Showing papers on "Half-metal published in 2020"

Two-dimensional hexagonal chromium chalco-halides with large vertical piezoelectricity, high-temperature ferromagnetism, and high magnetic anisotropy.

Abstract: On the basis of density functional theory, we predicted that Janus CrTeI and CrSeBr monolayers possess highly energetic, dynamical, and mechanical stability Due to noncentral symmetry, the two monolayers exhibit vertical piezoelectricity with large piezoelectric coefficients d31 (1745 and 1716 pm V−1 for CrBSe and CrTeI, respectively), which are larger than those of most materials in existence Both systems are also ferromagnetic (FM) semiconductors, with Curie temperature (TC) higher than 550 K and large in-plane magnetic anisotropy energy Superexchange interactions are responsible for high-temperature FM order A semiconductor to half metal transition can be regulated by carrier doping, which can be carried out by gate voltages Doped systems still retain the same FM order as pristine ones; in particular, hole doping enhances exchange coupling, thereby increasing TC The combination of piezoelectricity, high TC, and controllable electronic structures and magnetic properties makes magnetic 2D Janus CrSeBr and CrTeI attractive materials for potential applications in nanoelectronics, electromechanics, and spintronics

First-principles computation of new series of quaternary Heusler alloys CoScCrZ (Z = Al, Ga, Ge, In): a study of structural, magnetic, elastic and thermal response for spintronic devices

Abstract: Various physical properties of CoScCrZ (Z = Al, Ga, Ge, In) Heusler alloys (HAs) are examined using full potential linearised augmented plane wave (FP-LAPW) method within framework of density funct...

Spin-valley polarized quantum anomalous Hall effect and a valley-controlled half-metal in bilayer graphene

Abstract: We investigate topological phases of bilayer graphene subject to antiferromagnetic exchange fields, interlayer bias, and light irradiation. We discover that at finite bias and light intensity the system transitions into a previously unknown spin-valley polarized quantum anomalous Hall (SVP-QAH) insulator state, for which the subsystem of one spin is a valley Hall topological insulator (TI) and that of the other spin is a QAH insulator. We assess the TI phases occurring in the system by analytically calculating the spin-valley-dependent Chern number and characterize them by considering edge states in a nanoribbon. We demonstrate that the SVP-QAH edge states lead to a unique spin rectification effect in a domain wall. Along the phase boundary, we observe a bulk half-metal state with Berry's phase of $2\ensuremath{\pi}$.

Prediction of MnSiTe 3 as an intrinsic layered half-metal

Abstract: Half-metallic materials allow electrons with one spin orientation to conduct through, while completely blocking electrons with the other spin orientation. Here we use a multiscale approach to predict that ${\mathrm{MnSiTe}}_{3}$ within the transition metal trichalcogenide (TMT) family is an intrinsic layered half-metal both in bulk form and at the ultrathin two-dimensional (2D) limit. We first use first-principles calculations to demonstrate that the system is a van der Waals crystal with weak interlayer coupling, allowing ready separation of a monolayer. Next we show that the half-metallicity of the bulk crystal is preserved also for a freestanding monolayer, with highly desirable ferromagnetic interlayer coupling. The ferromagnetic order of the monolayer is further shown to originate from the interplay of the exchange interaction and Ruderman-Kittel-Kasuya-Yosida coupling mediated by the itinerant carriers, while the singly spin-polarized and long-range nature of the latter is largely responsible for the unusually large next-next-nearest ferromagnetic coupling among the Mn ions. These findings, together with the latest developments surrounding ferromagnetism in 2D TMTs, may offer immense application potentials in nanomagnetic and spintronic devices.

Tunable two dimensional ferromagnetic topological half-metal CrO2 by electronic correction and spin direction

Abstract: Spintronics is one of the most promising information technologies now, especially for nontrivial topological Dirac half-metal, which exhibits extraordinary electronic band and transport properties. In this work, we propose that 1T-CrO2 nanosheet is mechanical stable, large spin-gap, and room temperature ferromagnetic Dirac half metal. It also exhibits a desirable giant magneto band structure effect, and when the spin direction is switched from in-plane to out-of-plane with a spin orbital coupling effect, it will exhibit nontrivial topological phase transition. The topological tunable electronic band property makes it a very promising two-dimensional nanosheet for spintronics.

