Origin Of Half-metallicity Research Articles

The Origin of Half-Metallicity in SrO Doped with Transition Metal Atoms Silver and Gold: a First Principles Calculations

In this GGA study, electronic and magnetic properties were investigated with the implementation of the FP-LAPW method within the framework of DFT. Resulting compounds Ag0.125Sr0.875O and Au0.125Sr0.875O were formed by substituting transition metal atoms silver and gold in strontium oxide with 12.5% concentration. Formation energy values show the compounds are stable in the ground state. Volume optimization curves predict the doped compounds are stable in the ferromagnetic phase. Total DOS and band structure plots display half-metallicity at the Fermi level, and also magnetic moment was found in the supercells.

Exploration of electronic structure, mechanical stability, magnetism, and thermophysical properties of L21structured Co2XSb (X = Sc and Ti) ferromagnets

The origin of half-metallicity, structural, thermoelectric, elasto-mechanical, and thermodynamic properties of Co2ScSb and Co2TiSb full-Heuslers has been examined by full potential methods. Structural optimizations support the stability of both alloys in AlCu2Mn-prototype with space symmetry of (#225) space group. The occurrence of perfect band occupation and interpretation of density of states through the modified version of the Becke Johnson (mBJ) scheme for both these Heusler systems delivers more precise and accurate results rather than GGA and GGA + U. The density of states and band occupation describes the semiconducting nature with an indirect band-gap 1.08 eV for Co2ScSb and 1.32 eV Co2TiSb. Robustness of various elastic constants against external forces is checked to descripted stability of these alloys. The evaluation of elastic constants and its other associated mechanical constituents reveals ductile behavior along with high melting temperature. The thermoelectric coefficients are used to check the applicability of the material for waste heat recovery systems and technological purposes. Thermal parameters support the material's low anharmonicity and hence predict the stability of these alloys at the wide range of temperatures and pressure. The thermoelectric parameters pose its applications and stand to develop devices based on spintronics and thermoelectric purposes.

Origin of half-metallicity in XCrBi (X = Hf,Ti, and Zr) half-Heusler alloys

First principles calculation has been employed to investigate the physical properties and thermodynamic properties of XCrBi (X = Hf, Ti and Zr) half-Heusler alloys. The half Heusler alloys TiCrBi and ZrCrBi studied are found to possess half-metallic character except HfCrBi showing metallic behaviour in both spin up and spin down channel. The Slater-Pauling rule is uesd to predicted the total magnetic moment of 3μB which confirmed the values from calculation. All half Heusler alloys are mechanically and thermodynamically stable.

Half-Metallic Characteristic in the New Full–Heusler SrYO2 (Y = Sc, Ti, V, and Cr)

Half-metallic properties of SrYO2 (Y = Sc, Ti, V, and Cr) full-Hensler compounds were studied using full-potential linearized augmented plane wave method based on density functional theory. The negative formation energies of SrYO2 (Y = Sc, Ti, V, and Cr) alloys confirmed that they can be synthesized experimentally. Total energy calculations showed that AlCu2Mn-type structure was the ground state structure in all compounds. In both structures, SrYO2 (Y = Ti, V, and Cr) alloys were half-metallic ferrromagnets, while SrScO2 was a non- magnetic metal. The origin of half-metallicity was verified for SrCrO2. SrYO2 (Y = Ti, V, and Cr) alloys in both structures were half-metals in a wide range of lattice constants indicating that they are quite robust against hydrostatic strains. The magnetization of SrYO2 (Y = Ti, V, and Cr) alloys was mainly originated from the 3d electrons of Y (= Ti, V, and Cr) atoms and followed the Slater–Pauling rule: Mtot = Ztot – 12. Generally, It is expected that SrYO2 (Y = Ti, V, and Cr) alloys are promising and interesting candidates in the future spintronic field.

