Cl<sub>8</sub> monolayer. We also further construct its <i>p-n</i> junction diode and study its spin transport properties by using density functional theory combined with non-equilibrium Green's function method. The results show that the phonon spectrum of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer has no negative frequency, confirming its dynamic stability. The band gap of the spin-down state (1.157 eV) is significantly larger than that of the spin-up state (0.639 eV). The magnetic moment of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer is 0.997 μ<sub>B</sub>, and its easy magnetization axis is in the plane and along the <i>x</i> axis direction based on its energy of magnetic anisotropy. Nb atoms make the main contribution to the magnetic anisotropy. When the strain is applied, the band gap of the spin-down states will decrease, while the band gap of the spin-up state is monotonously decreased from the negative (compress) to positive (tensile) strain. As the strain variable goes from -6% to 6%, the contribution of Nb atoms to the total magnetic moment gradually increases. Moreover, strain causes the easy magnetization axis of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer to flip vertically from in-plane to out-plane. The designed <i>p-n</i> junction diode nanodevice based on Nb<sub>3</sub>Cl<sub>8</sub> monolayer exhibits an obvious rectification effect. In addition, the current in the spin-up state is larger than that in the spin-down state, exhibiting a spin-polarized transport behavior. Moreover, a negative differential resistance (NDR) phenomenon is also observed, which could be used in the NDR devices. These results demonstrate that the Nb<sub>3</sub>Cl<sub>8</sub> monolayer material has great potential application in the next generation of high-performance spintronic devices, and further experimental verification and exploration of this material and related two-dimensional materials are needed.

First-principle computation of some physical properties of half-Heusler compounds for possible thermoelectric applications.

Using the density functional theory (DFT) method, we investigate the properties of LaXSi (X = Pt, Pd) half-Heusler compounds. To ensure the stability of both compounds, we employed two criteria: the Birch-Murnaghan equation of state and the negative formation energy. The evaluation of elastic constants (ECs) plays a crucial role in determining the mechanical stability of both compounds. Specifically, we ensure that the conditions C11 - C12 > 0, C11 > 0, C11 + 2C12 > 0, and B > 0 are satisfied and exhibit mechanical anisotropy and ductility. The analysis of electronic properties clearly indicates that LaPtSi displays metallic behavior in both the spin-up and spin-down states. In the spin-up state of LaPdSi, a band gap is observed, which indicates its characteristic of being a half-metal. A comprehensive investigation of optical properties revealed that these compounds display notable absorption and optical conductivity at higher energy levels. Conversely, they exhibit transparency to incident photons at lower energy levels. Based on the findings, it can be concluded that these compounds are highly suitable for application in high-frequency UV devices. The thermoelectric properties clearly indicate that both materials exhibit high power factors, electrical conductivity, and figures of merit (ZT), suggesting their potential as exceptional thermoelectric materials. The simulations conducted in this study consider the effect of on-site Coulomb interactions by incorporating the Hubbard U term within the GGA + U. Our findings contribute valuable insights that can facilitate further experimental investigations and provide comprehensive validation.

Magnetic and spin transport properties of a two-dimensional magnetic semiconductor kagome lattice Nb<sub>3</sub>Cl<sub>8</sub> monolayer

