Half-metallic Properties Research Articles

Structural, electronic, and magnetic properties of CrMnX (X = Ge, Se, Si, and Sn) compounds

We have studied the structural, electronic, and magnetic properties of CrMnX (X = Ge, Se, Si, and Sn) compounds. The first principles band structure calculation within the framework of density functional theory was used to explore these properties. The full-potential linearized augmented plane wave (FP-LAPW) method as implemented in the Wien2k software package has been used. We investigated the effect of compositional variation on lattice constants, bulk modulus, electronic, and magnetic properties. CrMnSi has the largest while CrMnSe has the smallest bulk modulus among the studied compounds. Our calculated electronic and magnetic properties for CrMnX (X = Ge, Se, Si, and Sn) compounds show that CrMnGe, CrMnSe, and CrMnSi are half-metallic materials with integer magnetic moments while CrMnSn has metallic behavior. These compounds are fascinating for spintronic devices due to their half-metallic properties.

Half-metallicity in CrAl-terminated Co2CrAl thin film

Half-metals with high Curie temperature are ideal candidates for applications in spin-based electronics—an emerging technology utilizing a spin degree of freedom in electronic devices. Many half-metallic materials have been predicted theoretically, and some have been confirmed experimentally. At the same time, in thin-film geometry the electronic structure of these materials may change due to the potential presence of surface/interface states. This could limit practical applications of these materials in nano-size devices, since typically these states result in reduced spin-polarization. Here, from first principles we study a full Heusler compound, Co2CrAl in thin film geometry. This material has been studied extensively, and it has been reported that it exhibits half-metallic properties in the bulk. We show contrary to the earlier reports that this material retains 100% spin polarization in CrAl-terminated thin film geometry (Co-termination results in destroyed half-metallicity). Moreover, we confirm that under biaxial strain Co2CrAl retains half-metallicity for a practically feasible range of considered pressure, i.e. in principle it may stay half-metallic if used in thin-film heterostructures, where lattice mismatch is a common scenario. The magnetic alignment of Co2CrAl is confirmed to be ferromagnetic, with the non-integer total magnetic moment of Co-terminated cell, and the integer total magnetic moment of CrAl-terminated cell, consistent with their corresponding non-half-metallic and half-metallic electronic structures. If confirmed experimentally, these results may have an important impact in spin-based electronics.

Density Functional Theory Study of Defect Induced Ferromagnetism and Half-Metallicity in CaI2 Based Monolayer for Spintronics Applications

With the rapid advancement of electronics and spintronics industries, the demand for highly efficient materials has been increased for the application of high speed devices and circuits. In the recent past, Ca-based systems have been studied for superconducting properties. Using first-principles density functional theoretical calculations, we have investigated another Ca-based system (CaI2) for its half-metallic properties, which can be promising for ultrafast nonscattering transport. In the domain of spintronics, main group based half-metallic materials have attracted much attention due to their long spin-relaxation time. Here, in this study, we report for the first time ferromagnetism and half-metallicity in calcium iodide (CaI2) based materials with a wide spin-up gap of ∼3.84 eV. Such high spin-up gap in Ca-based half-metallic material is very promising since it can provide nonscattering transport. Among all, Ca0.67δ0.33I2 has a similar pattern to the most well established and thinnest magnet, CrI3 monolayer. Our further investigation predicts that the Ca0.89δ0.11I2 system has a ferromagnetic ground state with Curie temperature of ∼238 K (XY model), which is considerably higher than the reported CrI3 monolayer (45 K). Further to this, such system has a high magnetic anisotropy energy (∼14.11 meV), which indicates that it can prohibit spin fluctuation. Therefore, we report here that alkaline earth metal halide based magnetic materials can be promising for next generation spintronics devices.

Half metallic ferromagnetic and optical properties of ruthenium-doped zincblende ZnS: A first principles study

Magnetic and optical properties of Ru-doped ZnS have been investigated using first principles calculations. Due to Ru dopants, nonmagnetic ZnS becomes magnetic. Ru induces half metallic ferromagnetism with a total magnetic moment of 2.0μB/supercell. Furthermore, the origin of ferromagnetism in Ru-doped ZnS can be explained by Ruderman-Kittel-Kasuya-Yosida (RKKY) like exchange interaction. Curie temperature analysis indicates the possibility of room temperature ferromagnetism from the structures. Moreover, reflectivity spectra in optical calculations successfully describe the metallic properties introduced in the doped system. Static dielectric constant for 6.25% Ru doping gives approximately six times higher value in long wavelength limit compared to the pristine. With a significant amount of Ru, the doped system becomes efficient for visible light absorption. The study reveals that Ru-doped ZnS can be a promising candidate for potential applications in spintronic and optoelectronic devices.

