Robustness Of Half-metallicity Research Articles

Controllable half-metallicity in MnPX3 monolayer

Modulable electronic and magnetic structures significantly extend the properties and applications of two-dimensional (2D) materials. 2D antiferromagnets (AFM) can even become ferromagnets (FM) by various approaches, which ignites growing research interests in 2D AFM. Through first-principles calculations, we find that the adsorption of Li (electron doping) and F (hole doping) on the surface of MnPSe3 can induce half-metallicity with opposite spin polarizations. The adsorption site, concentration, charge transfer, and the exchange energy are investigated in detail, indicating the robustness of half-metallicity. At the interface of MnPS3/Au(111) heterostructure, we find electrons transfer from Au(111) to MnPS3, forming the Ohmic contact and inducing AFM-FM transition. All our results show that ferromagnetic MnPX3 (X = S and Se) monolayer with half-metallicity can be easily obtained, which may be of great significance in 2D spintronic materials and devices.

Robust half-metallicity and magnetic phase transition in Sr2CrReO6 via strain engineering

Using ab-initio calculations, the electronic and magnetic properties of double perovskite oxide {text{Sr}}_2 {text{CrReO}}_6 with two type of strains: biaxial (along the [110]-direction) and hydrostatic (along [111]-direction) are investigated. The ground state of the unstrained system is half-metallic ferrimagnetic, due to a strong antiferromagnetic (AFM) coupling between Cr and Re atoms within both (GGA and GGA+U) exchange-correlation potentials. It is demonstrated that the robustness of half-metallicity can be preserved under the influence of both biaxial and hydrostatic strains. Interestingly, a transition from ferri-to-ferromagnetic is established due to Re spin flipping to that of the Cr ion (i.e. Cr and Re spin becomes parallel) within the GGA+U method for both biaxial and hydrostatic tensile strains of ge +2%. The strong confinement of orbitals due to tensile strain results in the decrease of electron hopping which further reduced the AFM coupling strength between Cr and Re atoms, this leads to a ferri-to-ferromagnetic transition. However, the GGA scheme holds the ferrimagnetic state with both kinds of strains. This work shows that tensile strain is a feasible way to optimize the magnetic properties of perovskite oxides, which are presumed to be beneficial for spintronic technology.

Ab-Initio Investigations of Magnetic Properties and Induced Half-Metallicity in Ga1-xMnxP (x = 0.03, 0.25, 0.5, and 0.75) Alloys.

Ab-initio calculations are performed to examine the electronic structures and magnetic properties of spin-polarized Ga1−xMnxP (x = 0.03, 0.25, 0.5, and 0.75) ternary alloys. In order to perceive viable half-metallic (HM) states and unprecedented diluted magnetic semiconductors (DMSs) such as spintronic materials, the full potential linearized augmented plane wave method is utilized within the generalized gradient approximation (GGA). In order to tackle the correlation effects on 3d states of Mn atoms, we also employ the Hubbard U (GGA + U) technique to compute the magnetic properties of an Mn-doped GaP compound. We discuss the emerged global magnetic moments and the robustness of half-metallicity by varying the Mn composition in the GaP compound. Using GGA + U, the results of the density of states demonstrate that the incorporation of Mn develops a half-metallic state in the GaP compound with an engendered band gap at the Fermi level (EF) in the spin–down state. Accordingly, the half-metallic feature is produced through the hybridization of Mn-d and P-p orbitals. However, the half-metallic character is present at a low x composition with the GGA procedure. The produced magnetic state occurs in these materials, which is a consequence of the exchange interactions between the Mn-element and the host GaP system. For the considered alloys, we estimated the X-ray absorption spectra at the K edge of Mn. A thorough clarification of the pre-edge peaks is provided via the results of the theoretical absorption spectra. It is inferred that the valence state of Mn in Ga1−xMnxP alloys is +3. The predicted theoretical determinations surmise that the Mn-incorporated GaP semiconductor could inevitably be employed in spintronic devices.