Two-dimensional semiconductor materials with intrinsic magnetism have great application prospects in realizing spintronic devices with low power consumption, small size and high efficiency. Some two-dimensional materials with special lattice structures, such as kagome lattice crystals, are favored by researchers because of their novel properties in magnetism and electronic properties. Recently, a new two-dimensional magnetic semiconductor material Nb<sub>3</sub>Cl<sub>8</sub> monolayer with kagome lattice structure was successfully prepared, which provides a new platform for exploring two-dimensional magnetic semiconductor devices with kagome structure. In this work, we study the electronic structure and magnetic anisotropy of Nb<sub>3</sub>Cl<sub>8</sub> monolayer. We also further construct its <em>p-n</em> junction diode and study its spin transport properties by using density functional theory combined with non-equilibrium Green's function method. The results show that the phonon spectrum of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer has no negative frequency, confirming its dynamic stability. The band gap of the spin-down state (1.157 eV) is significantly larger than that of the spin-up state (0.639 eV). The magnetic moment of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer is 0.997 μ<sub>B</sub>, and its easy magnetization axis is in the plane and along the <em>x</em> axis direction based on its energy of magnetic anisotropy. Nb atoms make the main contribution to the magnetic anisotropy. When the strain is applied, the band gap of the spin-down states will decrease, while the band gap of the spin-up state is monotonously decreased from the negative (compress) to positive (tensile) strain. As the strain variable goes from -6% to 6%, the contribution of Nb atoms to the total magnetic moment gradually increases. Moreover, strain causes the easy magnetization axis of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer to flip vertically from in-plane to out-plane. The designed <em>p-n</em> junction diode nanodevice based on Nb<sub>3</sub>Cl<sub>8</sub> monolayer exhibits an obvious rectification effect. In addition, the current in the spin-up state is larger than that in the spin-down state, exhibiting a spin-polarized transport behavior. Moreover, a negative differential resistance (NDR) phenomenon is also observed, which could be used in the NDR devices. These results demonstrate that the Nb<sub>3</sub>Cl<sub>8</sub> monolayer material has great potential application in the next generation of high-performance spintronic devices, and further experimental verification and exploration of this material and related two-dimensional materials are needed.

Weyl nodal lines, Weyl points and the tunable quantum anomalous Hall effect in two-dimensional multiferroic metal oxynitride: Tl2NO2.

The investigation of two-dimensional (2D) multiferroic and topological quantum phases is a significant topic in current condensed matter physics. In this study, we discover quantum topological phases in the multiferroic material Tl2NO2. We observe that its ferroelectric (FE) phase displays a ferromagnetic ground state with magnetization favoring in-plane orientation. In the absence of spin-orbit coupling (SOC), a Weyl nodal loop around the Fermi level is evident, representing a 1D band crossing between spin-up and spin-down states. When spin-orbit coupling is taken into account, setting the magnetization in-plane, the Weyl nodal loop becomes gapped. Additionally, a pair of 2D Weyl nodes appear on the high-symmetry path, protected by a vertical mirror symmetry allowed by the magnetization. Remarkably, we prove that the Weyl nodes are situated at the topological phase transition between two quantum anomalous Hall (QAH) phases with opposite Chern numbers. Therefore, by adjusting the magnetization, it is possible to switch the propagation direction of chiral edge states. Furthermore, from its ferroelectric state to a paraelectric state, the time-reversal symmetry breaking nodal line is transformed into a Weyl point, achieving 100% spin polarization. Particularly, the Weyl points remain robust against SOC when the vertical mirror symmetry is preserved. Importantly, we also demonstrate that the Weyl point also represents the transition point where the QAH phase changes the sign of its Chern number. Overall, our study provides new insights into the study of multiferroic and topological phenomena in 2D materials and offers a potential avenue for controlling QAH phases.

Distinct ferrovalley characteristics of the Janus RuClX (X = F, Br) monolayer.

Two-dimensional ferrovalley materials should simultaneously possess three characteristics, that is, a Curie temperature beyond atmospheric temperature, perpendicular magnetic anisotropy, and large valley polarization for potential commercial applications. In this report, we predict two ferrovalley Janus RuClX (X = F, Br) monolayers by first-principles calculations and Monte Carlo simulations. The RuClF monolayer exhibited a valley-splitting energy as large as 194 meV, perpendicular magnetic anisotropy energy of 187 μeV per f.u., and Curie temperature of 320 K. Thus, spontaneous valley polarization at room temperature will be present in the RuClF monolayer, which is nonvolatile for spintronic and valleytronic devices. Although the valley-splitting energy of the RuClBr monolayer was as high as 226 meV with magnetic anisotropy energy of 1.852 meV per f.u., the magnetic anisotropy of the RuClBr monolayer was in-plane, and its Curie temperature was only 179 K. The orbital-resolved magnetic anisotropy energy revealed that the interaction between the occupied spin-up states of dyz and the unoccupied spin-down states of dz2 dominated the out-of-plane magnetic anisotropy in the RuClF monolayer, but the in-plane magnetic anisotropy of the RuClBr monolayer was mostly contributed by the coupling of the dxy and dx2-y2 orbitals. Interestingly, the valley polarizations in the Janus RuClF and RuClBr monolayers appeared in their valence band and conduction band, respectively. Thus, two anomalous valley Hall devices are proposed using the present Janus RuClF and RuClBr monolayers with hole and electron doping, respectively. This study provides interesting and alternative candidate materials for the development of valleytronic devices.