Half-metallic characteristic in the new full-Heusler SrYO-=SUB=-2-=/SUB=- (Y = Sc, Ti, V and Cr) -=SUP=-*-=/SUP=-

AbstractHalf-metallic properties of SrYO_2 (Y = Sc, Ti, V, and Cr) full-Hensler compounds were studied using full-potential linearized augmented plane wave method based on density functional theory. The negative formation energies of SrYO_2 (Y = Sc, Ti, V, and Cr) alloys confirmed that they can be synthesized experimentally. Total energy calculations showed that AlCu_2Mn-type structure was the ground state structure in all compounds. In both structures, SrYO_2 (Y = Ti, V, and Cr) alloys were half-metallic ferrromagnets, while SrScO_2 was a non- magnetic metal. The origin of half-metallicity was verified for SrCrO_2. SrYO_2 (Y = Ti, V, and Cr) alloys in both structures were half-metals in a wide range of lattice constants indicating that they are quite robust against hydrostatic strains. The magnetization of SrYO_2 (Y = Ti, V, and Cr) alloys was mainly originated from the 3 d electrons of Y (= Ti, V, and Cr) atoms and followed the Slater–Pauling rule: M _tot = Z _tot – 12. Generally, It is expected that SrYO_2 (Y = Ti, V, and Cr) alloys are promising and interesting candidates in the future spintronic field.

Study of Electronic Structure, Magnetism, and Half-Metallicity of New Heusler Compounds CsTmO2 (Tm = Fe, Co, Ni, and Cu)

The density functional calculations were performed using the full-potential linearized augmented plane wave (FPLAPW) method for new Heusler alloys CsTmO2 (Tm = Fe, Co, Ni, and Cu). All compounds were stable in FM AlCu2Mn-type structure. Results revealed that these alloys can be experimentally synthesized according to the calculated cohesive and formation energies. CsTmO2 (Tm = Fe, Co, Ni, and Cu) alloys in AlCu2Mn-type and CuHg2Ti-type structures were half-metallic ferromagnets. The origin of half-metallicity in CsNiO2 alloy was also discussed. The total magnetic moment of CsTmO2 (Tm = Fe, Co, Ni, and Cu) alloys in both structures were 3 μB per formula unit and obeyed the Slater-Pauling rule (Mtot = 22 − Ztot). The relationship between the magnetism and half-metallicity of all compounds and the lattice constants was also studied. The half-metallic character in combined alloys CsTmO2 (Tm = Fe, Co, Ni, and Cu) improved in comparison with Heusler alloys including transition metals which indicated that they may be good candidates for practical applications in spintronics.

First-principles study of half-metallic properties in RbCaNZ (Z = O, S, and Se) quaternary Heusler compounds

On the basis of first principles calculations, the electronic structures and magnetic properties of quaternary Heusler alloys RbCaNZ (Z = O, S, and Se) were studied. The negative formation energies indicated that all these compounds were thermodynamically stable and thus may be experimentally synthesized at appropriate conditions in the future. The results showed that YI structure was the most favorable configuration among the three possible structures. All compounds were found to be half-metallic ferromagnets. The characteristic of energy bands and origin of half-metallicity were also verified. The total magnetic moments of RbCaNZ (Z = O, S, and Se) compounds were obtained 2μB per formula unit, which were in an agreement with Slater-Pauling rule (Mtot = 12 − Ztot). Half-metallicity was preserved at ranges of 5.06–8.36 Å, 5.96–8.81 Å, and 6.13–8.73 Å for RbCaNO, RbCaNS, and RbCaNSe compounds, respectively, which show that these quaternary Heusler compounds may be potential candidates in spintronic applications.