Half-metallic completely compensated ferrimagnets in Cr doped BaP

On the basis of ab-initio calculations we have investigated the electronic and magnetic properties of Cr1-xBaxP alloy, our calculations suggest that as we dope BaP with Cr atoms and move towards Cr1-xBaxP where x=0, 0.125, 0.25, 0.50, and 0.75 all alloy are HM-FM. Interestingly Cr0.25Ba0.75P is a HM-AFM otherwise ‘fully compensated ferrimagnet’, this alloy should be of special interest for applications since it creates no external stray field and thus exhibit minimal energy losses. In addition, the robustness of half-metallicity with respect to the variation of lattice constants of Cr1-xBaxP is also discussed; moreover ferrimagnetism co-exists with the half-metallicity, resulting in the desired fully compensated half-metallic ferrimagnetism, for a wide range of lattice constants. Furthermore we found that this new HMFCF is stable according to its small formation energy.

Stability, electronic, magnetic and pressure effect of half-Heusler alloys CNaCa and SiNaCa: A first-principles study

We investigate the electronic and magnetic properties of CNaCa and SiNaCa by using full-potential local-orbital minimum-basis method. The calculations reveal the both alloys are half-metallic ferromagnets (HMF) with the same magnetic moment of 1.00μB per formula unit, the magnetic moment mainly originates from the strong spin-polarization of p electrons of C atom and partial involvement of d electrons of Ca atom. Both alloys have a large half-metallic gaps, even up to 0.609eV for CNaCa, meaning they are stable HMF at room temperature. The robustness of half-metallicity against the lattice constant is also calculated. Finally, lattice constant, magnetic moments, and electronic structure are calculated as a function of external pressure, which implies that the exchange splitting in crystal field gradually disappear and a transition occur from ferromagnetic to nonmagnetic states under a external pressure.

First-Principles Calculation of structural, electronic and magnetic properties of half-Heusler LiCaC and NaCaC compounds

The structural, electronic and magnetic properties of LiCaC and NaCaC compounds in half-Heusler structure have been studied using local density approximation (LDA) based on density functional theory (DFT). From the total energy calculation, it is found that the compounds LiCaC and NaCaC are stable in ferromagnetic phase. The spin-polarized electronic band structure and density of states of these compounds show that the minority spin channel has metallic nature and the majority spin channel has a semiconducting gap of 2.27 and 2.0eV for LiCaC and NaCaC respectively, resulting in a stable half-metallic ferromagnetic (HMF) behavior with magnetic moment of 1µB per formula unit. Analysis of density of states of these compounds indicates that the magnetic moment mainly originates from the strong spin-polarization of 2p like states of C and the hybridization between the C-2p like states and the Ca-3d like states. The robustness of half-metallicity against the lattice constant is also calculated. Presence of HMF in LiCaC and NaCaC compounds without any transition metal makes these compounds promising materials for spintronic applications.

Study of robust half-metallicity of Ga0.875Cr0.125As

Theoretical investigations of Cr doped GaAs in zinc blende phase are presented in this paper. The robustness of half metallicity of these compounds with correlation to their lattice compressions is discussed. Shifting of Fermi Level with compression of lattice constant is also addressed in this article. Results show that compounds exhibit their half-metallic nature (conductor for spin up state and semiconductor for spin down state) with their lattice compressions up to certain critical lattice constants. Abrupt changes in electronic and magnetic properties are observed for these robust transition lattice constants (RTLCs). These compounds lose their integer magnetic moments 4μB at RTLCs. Calculated RTLC for Ga0.875Cr0.125As is 5.03 A. Possible compressions in lattice constants from their relaxed states while maintaining their half-metallic nature is up to 4 %.