Novel germanene-arsenene and germanene-antimonene lateral heterostructures: interline-dependent electronic and magnetic properties.

Seamlessly stitching two-dimensional (2D) materials may lead to the emergence of novel properties triggered by the interactions at the interface. In this work, a series of 2D lateral heterostructures (LHSs), namely germanene-arsenene (Gem-As8-m) and germanene-antimonene (Gem-Sb8-m), are investigated using first-principles calculations. The results demonstrate a strong interline-dependence of the electronic and magnetic properties. Specifically, the LHS formation along an armchair line preserves the non-magnetic nature of the original materials. However, this is an efficient approach to open the electronic band gap of the germanene monolayer, where band gaps as large as 0.74 and 0.76 eV are induced for Ge2-As6 and Ge2-Sb6 LHSs, respectively. Meanwhile, magnetism may appear in the zigzag-LHSs depending on the chemical composition (m = 3, 4, 5, and 6 for germanene-arsenene and m = 2, 3, 4, 5, and 6 for germanene-antimonene), where total magnetic moments between 0.13 and 0.50 μB are obtained. Herein, magnetic properties are produced mainly by the spin-up state of Ge atoms at the interface, where a small contribution comes from As(Sb) atoms. Spin-resolved band structures show a multivalley profile in both the valence band and the conduction band with a topological insulator-like behavior, where the interface states are derived mainly from the interface Ge-pz state. The results introduce new 2D lateral heterostructures with novel electronic and magnetic properties to allow new functionalities, which could be further explored for optoelectronic and spintronic applications.

Ferromagnetic half-metal with high Curie temperature in Cr P nanoribbons: good material for spintronic applications.

In this work, the stability, and electronic, magnetic, and transport characteristics of chromium phosphorus nanoribbons (CrPNRs) have been investigated. The results, obtained from the non-equilibrium Green's function and density functional theory, indicate that the nanoribbon is stable in terms of binding energies as well as dynamically. The calculated electronic structure shows that this nanoribbon has an indirect band gap of about 1.67 eV for the spin-down channel and is metallic for the spin-up channel. The metallicity of the spin-up channel originates from the P-3p orbitals and the magnetic properties are due to the Cr-3d orbitals. The obtained transport properties indicate the value of the current for the spin-up state is about 50 μA. The negative differential resistance (NDR) phenomenon and also a 100% spin filtering effect are seen between voltages of 0.4 and 0.5 V. The results showed that CrPNRs have a high Curie temperature of more than 690 K, indicating that this nanoribbon is a useful ferromagnetic material for nanoelectronic devices and spintronic applications at ambient temperature.

Structural, dielectric, magnetic and magnetoelectric studies of (1-x) BaFe12O19-x BiFeO3 composites

The synthesis of multiferroic (1-x) BaFe12O19-x BiFeO3; (x = 0.05, 0.08, 0.10) composites was carried out with solid state reaction. The XRD data confirmed the formation of the composites with phases of both compounds. The low values of Rietveld refinement parameters along with modified lattice parameters of both hexaferrite and multiferroic phase reconfirmed the amalgamation of phases. FESEM with EDX were utilized for morphological study and elemental compositional analysis in the composites. The dielectric constant and tanδ both parameters showed typical low frequency dispersion. A mild anomaly in dielectric constant and tangent loss is quite noticeable near to magnetic transition temperature (TN) of BiFeO3 suggests the possible occurrence of magnetoelectric effect in prepared composite system. The fitting of AC conductivity data suggested the OLPT (overlapping large polaron tunneling) conduction process in the composite system. The saturation magnetization (Ms) showed a decreasing trend with increment of BiFeO3 content in composites owing to substituted Fe3+ ion in spin-up state. Coercivity (Hc) found in good agreement with magnetocrystalline anisotropy of hexaferrite phase. The improvements in magnetoelectric coupling coefficient of barium hexaferrite were clearly noticeable with the introduction of BiFeO3 phase owing to piezoelectric coefficient and magnetostriction of ferroelectric and ferrite phases respectively.