Effects of Strain on the Half-Metallic and Elastic Properties of FeCrTe and CoCrSi with Clb Structure

The effects of strain on the half-metallic (HM) and elastic properties of FeCrTe and CoCrSi alloys with Clb structure were calculated using a first-principles calculation. Both compounds showed (HM) property with full spin polarization, and this property can be present when their lattice constants are in the range from 5.18 Å to 5.71 Å for CoCrSi, and 5.25 Å to 6.05 Å for FeCrTe. The calculations of elastic properties show that both compounds are mechanically stable, ductile and hard with varied properties. In addition, calculations of the elastic characteristics for the above ranges for both FeCrTe and CoCrSi alloys showed mechanical stability, therefore, the FeCrTe and CoCrSi alloys are likely to be composed in experimental applications.

Half-metallic properties of KP compound in a bulk and (001) surface of rock-salt structure: A b-initio study

Half-metallic properties of KP compound in a bulk and (001) surface of rock-salt structure: A b-initio study

Ferromagnetic half-metal properties of two dimensional vertical tellurene/VS2 heterostructure: A first-principles study

Vertical integration of two-dimensional (2D) materials has recently emerged as an exciting method for the design of electronic and optoelectronic devices. Searching for ferromagnetic (FM) Van der Waals (vdW) heterostructures with high Curie temperature and multiple-band alignments is crucial to develop next-generation spintronic and optoelectronic nanodevices. In this work, first-principles calculations are employed to explore the structural and electronic properties of vertical tellurene/VS2 vdW heterostructure, and the FM vdW heterostructure is found in the tellurene/VS2 heterobilayer with Curie temperature of 150 K and type-III alignment. The ferromagnetic half-metal properties of two dimensional vertical tellurene/VS2 heterostructure provide the possibilities of realizing the high-temperature FM vdW heterostructures in practice.

Investigation of half-metallic and magnetic phase transition in Co2TiZ (Z = Al, Ga, In) Heusler alloys

ABSTRACTThe half-metallic and ferromagnetic properties of Co2TiZ (Z = Al, Ga, In) Heusler alloys are investigated. The structural stability is analyzed among the two possible structures, namely, L21 (Cu2MnAl phase) and XA (Hg2CuTi phase) structures. It is found that these alloys are stable in L21 (Cu2MnAl phase) structure. The electronic structure of Co2TiZ reveals that these alloys exhibit half-metallic ferromagnetism with small spin-flip gap at the minority spin state. As the pressure is increased, ferromagnetic to non-magnetic phase transition is observed at the pressures of 380.9, 363.0 and 317.8 GPa for Co2TiAl, Co2TiGa and Co2TiIn, respectively. Half-metallic to metallic phase transition occurs in Co2TiAl, Co2TiGa and Co2TiIn at the pressures of 76.5 GPa, 73.1 GPa and 63.9 GPa respectively.

Electronic, magnetic, and optical properties of Mn-doped GaSb: A first-principles study

Half-metallic ferromagnets can produce fully spin-polarized conduction electrons and can be applied to fabricate spintronic devices. Thus, in this study, the electronic structure, magnetic properties, and optical properties of GaSb, which has exhibited half-metallicity, doped with Mn, a 3d transition metal, are calculated using the generalized gradient approximation and Heyd-Scuseria-Ernzerhof (HSE) functional. Ga1−xMnxSb (x = 0.25, 0.5, 0.75) materials exhibit ferromagnetic half-metallic properties and a high Curie temperature, indicating that this series can be applied in spintronic devices. Meanwhile, they absorb strongly in the infrared band, suggesting that Ga1−xMnxSb also has potential applications in infrared photoelectric devices.

Electronic and Magnetic Properties of Fe2−xCoxTiSi (x = 0, 0.5, 1, 1.5, 2) Heusler Alloys

The first principles calculations are carried out to understand the half metallic and ferromagnetic properties of Fe2−xCoxTiSi (x = 0, 0.5, 1, 1.5, 2) full Heusler alloys. The stable structure is predicted as L21 structure (Cu2MnAl phase). The lattice constant value of Fe2−xCoxTiSi Heusler compounds increases as the value of x increases. These alloys exhibit half metallic ferromagnetism (except Fe2TiSi) with small spin flip gap at the minority spin state. At high pressure, semiconductor to metallic phase transition is observed in Fe2TiSi while half metallic to metallic phase transition is observed in Fe1.5Co0.5TiSi, Fe1.0 Co1.0TiSi, Fe0.5Co1.5TiSi and Co2TiSi. The spin polarization of these compounds (except Fe2TiSi) is 100%. Hence, these compounds are suitable for spin injection devices in spintronics.