Ab-initio investigation of half-metallic ferromagnetism in half-Heusler compounds XYZ (X=Li, Na, K and Rb; Y=Mg, Ca, Sr and Ba; Z=B, Al and Ga)

The structural, electronic and magnetic properties of XYZ compounds (X=Li, Na, K and Rb; Y=Mg, Ca, Sr and Ba; Z=B, Al and Ga) in half-Heusler phase are studied by first principles calculations within density-functional theory. From the spin-polarized calculations, it is found that the compounds XCaB, XSrB, XBaB and LiBaGa are ferromagnetic and metallic whereas the other compounds XMgB, XYAl and XYGa except LiBaGa are non-magnetic and metallic. Among the compounds which exhibit ferromagnetism, XCaB and XSrB (X=Li, Na, and K) exhibit half-metallic (HM) property with an integer magnetic moment of 2.0μB per formula unit at their equilibrium volume. However, other compounds such as RbCaB, RbSrB and XBaB (X=Li, Na, K and Rb) are so-called nearly HMFs and exhibit HMF property at their expanded volume. The magnetic moment mainly originates from the strong spin-polarization of np electrons of Z (B and Ga) atoms and partial involvement of nd electrons of Y atoms. The robustness of half-metallicity against the lattice constant is also calculated. The absence of transition-metal atom makes these compounds important model systems for the study of origin and properties of half-metallic ferromagnetism of s–p electron systems.

First principles study of half-metallic ferromagnetism in zincblende Cd1−xVxSe

The structural, electronic and magnetic properties of zincblende (ZB) Cd1−xVxSe for different values of x were investigated using the full-potential linearized augmented plane wave plus local orbital (FPLAPW+lo) method based on spin-polarized density functional theory (DFT). It was confirmed that for all values of x, the ferromagnetic (FM) state is more stable than antiferromagnetic (AFM) state. The results show that Cd0.25V0.75Se and Cd0.5V0.5Se compounds exhibit a half-metallic (HM) characteristic while Cd0.75V0.25Se has nearly a HM nature. The obtained HM band gaps with EV-GGA have been considerably improved with respect to PBE-GGA scheme. The analysis of density of states (DOSs) curves confirms the hybridization between V d and Se p states in all compounds. The total magnetic moments of Cd0.25V0.75Se and Cd0.5V0.5Se compounds are 3μB (integer values), confirming their HM characteristic. Finally, the robustness of half-metallicity with changing the lattice parameters of Cd1−xVxSe alloys was discussed.

Half-metallic Ferromagnetism in the Rocksalt and Zincblende NaX (X=O, S, Se, Te, and Po)

The first-principles full potential linearized augmented plane wave method within spin-polarized density functional theory was used to investigate the structural, electronic, and magnetic properties of NaX compounds in the NiAs, rocksalt (RS), and zincblende (ZB) phases. The results showed that in all compounds, the stable state phase is a nonmagnetic (NM) NiAs structure except for NaO in which the stable state phase is a ferromagnetic (FM) RS structure. The ZB NaX (X=O, S, Se, Te, and Po) and RS NaX (X=O, S, and Se) structures are half-metallic (HM) ferromagnets with an integer magnetic moment of 1μB per formula unit. The half-metallicity originates from hybridization between X p and Na s and p states. The ZB NaO compound is a very robust half-metal which has the HM band gap of 1.25 eV and maintains HM characteristic up to above 40% of the lattice constant contraction. The half-metallicity is also found up to the lattice constant contraction of about 26.3%, 19.6%, 10.4%, and 7.5% for ZB NaS, NaSe, NaTe, and NaPo and 27.1%, 6.4%, and 1.7% for RS NaO, NaS, and NaSe, respectively. The robustness of half-metallicity with respect to the lattice contraction in the HM NaX compounds and their compatibility with the binary semiconductors make them suitable candidates in spintronic applications.

Electronic and magnetic properties of diluted magnetic semiconductors [formula omitted] in zincblende structure

The full-potential linearized augmented plane wave plus local orbital (FPLAPW + lo) method based on spin-polarized density functional theory (DFT) was used in order to investigate the structural, electronic and magnetic properties of ordered dilute ferromagnetic semiconductors Zn 1− x V x Se. The region of stability of ZB and NiAs phases in Zn 1− x V x Se alloys has been introduced by calculating the heat of formation for x different values. It was confirmed that for all x values, the ferromagnetism structure is more stable than antiferromagnetism in both phases. The results showed that in the ZB phase, VSe exhibits a metallic nature, Zn 0.5V 0.5Se exhibits a complete half-metal characteristic and Zn 0.25V 0.75Se and Zn 0.75V 0.25Se are nearly half-metal compounds. The calculated total magnetic moment of Zn 0.5V 0.5Se compound is 3 μ B , an integer value, confirming its half-metallic characteristic. In Zn 1− x V x Se alloys the atomic magnetic moments mainly arise from the V atom with a little contribution from the Se and Zn atoms. The robustness of half-metallicity with respect to the variation of lattice parameters of Zn 1− x V x Se alloys was discussed.