Two-dimensional stable Mn based half metal and antiferromagnets promising for spintronics

Abstract: In this paper, we predict that the tetragonal MnSi and MnC0.5Si0.5 monolayers are mechanically stable metallic ferromagnetic materials. The thermal stability of the MnC0.5Si0.5 monolayer is verified by our ab initio molecular dynamics (AIMD) result at 300 K. Both MnSi and MnC0.5Si0.5 monolayers exhibit room temperature half-metallic properties, which is very promising for spintronic applications. Both monolayers exhibit large perpendicular magnetic anisotropy, which is desirable for maintaining magnetic order and for high density storage spintronics. A bilayer of the MnSi nanosheet has obviously enhanced thermal stability and exhibits antiferromagnetic metal properties. The Neel temperature could be effectively manipulated and improved by surface functionalization. In addition, monolayer and bilayer MnSi nanosheets exhibit nodal lines in the reciprocal space, and the nodal lines are robust against spin orbit coupling.

Anomalous Nernst effect in Co2MnSi thin films

Abstract: Separation of the anomalous Nernst and spin Seebeck voltages in bilayer devices is often problematic when both layers are metallic, and the anomalous Nernst effect (ANE) becomes non-negligible. Co2MnSi, a strong candidate for the spin generator in spin Seebeck devices, is a predicted half-metal with 100% spin polarisation at the Fermi energy, however, typically B2 or L21 order is needed to achieve this. We demonstrate the optimisation of thin film growth of Co2MnSi on glass, where choice of deposition and annealing temperature can promote various ordered states. The contribution from the ANE is then investigated to inform future measurements of the spin Seebeck. A maximum ANE coefficient of 0.662 µV K−1 is found for an A2 disordered polycrystalline Co2MnSi film. This value is comparable to ordered Heusler thin films deposited onto single crystal substrates but obtained at a far lower fabrication temperature and material cost.

Spin-selective response tunability in two-dimensional nanomagnet.

Abstract: Recent reports on the two-dimensional (2D) material CrOCl revealed magnetic ordering and spin polarisation with Curie Temperature Tc ~ 160 K, values higher than most diluted magnetic semiconductors. Here, we investigate the uniaxial and biaxial strain-dependent electronic and transport properties of CrOCl nanoribbon using first-principle based calculations. The calculated Young's modulus indicates high mechanical flexibility for the application of high strain. Our study shows that strain can induce material phase changes from a bipolar magnetic semiconductor → half metal → magnetic metal in the nanoribbon, leading to interesting spin-resolved conductance with 100% spin filtering. Furthermore, the current-voltage (I-V) response showed conductance fluctuations, characterised by peak-valley ratios and switching efficiency show high strain assisted tunability. Overall, CrOCl shows a highly anisotropic behaviour with the material displaying 100% spin polarisation in the tensile region. These electronic, transport and mechanical properties indicate that CrOCl is a versatile 2D material with multi-phase capabilities having promising applications for future nanospintronic devices.

GGA and GGA plus U study of half-metallic quaternary heusler compound CoCrScSn

Abstract: The structural, mechanical, electronic, magnetic, and half-metallic properties of quaternary Heusler compound CoCrScSn are studied using the GGA and GGA+U method based on first-principles calculations It is found that Type-I structure of CoCrScSn compound is the most stable, and its ground state is ferromagnetic At the equilibrium lattice constant, the electronic structures obtained by GGA and GGA+U methods indicate that CoCrScSn compound have typical half-metal character The results of elastic constants and half-metallic robustness show that the mechanical stability and half-metallicity of CoCrScSn can be well maintained in the range of 62 to 69 A under GGA and 57 to 64 A under GGA+U, respectively When CoCrScSn compound exhibits half-metallic properties, the total magnetic moment per molecular unit is 40 μB, which is in good agreement with the Slater-Pauling rule, and Cr atoms are the main source of molecular magnetic moment All the aforementioned results indicate that quaternary Heusler compound CoCrScSn would be an ideal candidate in spintronics

Robust intrinsic half-metallic ferromagnetism in stable 2D single-layer MnAsS4

Abstract: Two-dimensional (2D) intrinsic half-metallic materials are of great interest to explore the exciting physics and applications of nanoscale spintronic devices, but no such materials have been experimentally realized. Using first-principles calculations based on density-functional theory, we predicted that single-layer MnAsS4 was a 2D intrinsic ferromagnetic (FM) half-metal. The half-metallic spin gap for single-layer MnAsS4 is about 1.46 eV, and it has a large spin splitting of about 0.49 eV in the conduction band. Monte Carlo simulations predicted the Curie temperature (T c) was about 740 K. Moreover, within the biaxial strain ranging from -5% to 5%, the FM half-metallic properties remain unchanged. Its ground-state with 100% spin-polarization ratio at Fermi level may be a promising candidate material for 2D spintronic applications.