Current-perpendicular-to-plane giant magnetoresistance effects using Heusler alloys

A half-metal is an ideal spin source to realize extremely large magnetoresistance effects because of the completely spin-polarized density of states at the Fermi level, and Heusler alloy is a material class for which several compositions are known to exhibit half-metallic properties. Current perpendicular-to-plane (CPP) giant magnetoresistance (GMR) effect is a resistance change that depends upon the relative angle of the magnetization vectors in magnetic layers separated by thin non-magnetic layer(s), which can be utilized for magnetic sensor applications. Over the last decade, the resistance change of CPP-GMR has been found to enhance greatly when using half-metallic Heusler alloys. In this article, the history of Heusler alloy based CPP-GMR is briefly reviewed, including the authors’ recent results on the analysis of the spin asymmetry coefficients based on the Valet-Fert model. Finally, the degradation of half-metallic spin polarization at interfaces is discussed and a future prospect is described.

Half-metallic property with Dirac-like crossings in synthesized rhombohedral-type PrNiO3 material and influence of uniform strain, hole and electron doping, and spin-orbit coupling on its electronic structures

Abstract Several R 3 ¯ c Dirac half-metallic materials have been proposed and investigated based on first principles. A certain energy value in one spin channel with a clear band gap in the other spin channel leads to the half-metallic properties of these materials and multiple linear band dispersions (Dirac-like crossings) around the Fermi level for fast and low energy consumption electron transmission. In this work, a material synthesized in a prior experiment, PrNiO3, was found to be a novel half-metallic material with multiple Dirac-like band dispersions according to the first principles. In this work, four magnetic states, i.e., ferromagnetic (FM), nonmagnetic (NM), and antiferromagnetic (AFM-1 and AFM-2) were considered in the 1 × 1 × 1 unit cell of PrNiO3. Two cases of superlattices, 1 × 1 × 2 and 2 × 2 × 1, were built to study the most stable magnetic state of these systems. We found that the FM is the most stable magnetic state for the 1 × 1 × 1, 1 × 1 × 2, and 2 × 2 × 1 systems. The effects of uniform strain, hole and electron doping, and spin-orbit coupling on its electronic structures were discussed in detail. We hope this work can encourage more experimental and theoretical research on R 3 ¯ c -type half-metallic materials with multiple Dirac-like band dispersions.

First-principles calculations on half-metal ferromagnetic results of VZrAs and VZrSb half-heusler compounds and Al1-xMxAs (M= Co, Fe and x = 0.0625, 0.125, 0.25) diluted magnetic semiconductors

The theoretical calculations on structural, electronic, half-metallic and elastic properties of both VZrAs, VZrSb half-Heusler compounds and Al1-xFexAs and Al1-xCoxAs (x = 0.0625, 0.125, 0.25) diluted magnetic semiconductors (DMSs) have been investigated using WIEN2k. In Al1-xFexAs and Al1-xCoxAs (x = 0.0625, 0.125, 0.25) DMSs, the ferromagnetic phases are more stable than non-magnetic and antiferromagnetic phases. In VZr(As, Sb) compounds, the ferromagnetic (FM) phases in Type II structure are more stable energetically. The spin-up electrons of both half-Heusler compounds have semiconducting nature with 0.643 and 0.799 eV energy gaps while spin-down electrons of Al0.875Fe0.125As, Al0.9375Fe0.0625As and Al1-xCoxAs (x = 0.0625, 0.125, 0.25) DMSs have semiconducting feature. The mechanically stability conditions are provided by all compounds except VZrAs half-Heusler compound. Therefore, VZrSb, Al1-xFexAs and Al1-xCoxAs (x = 0.0625, 0.125, 0.25) diluted magnetic semiconductors (DMS) are mechanically stable against the deformation. The VZrAs compound can be deformed in the experimental process since it does not provide the C11 > C12 mechanical stability condition. According to conditions of the ductility or brittleness of polycrystalline material, both VZrAs and VZrSb half-metal compounds are ductile materials while Al1-xFexAs and Al1-xCoxAs (x = 0.0625, 0.125, 0.25) DMSs are brittle. Finally, VZr(As, Sb), Al1-xCoxAs (x = 0.0625, 0.125, 0.25) and Al1-xFexAs (x = 0.0625, 0.125) compounds were obtained true half-metal ferromagnetic materials (HMF) within 4.00, 2.00 and 5.00 μB/f.u.