AB INITIO ELECTRONIC STRUCTURE CALCULATIONS OF HALF-METALLIC FERROMAGNETISM IN CALCIUM CHALCOGENIDES DOPED WITH B, C AND N

Self-consistent ab initio calculations were carried out to study the structural, electronic and magnetic properties of nine ternary compounds Ca 4 XA 3 ( X = B , C and N ; A = S , Se and Te ). The calculations were performed by using tight-binding linear muffin tin orbital (TB-LMTO) method within the local density approximation (LDA). The calculations reveal that half-metallic ferromagnetism can be obtained for C - and N -doping with the integer magnetic moment of 2.00 μ B and 1.00 μ B per cell. However, B substitution does not induce magnetism in CaS and CaSe systems, but it produces ferromagnetism in CaTe system with magnetic moment of 2.67 μ B per cell. Moreover C - and N -doping enhance the stable ferromagnetic state in calcium chalcogenide systems. Spin-dependent electronic band structure, total and partial densities of state calculations demonstrate that localized magnetic moments substantially come from impurity atoms. Half-metallic ferromagnetism predominately originates from spin-polarization of electrons in 2p orbital states of C and N atoms. In addition, equilibrium lattice constant, bulk modulus, atomic local magnetic moments, half-metallic gap and robustness of half-metallicity have been calculated.

Half-metallic ferromagnetism in wurtzite MC ( [formula omitted], Sr, Ba and Mg)

The first-principles full-potential linearized augmented plane-wave method within density-functional theory is used to investigate electronic structure and magnetism of wurtzite (WZ) crystal structure MC (M=Ca,Sr,Ba and Mg). It is shown that the WZ CaC, SrC and BaC are half-metallic ferromagnets with a magnetic moment of 2 μ B per formula unit, whereas MgC shows the metallic character. The half-metallicity is also found to be robust with respect to the lattice compression and is maintained up to the lattice constant contraction of 12%, 21%, and 8% for WZ CaC, SrC and BaC, respectively. The large HM gaps (0.54–0.81 eV) and robustness of half-metallicity with respect to the lattice change make these materials possible candidates for spin injection in spintronic devices.

First-principles study of half-metallic ferromagnetism in Zn 1−xCr xSe

The first-principles full-potential linearized augmented plane-wave method within the generalized gradient approximation for the exchange–correlation functional is used to investigate the structural, electronic and magnetic properties of Zn 1− x Cr x Se ( x=0.25, 0.5, 0.75 and 1.0). We find that Zn 1− x Cr x Se exhibits a half-metallic characteristic, and the ferromagnetic state is more favourable in energy than the antiferromagnetic state. The calculated total magnetic moment of Zn 1− x Cr x Se per Cr atom is 4.00 μ B, which mainly arises from the Cr atom with a little contribution from the Se and Zn atoms. Furthermore, the robustness of half-metallicity with respect to the variation of lattice constants of Zn 1− x Cr x Se is discussed.

Half-metallic ferromagnetism in the zinc-blende MC (M = Li, Na and K)

The electronic structure and magnetic properties of zinc-blende structure MC (M = Li, Na, and K) are investigated by using the first-principles full-potential linearized augmented plane-wave method. The results show that LiC, NaC and KC are half-metallic ferromagnets with a magnetic moment of 3μB per formula unit. The half-metallicity is also found to be robust with respect to the lattice compression and is maintained up to the lattice-constant contraction of 11% and 20% for ZB NaC and KC, respectively. The large magnetic moment and robustness of half-metallicity with respect to the lattice contraction make these materials possible candidates for spin injection in spintronic devices.