Half-metallic ferromagnetism in $$\text {Ti}_{2}\text {IrZ}$$Ti2IrZ (Z $$=$$= B, Al, Ga, and In) Heusler alloys: A density functional study

The first-principle density functional theory (DFT) calculations were employed to investigate the electronic structures, magnetic properties and half-metallicity of \(\text {Ti}_{2}\text {IrZ}\) (Z \(=\) B, Al, Ga, and In) Heusler alloys with \(\text {AlCu}_{2}\text {Mn}\)- and \(\text {CuHg}_{2}\text {Ti}\)-type structures within local density approximation and generalised gradient approximation for the exchange correlation potential. It was found that \(\text {CuHg}_{2}\text {Ti}\)-type structure in ferromagnetic state was energetically more favourable than \(\text {AlCu}_{2}\text {Mn}\)-type structure in all compounds except \(\text {Ti}_{2}\text {IrB}\) which was stable in \(\text {AlCu}_{2}\text {Mn}\)-type structure in non-magnetic state. \(\text {Ti}_{2}\text {IrZ}\) (Z \(=\) B, Al, Ga, and In) alloys in \(\text {CuHg}_{2}\text {Ti}\)-type structure were half-metallic ferromagnets at their equilibrium lattice constants. Half-metallic band gaps were respectively equal to 0.87, 0.79, 0.75, and 0.73 eV for \(\text {Ti}_{2}\text {IrB}\), \(\text {Ti}_{2}\text {IrAl}\), \(\text {Ti}_{2}\text {IrGa}\), and \(\text {Ti}_{2}\text {IrIn}\). The origin of half-metallicity was discussed for \(\text {Ti}_{2}\text {IrGa}\) using the energy band structure. The total magnetic moments of \(\text {Ti}_{2}\text {IrZ}\) (Z \(=\) B, Al, Ga, and In) compounds in \(\text {CuHg}_{2}\text {Ti}\)-type structure were obtained as \(2\mu _{\mathrm{B}}\) per formula unit, which were in agreement with Slater–Pauling rule (\(M_{\mathrm{tot}} =Z_{\mathrm{tot}}-\)18). All the four compounds were half-metals in a wide range of lattice constants indicating that they may be suitable and promising materials for future spintronic applications.

Half-metallicity in new Heusler alloys NaTO2 (T=Sc, Ti, V, Cr, and Mn): A first-principles study

On the basis of the full-potential linearized augmented plane wave (FPLAPW) method within density functional theory (DFT), electronic structure and magnetic properties of Heusler alloys NaTO2 (T = Sc, Ti, V, Cr, and Mn) were investigated. The negative values of formation energy showed that these compounds can be experimentally synthesized. Results showed that in all compounds, AlCu2Mn-type structure was the most favorable one. The NaTO2 (T = Sc, Ti, V, Cr, and Mn) alloys were HM ferromagnets except NaScO2 (in both structures which were nonmagnetic semiconductors) and NaVO2 (in AlCu2Mn-type structure which was a magnetic semiconductor). The origin of half-metallicity was also verified in HM alloys. NaCrO2 and NaVO2 alloys had higher half-metallic band gaps in comparison with Heusler alloys including and excluding transition metals. The total magnetic moments of HM NaTO2 (T = Ti, V, Cr, and Mn) alloys obeyed Slater-Pauling rule (Mtot = Ztot-12). Among NaTO2 (T = Sc, Ti, V, Cr, and Mn) alloys, NaCrO2 had the highest robustness of half-metallicity with variation of lattice constant in both structures.

Half-metallicity and magnetism of quaternary Heusler compounds CoRuTiZ (Z=Si, Ge, and Sn)

First-principle calculations based on the density functional theory for new quaternary Heusler compounds CoRuTiZ (Z=Si, Ge, and Sn) were performed. It was found that all three compounds were stable at YI structure in ferromagnetic state. The CoRuTiSi, CoRuTiGe, and CoRuTiSn were half-metal with integer magnetic moments of 1.00 μB per formula unit and half-metallic gaps of 0.13, 0.10, and 0.01eV at their equilibrium volume, respectively. The density of states (DOSs) and band structures of these compounds were studied and the origin of half-metallicity was discussed. The CoRuTiSi, CoRuTiGe, and CoRuTiSn compounds showed half-metallic characteristics at lattice constants ranges of 5.77–6.36Å, 5.66–6.16Å, and 5.83–6.23Å, indicating the lattice distortion did not affect the half-metallic properties of these compounds which makes them interesting materials in the spintronic field.