Topologically protected states and half-metal behaviors: Defect-strain synergy effects in two-dimensional antimonene

Two-dimensional (2D) materials often feature defects and strain, due to their atomic layered character, which can cause problems for applications. Antimonene, a monolayer material derived from layered bulk Sb, undergoes a semiconductor-to-topological-insulator transition under large strain. However, it is unclear whether the structure and properties of antimonene are retained under strain once defects are generated. Here, we used ab initio calculations to explore a series of the most probable defects in these materials, including the Stone-Wales (SW) defects, single vacancies, double vacancies (DV), and adatoms. Interestingly, the influence of defects can be categorized into two types: for defects involving the loss/addition of an odd number of atoms, the material becomes ferromagnetic and exhibits half-metal properties under a certain strain; for defects involving an even number of missing atoms, the material remains a nonmagnetic semiconductor. Moreover, the topological phase transitions are robust for Sb monolayers with SW defects, but the critical transition strain decreases. Conversely, topological phase transitions might vanish for DV (555|777) and DV (5|8|5) defects. Our calculations suggest that different types of defects and strain might transform antimonene into a semiconductor, half-metal, or topological insulator. Therefore, defects and strain effects in antimonene should be carefully controlled for its applications.

A study on magnetic, electronic, elastic and vibrational properties of Ir2MnAl Heusler alloy for spintronic applications

The magnetic, electronic, elastic and vibrational properties of Ir2MnAl Heusler alloy are investigated with generalised gradient approximation (GGA) within the frame of Density Functional Theory (DFT). The ferromagnetic (FM) and non-magnetic (NM) states of Ir2MnAl Heusler alloy in Cu2MnAl and Hg2CuTi crystal structures have been compared. It is found that the ferromagnetic state in the Cu2MnAl structure is energetically more stable than other states. The obtained structural parameters are consistent with the current experimental and theoretical results. The spin-polarised electronic band structures of the material exhibit half-metallic behaviour with band gap in spin minority state from 0.382 eV at the Γ-X symmetry points, making it useful for spintronics applications. The calculated total magnetic moment of Ir2MnAl Heusler alloy is 4 μB which comply with the Slater-Pauling rule. Furthermore, the uniform strain has also been implemented to examine the magneto-electronic and half-metallic properties of this alloy. As a result, the half-metallicity is preserved in lattice constants between 5.872 Å and 6.187 Å. The obtained negative formation energy indicates both energetic and thermodynamic stability of this alloy. Moreover, the computed elastic constants state that this material is mechanically stable since it fulfills the Born stability criteria. The calculated B/G ratio and Cauchy pressure imply that Ir2MnAl is a ductile material in nature. Additionally, the vibrational properties are studied and it is found that this material is dynamically stable since there is no negative frequency value in phonon dispersion curves.

Tunable electronic structures, half-metallicity and optical properties in Fe-NM (NM=B, C, N) co-doped monolayer 2H–MoSe2

Exploring two-dimensional (2D) graphene-like materials with magnetic characteristics has attracted intense research interest. Here, based on spin-polarized density functional theory calculations, the tunable electronic structures, half-metallicity and optical properties can be realized in the 2D monolayer MoSe2 by Fe-NM (NM=B, C, N) codoping. The results indicate that the Fe-doping and Fe–B codoping exhibit a robust magnetic half-metallicity, which can be attributed to that the electrons partially occupy the bonding state consisting of Fe e1 and Fe a1 states at the Femi level (EF). The Fe–N codoping exhibits a magnetic semiconductor character due to the strong hybridization between Fe dxy, dz2 states and N pz state. However, the Fe–C codoping shows a non-magnetic ground state due to the effective charge compensation between Fe and C atoms. The Fe-NM codoping can effectively tune the optical properties of monolayer MoSe2 by the introducing of impurity levels near the EF. A stronger and wider absorption in the visible region of 1.8–3.2 eV is observed, which is in favor of the visible light devices and potential solar absorbers. The distinctive magnetic half-metallicity, electronic and optical properties for the Fe-NM co-doped monolayer MoSe2 have great prospects in the fields of spintronics, opto-electronics and magneto-optics devices.