Structural, Magnetic, and Band Structure Characteristics of the Half-Metal–Type Heusler Alloys Co2VSi1−xAlx (x = 0, 0.25, 0.5, 0.75, and 1)

Abstract: We investigated the structural, magnetic, and band structure properties of the quaternary full Heusler compounds Co2VSi1−xAlx (x = 0, 0.25, 0.5, 0.75, and 1) by using full-potential linearized augmented-plane wave (FP-LAPW) method based on WIEN2k program The structural parameters are computed by the generalized gradient approximations (GGA) while for the electronic and magnetic properties, GGA and modified Becke–Johnson (mBj) schemes are used. It is shown that the equilibrium lattice constants and spin magnetic moment are in good agreement with the experimental values. The density of states (DOS) of Co2VSi and Co2VAl ternary full Heusler compounds shows a half-metallic character while for the Co2VSi1−xAlx (x = 0, 0.25, 0.5, 0.75, and 1), Heusler alloys exhibit a nearly half-metallic behavior with small spin-down at the Fermi level.

First-Principles Forecast of Gapless Half-Metallic and Spin-Gapless Semiconducting Materials: Case Study of Inverse Ti2CoSi-Based Compounds

Abstract: First-principles calculations were used to investigate several inverse Ti2CoSi-based compounds. Our results indicate that Ti2CoSi could transform from a spin-gapless semiconductor to a half metal if a quarter of the Co atoms are replaced by Ti. Ti2.25Co0.75Si would keep stable half-metallic properties in a large range of lattice parameter under the effect of hydrostatic strain, and would become a gapless half metal under the effect of tetragonal distortion. Furthermore, we substituted B, Al, Ga, P, As, and Sb for Si in the Ti2.25Co0.75Si compound. Our results demonstrate that Ti2.25Co0.75Si0.5B0.5, Ti2.25Co0.75Si0.5Al0.5, and Ti2.25Co0.75Si0.5Ga0.5 are half-metallic ferromagnetic materials, and Ti2.25Co0.75Si0.5P0.5, Ti2.25Co0.75Si0.5As0.5, and Ti2.25Co0.75Si0.5Sb0.5 are spin-gapless semiconducting materials. The introduced impurity atoms may adjust the valence electron configuration, change the charge concentration, and shift the location of the Fermi level.

Copper-doped induced ferromagnetic half-metal zirconium diselenide single crystals.

Abstract: Two dimensional (2D) magnetic layered materials have got considerable attention in memory storage devices due to their exciting magnetic ordering. Herein, the electronic and magnetic properties of high-quality single crystals zirconium diselenide and copper (Cu) doped zirconium diselenide grown through chemical vapor transport technique combined with first principle density functional theory calculation were investigated. A semimetallic state is recognized for Cu0.052Zr0.93Se2 as measured through resistance vs temperature measurements and angle resolved photoemission spectroscopy (ARPES). The magnetic measurement shows diamagnetic semiconductor behaviour for ZrSe2, whereas Cu0.052Zr0.93Se2 exhibits the ferromagnetic semimetal character using perpendicular magnetic field. Cu0.052Zr0.93Se2 reveals the room temperature magnetic moment ~0.0125 emu/g, while their Curie temperature is ~363.49K. Furthermore, first principle density functional theory (DFT) calculations shows energetically long range ferromagnetic ordering in half-metallic Cu-doped ZrSe2, while a diamagnetic state in case of ZrSe2 agrees well with experiment results. These results suggest that due to strong interaction at octahedral site of zirconium atoms when replaced by copper atoms, which can change the spin ordering of electrons and make zirconium vacancy, their magnetic moment is increased. Very importantly the half-metallic character of Cu0.052Zr0.93Se2 promote much spin polarized electron around the Fermi level, suggest significant potential in future memory devices and spintronic applications.

Electronic structures, magnetic properties and mechanical stability of half-metallic quaternary Heusler CoMnVTe

Abstract: The electronic structures, magnetic properties and mechanical stability of three configurations of a promising half-metallic quaternary Heusler compound CoMnVTe were systematically and comprehensively studied by the first-principle calculations. The results show that type-I and type-II configurations present half-metallic behavior with 100% spin polarization. Especially the type-I configuration has the most stable structure among these three configurations. The type-I, type-II configurations can maintain the half-metallic character within the lattice constant 5.47–6.12 A and 5.82–6.23 A, respectively. Anisotropy factor and three-dimensional (3D) Young’s modulus indicate that these three configurations of CoMnVTe compound are anisotropic. The type-I and type-II configurations own stable mechanical properties in some and all half-metallic lattice constant regions, respectively. The test results of strong correlation correction show that the U value has a visible effect on the half-metallic properties of the title compound. The (001)@VTe and (111)@V surfaces of type-I configuration also have half-metallic properties. The robust half-metallic properties and mechanical stability make the quaternary Heusler compound CoMnVTe a promising candidate for spintronic devices.