The electronic structure and half-metallic properties of zincblende TiBi (001) surfaces and TiBi(001)/InSb(001) interface

Abstract First principles calculations were performed using full potential linearized augmented plane wave (FPLAPW) method based on density functional theory (DFT) to study bulk TiBi in rock salt (RS), hexagonal NiAs, and zincblende (ZB) structures, free (001) surfaces of ZB TiBi, and interface of ZB TiBi with InSb(001). The nonmagnetic NiAs structure was ground state structure of bulk TiBi and nonmagnetic RS and ferromagnetic ZB structures were introduced as metastable structures. It was found that ZB TiBi is a half-metallic (HM) ferromagnet with a minority band gap of about 1.43 eV. The origin of half-metallicity was also discussed. The obtained phase diagram showed more stability of the Bi (001) terminated surface compared with the Ti (001) termination. The Ti (001) termination keeps HM property, while half-metallicity was destroyed at Bi (001) termination. The ZB TiBi/InSb (001) interface revealed HM property showing that InSb semiconductor is a suitable substrate for growing ZB TiBi in spintronics.

Nanoscale magnetism and novel electronic properties of a bilayer bismuth(111) film with vacancies and chemical doping.

Magnetically doped topological insulators (TIs) exhibit several exotic phenomena including the magnetoelectric effect and quantum anomalous Hall effect. However, from an experimental perspective, incorporation of spin moment into 3D TIs is still challenging. Thus, instead of 3D TIs, the 2D form of TIs may open up new opportunities to induce magnetism. Based on first principles calculations, we demonstrate a novel strategy to realize robust magnetism and exotic electronic properties in a 2D TI [bilayer Bi(111) film: abbreviated as Bi(111)]. We examine the magnetic and electronic properties of Bi(111) with defects such as bismuth monovacancies (MVs) and divacancies (DVs), and these defects decorated with 3d transition metals (TMs). It has been observed that the MV in Bi(111) can induce novel half metallicity with a net magnetic moment of 1 μB. The origin of half metallicity and magnetism in MV/Bi(111) is further explained by the passivation of the σ-dangling bonds near the defect site. Furthermore, in spite of the nonmagnetic nature of DVs, the TMs (V, Cr, Mn, and Fe) trapped at the 5/8/5 defect structure of DVs can not only yield a much higher spin moment than those trapped at the MVs but also display intriguing electronic properties such as metallic, semiconducting and spin gapless semiconducting properties. The predicted magnetic and electronic properties of TM/DV/Bi(111) systems are explained through density of states, spin density distribution and Bader charge analysis.

Electronic and Magnetic Properties of the Bulk and Surfaces of Rock salt KM (M = Se and Te): A Density Functional Theory Study

Electronic and magnetic properties of the bulk and different surfaces of KM (M = Se and Te) in rock salt structure (rs-KM) have been investigated. The results of our calculations show that these compounds are half-metallic ferromagnets with a magnetic moment of 1 μB. The origin of half-metallicity is also considered by plotting the partial densities of states (DOSs) and the spin-dependent band structures. The Curie temperatures of the samples are found to be 541 and 386 K for KSe and KTe, respectively. We also find that these compounds can preserve the half-metallicity up to high lattice compressions which means that they could be grown over several semiconductors. The results of the calculations show that the bulk half-metallicity is well preserved at all of the (001), (110), K-terminated (111), and M-terminated (111) surfaces. Using ab initio atomic thermodynamics, we calculate the surface energy as a function of chemical potential to find the most stable surface and we find that the K-terminated (111) surface is the most stable surface over the whole allowed range of the chemical potential.