Halfmetallicity, mechanical and thermodynamic study on iridium based compounds by First Principles calculations

Using First Principles calculations as implemented in Wien2K, Electronic structure, Magnetic, Half-Metallic, Mechanical and thermodynamic properties has been studied for Ir2MnAl and Ir2MnGa full Heusler alloys. Structural optimization was performed for nonmagnetic (NM), Ferromagnetic (FM) and antiferromagnetic (AFM) states using LSDA as exchange-correlation potential. Both the alloys were found to be stable in FM states. These alloys have satisfied Born mechanical stability criteria in ferromagnetic L21 structure. Elastic constants, Mechanical properties, and thermodynamic properties were calculated. They reveal that these alloys being incompressible, ductile and anisotropic. Ir2MnAl exhibited half metallicity with 100% spin polarization, while, Ir2MnGa was observed to be metallic with 96% spin polarization. The total spin magnetic moment per unit cell of both the alloys satisfy Slater-Pauling rule with 4 μB and 4.02 μB for Ir2MnAl and Ir2MnGa respectively. Ir2MnAl was observed to be a half-metallic ferromagnet with an indirect energy gap of 0.25eV. Curie temperature was calculated using the mean field approximation method to be 110K for Ir2MnAl. Since the calculated value of Curie temperature is low, Ir2MnAl, would not be suitable for room temperature spintronic devices.

Half-Metallic Property Induced by Double Exchange Interaction in the Double Perovskite Bi2BB'O6 (B, B' = 3d Transitional Metal) via First-Principles Calculations.

In this paper, we identify three possible candidate series of half-metals (HM) from Bi-based double perovskites Bi2BB′O6 (BB′ = transition metal ions) through calculations utilizing the density functional theory (DFT) and full-structural optimization, in which the generalized gradient approximation (GGA) and the strong correlation effect (GGA + U) are considered. After observing the candidate materials under four types of magnetic states, i.e., ferromagnetic (FM), ferrimagnetic (FiM), antiferromagnetic (AF), and nonmagnetic (NM), we found eight promising candidates for half-metallic materials. Under the GGA scheme, there are three ferromagnetic-half-metal (FM-HM) materials, Bi2CrCoO6, Bi2CrNiO6 and Bi2FeNiO6, and three FiM-HM materials, Bi2FeZnO6, Bi2CrZnO6 and Bi2CoZnO6. With implementation of the Coulomb interaction correction (GGA + U), we find two stable half-metallic materials: Bi2CrNiO6 and Bi2CrZnO6. We determine that the stability of some of these materials are tied to the double exchange interaction, an indirect interaction within the higher powers of localized spin interaction among transition metals via oxygen ions. Found in half-metallic materials, and especially those in the ferromagnetic (FM) state, the double exchange interaction is recognized in the FM-HM materials Bi2CrCoO6 and Bi2FeNiO6.

Effect of doping chromium on electronic and magnetic properties of ZnS monolayer: a DFT study

Density-functional theory has been applied to investigate the electronic and magnetic properties of the pure and chromium-doped ZnS nanosheets via examining a number of important indicators including the electronic band structure and density of states. It is found that the pure nanosheet is a semiconductor with a band gap of about 2.525 eV. Moreover, the effect of doping the chromium atom is manifested in the form of reduction in the value of the band gap to 1.85 eV, which results in half-metallic properties for the ZnS nanosheet. Most importantly, it is verified that the chromium-doped nanosheet has an intermediate band, which can be utilized in fabricating more advanced solar cells with a high rate of photon absorption and state-of-the-art lasers with a high quantum performance.

First-principles calculations to investigate structural, electronic, half-metallic and thermodynamic properties of hexagonal UX2O6 (X=Cr,V) compounds

Abstract Full potential linearized augmented plane wave plus local orbital's (FP-LAPW + LO) method within density functional theory (DFT) is used to investigate the structural, electronic and half-metallic properties of hexagonal UX2O6 (X = Cr,V). Features such as the lattice constant (a and c), bulk modulus and its pressure derivative are reported. The calculated lattice parameters are in good agreement with available experimental results. Band structure and overall densities of states have proved UV2O6 as an indirect half-metallic material with a band gap of 2.88 eV and UCr2O6 as a magnetic semiconductor. The results obtained, make the hexagonal UX2O6 a candidate material for future spintronic applications. Based on the quasi-harmonic Debye model, the thermodynamic properties of the material in question have been predicted taking into account of the lattice vibrations. The variation of the lattice constant, bulk modulus and heat capacity as a function of pressure in the range 0–40 GPa and temperatures of 0–1500 K is computed. Our findings show that external effects are highly effective in tuning some of the macroscopic properties of the compounds under study.