Thermoelectric and half-metallic behavior of the Co 2 TaAl: a DFT study

Abstract: The electronic, thermoelectric, optical and thermodynamic stability of the full-Heusler compound Co2TaAl is investigated under hydrostatic pressure in the range of (25.4 to − 26.3 GPa) within the framework of the density functional theory and the semi-classical Boltzmann theory using the generalized gradient approximation. The Co2TaAl compound in the minority spin is an n-type semiconductor with an indirect band gap of about 0.78 eV along Γ–X direction and a spin-flip gap of 0.6 eV. Applying stress led to decreasing the band gap turning the material to a p-type semiconductor; however, it remained n-type but with zero spin-flip gap under strain. The dimensionless Merit coefficient for the spin dn channel of Co2TaAl at equilibrium pressure obtained a large value of 0.98 at temperatures below 500 K. The optical properties of this compound, including refraction and reflection coefficients, absorption spectra, and real and imaginary parts of the dielectric function are studied in detail.

Robust and Efficient Electrical Injection of Spin-Polarized Carriers from a Zero-Spin-Gap Half-Metal V2NiAl into n-Si at Room Temperature

Abstract: In recent times, an engrossing and newly discovered class of materials with unique electronic band properties, namely, zero-spin-gap half-metal, has gained acute attraction worldwide because of its...

Tunable electronic structures and half-metallicity in two-dimensional InSe functionalized with magnetic superatom.

Abstract: Based on first-principles calculations, we investigate the geometric, energetic and electronic properties of two-dimensional (2D) InSe functionalized with magnetic superatoms (MnCl3). As a nonmagnetic semiconductor, 2D InSe exhibits non-covalent interaction with MnCl3 and provides an ideal substrate for the assembly of magnetic superatoms. We show that with a low coverage of MnCl3, the functionalized system behaves as a magnetic semiconductor with spin-polarized superatomic states residing inside the energy gap of InSe. When the coverage becomes higher, the system has one spin channel crossing Fermi level while the other remains insulating, thus being half-metallic. We further demonstrate electric field effects on the functionalized system, and reveal that half metal with 100% spin polarization can be achieved at a lower coverage due to the field induced charge transfer, which downshifts the unoccupied bands of one spin component so that they become partially filled. These findings are generally applicable, demonstrating the great promise of combining superatom assembly with electric gating for controllable and versatile 2D spintronics.

Transition between half-metal and ferromagnetic semiconductor induced by silicon vacancy in epitaxial silicene

Abstract: Since the inevitability in experimental synthesis, defects show great importance to many materials They will deeply regulate the properties of the materials, and then affect the further applications Thus, exploring the effects of defects on the properties of materials is desired Here, by using first-principles calculations, we systematically studied the effect of silicon vacancy defects on the properties of silicene generated on Nterminated cubic boron nitride (111) surface It is found that the introduction of silicon vacancy would trigger transition between half-metal and ferromagnetic semiconductor With small vacancy ratios of 1/36 and 1/24, the ground-state of the samples would behave as ferromagnetic semiconductors, and the band gaps are about 125 and 095 eV, respectively When the vacancy ratio is increased up to 1/6, the sample would turn into a ferromagnetic half-metal with a half-metallic gap of around 015 eV The change of the electronic structure of the samples is driven by the different electron transfer between silicon layer and substrate, ie, there will be different amount of electrons transferred from the silicon layer to the substrate when the vacancy ratio is altered This work would open a new way to regulate the properties of materials and extend applications in nanoelectronic field

Design of half-metal compensated antiferromagnets in Cu and Zn based full inverse Heusler alloys from 5-4 rule

Abstract: In this paper we are proposing 5-4 rule in the Cu and Zn based full inverse Heusler alloys with 9 electrons occupying the bands below the energy gap in the spin-down states. The 9 electrons will be distributed into 5 and 4 electrons between two atomic layers along the [001] direction of the tetragonal cell. We use the robustness of this 5-4 rule to design half-metallic antiferromagnets.