Robust Half-Metallicity and Electronic Structure of the New Full-Heusler Compounds CsBaX2 (X = C, N, and O)

The electronic structure and magnetism of new Heusler alloys of CsBaX2 (X = C, N, and O) were investigated within density functional theory (DFT) using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method. The CsBaC2 in the AlCu2Mn-type was a half-metallic ferromagnet while it was a nonmagnetic metal in CuHg2Ti-type structure. CsBaN2 and CsBaO2 compounds in both structures were half-metallic ferromagnets. The majority band gap for CsBaC2 in the AlCu2Mn-type was obtained equal to 1.67 eV and for CsBaN2 and CsBaO2 compounds in the AlCu2Mn-type (CuHg2Ti-type) structure were calculated equal to 2.34 (2.29) eV and 3.53 (2.76) eV, respectively. The origin of half-metallicity was also studied using the band structure calculations and density of states (DOSs). The total magnetic moments of CsBaC2, CsBaN2, and CsBaO2 compounds were, respectively, obtained as 5 μ B , 3 μ B , and 1 μ B per formula unit at the equilibrium lattice parameter, which were in agreement with Slater-Pauling rule (M tot =12-Z tot). The CsBaX2 (X = C, N, and O) compounds kept their half-metallic characteristic in a wide range of lattice constants in comparison with Heusler alloys including transition metals, which makes them promising and attractive materials in spintronic field.

First principles study on half-metallic properties of Heusler compounds Ti2VZ (Z=Al, Ga, and In)

First principles calculations using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method in the framework of density functional theory (DFT) were performed to study the electronic structures and magnetic properties of new full-Heusler compounds Ti2VZ (Z=Al, Ga, and In). Electronic structure calculations showed that Ti2VZ (Z=Al, Ga, and In) compounds in AlCu2Mn-type are conventional ferrimagnets. The Ti2VAl, Ti2VGa, and Ti2VIn compounds in the CuHg2Ti-type structure have half-metallic characteristics with a respective majority band gap of 0.52, 0.51, and 0.59eV at the equilibrium lattice parameter. The origin of half-metallicity in these compounds was also discussed. The total magnetic moments of Ti2VZ (Z=Al, Ga, and In) compounds in the CuHg2Ti-type structures were 2μB per formula unit which were in agreement with Slater–Pauling rule (Mtot=18−Ztot). The Ti2VAl, Ti2VGa, and Ti2VIn compounds in the CuHg2Ti-type structure respectively showed half-metallic characteristics at lattice constants ranges of 6.12–7.17Å, 5.99–7.12Å, and 6.31–7.06Å, indicating the lattice distortion did not affect the half-metallic properties of these compounds which makes them interesting materials in the spintronics field.

Structural and phonon dynamical stability of the hypothetical RbN and CsN compounds

A first-principles approach is used to study the structural and dynamical stability of the hypothetical RbN and CsN compounds. First, I review briefly our earlier work on the origin of half-metallicity and then I present detailed results on the mechanical and dynamical properties obtained from the ultra soft pseudopotential approach. The elastic constants of both compounds in their equilibrium B2 phase confirm the mechanical stability. The phonon dispersions are calculated from the density functional perturbation theory and show no imaginary frequencies. Other thermodynamic properties are also obtained from the quasi-harmonic approximation and show good behavior with temperature.

The origin of half-metallicity in conjugated electron systems—a study on transition-metal-doped graphyne

We studied the mechanism of half-metallicity (HM) formation in transition-metal-doped conjugated carbon based structures by first-principles electronic structure simulations. It is found that the HM is a rather complex phenomenon, determined by the ligand field splitting of d-orbitals of the transition metal atoms, the exchange splitting and the number of valence electrons. Since most of the conjugated carbon based structures possess ligands with intermediate strength, the ordering of the d-orbital splitting is similar in all structures, and the HM properties evolve according to the number of valence electrons. Based on this insight we predict that Cr-, Fe- and Co-doped graphyne will show HM, while Mn- and Ni-doped graphyne will not. By tuning the number of valence electrons, we are thus able to control the emergence of HM and control the energy gaps evolving in the majority or minority spin channels.