Magnetism in the new full-Heusler compound,Zr2CoAl: A first-principles study

The electronic structure and magnetic properties of Zr₂CoAl bulk material were investigated within the Density Functional Theory (DFT) framework. The material, basically a complete spin polarized half-metallic ferromagnet in the ground state, crystallizes in the ordered full-Heusler inverse structure (Hg₂CuTi-type structure). The energy band gap, localized in minority spin channel is 0.48 eV at equilibrium lattice parameter, 6.54 Å. The total magnetic moment calculated, equal to 2 μ_B/f.u., is an integral, in agreement with the Slater-Pauling curve for full-Heusler alloys.     

Half-metallic properties of Ti2FeSi full-Heusler compound

In this study, the electronic structure and magnetic properties of novel half-metallic Ti₂FeSi full-Heusler compound with CuHg₂Ti-type structure were examined by density functional theory (DFT) calculations. The electronic band structures and density of states of the Ti₂FeSi compound show the spin-up electrons are metallic, but the spin-down bands are semiconductor with a gap of 0.45 eV, and the spin-flip gap is of 0.43 eV. Fe atom shows only a small magnetic moment and its magnetic moment is antiparallel to that of Ti atoms, which is indicative of ferrimagnetism in Ti₂FeSi compound. The Ti₂FeSi Heusler compound has a magnetic moment of 2 μ_B at the equilibrium lattice constant a=5.997 Å.     

A first principles study on the full-Heusler compound Mn2CuSi

Using a state-of-the-art full-potential electronic structure method within the generalized gradient approximation (GGA), we study the electronic structure and magnetic properties of the Mn₂CuSi full-Heusler alloy. Calculations show that CuHg₂Ti-type structure alloy is a half-metallic ferrimagnet with the Fermi level (ε_F) being located within a tiny gap of the minority-spin density of states. The conduction electron at ε_F keeps a 100% spin polarization. A total spin moment, which is mainly due to the antiparallel configurations of the Mn partial moments, is −1.00μ_B for a wide range of equilibrium lattice parameters. Simultaneously, the small spin magnetic moments of Cu and Si atoms are antiparallel. The gap mainly originates from the hybridization of the d states of the two Mn atoms. Thus, Mn₂CuSi may be the compound of choice for further experimental investigations.     

First-principles study of half-metallic properties of the Heusler alloy Ti2CoGe

First-principles calculations have been performed on the electronic structures and magnetic properties of a new Ti₂Co-based full-Heusler alloy Ti₂CoGe. The calculations predict the Ti₂CoGe is a half-metallic ferromagnet at the equilibrium lattice constant with the minority-spin energy gap of 0.60 eV. It is found that the total magnetic moment (M_t) and the number of valence electrons (Z_t) in Ti₂CoGe obey a new Slater–Pauling (SP) rule of M_t=Z_t−18 and the rule also can be applied to other Ti₂Co-based half-metallic full-Heusler alloys. The Ti₂CoGe alloy keeps a 100% polarization at Fermi level and maintains the half-metallic character for lattice constants ranging between 6.05 and 6.67 Å.     

First-principle calculations of structural,electronic and magnetic investigations of Mn2RuGe1-xSnx quaternary Heusler alloys

First-principles calculations were used to calculate the structural, electronic and half-metallic ferromagnetism of Mn₂RuGe_1-xSn_x (x?=?0, 0.25, 0.50, 0.75, 1) Heusler alloys. The Hg₂CuTi-type structure is found to be energetic more than Cu₂MnAl-type structure for both Mn₂RuGe and Mn₂RuSn compounds. The calculated lattice constants for Mn₂RuGe and Mn₂RuSn are 5.91?Å and 6.17?Å, respectively. The electronic band structures and density of states of Mn₂RuGe show a half metallic character with total magnetic moments, 2 μ_B per formula unit that are in good agreement with Slater-Pauling rule with indirect band gap, 0.31?eV along the direction Γ –X. It is observed that the total magnetic moment per cell increases as Sn concentration increases in the Heusler alloys.     

A better ferrimagnetic half-metal LuCu3Mn4O12: Predicted from first-principles investigation

Electronic structure calculations based on density functional theory (DFT) within the generalized gradient approximation (GGA) and GGA+U for manganite cuprate compound LuCu₃Mn₄O₁₂ have been performed, using the full-potential linearized augmented plane wave method. The calculated results indicate that LuCu₃Mn₄O₁₂ is ferrimagnetic and half-metallic in both GGA and GGA+U calculations. The minority-spin band gap is 0.7 eV within GGA, which is larger than that of LaCu₃Mn₄O₁₂ (0.3 eV), indicating its better half-metallicity. Further, the minority-spin gap enlarges from 0.7 to 2.8 eV with U taken into account, and simultaneously the Fermi level being shifted to the middle of the gap, making the half-metallic energy gap to be 1.21 eV. These results demonstrate that electronic correlation effect enhances the stability of half-metallic property. These facts make this system interesting candidates for applications in spintronic devices.     

Half-metallicity in the full-Heusler Co2ScP compound: A density functional study

The electronic structure and magnetic properties of the Heusler compound Co₂ScP have been investigated by the generalized gradient approximation based on density functional theory. The results show that the ground state phase of the Co₂ScP compound possesses AlCu₂Mn-type crystal structure and exhibits half-metallic ferrimagnetism. The total spin moment is 2 μ_B at the equilibrium lattice constant a₀=5.83 Å, which agrees with the Slater–Pauling rule. The spin-up electrons are metallic, but the spin-down bands are semiconductor with a gap of 0.55 eV, and the spin-flip gap is of 0.07 eV.     

Half-metallic ferrimagnetism in the Ti2CoAl Heusler compound

Density functional calculations performed on the Ti₂CoAl Heusler compound confirm it to be a half-metallic ferrimagnet with the spin-down energy gap of 0.49 eV. The Ti₂CoAl Heusler compound has a magnetic moment of 2 μ_B at the equilibrium lattice constant a=6.14 Å. The Ti₂CoAl Heusler compound is ferrimagnetic and maintains the half-metallic character having 100% polarization for lattice constants ranging between 5.85 and 6.44 Å.     

First-principle study of the electronic,magnetic and structural characteristics of the Mn2CoAs1−xAlx (x = 0,0.25,0.50,0.75) Heusler alloys

First-principles density functional theory approach is adopted to determine the electronic, magnetic and structural characteristics of the Mn₂CoAs_1−xAl_x (x = 0,0.25,0.50,0.75) Heusler alloys. The computations are carried out by WIEN2k code based on full-potential linearized augmented plane wave method (FP-LAPW). Moreover, the exchange-correlation energy functional is treated at the level of the generalized gradient approximation (GGA). Analysis of our computed results of the electronic band structure, as well as the density of states of the Mn₂CoAs compound, show it a stable and half-metallic material with an energy band gap value of 0.48 eV. The calculated spin gap values are: 0.627 eV, 0.22 eV and 0.188 eV for Mn₂CoAs_0.75Al_0.25, Mn₂CoAs_0.50Al_0.50 and Mn₂CoAs_0.25Al_0.75 respectively. Furthermore, the calculated total magnetic moment of the Mn₂CoAs (4 µB) is found to be in agreement with the Slater–Pauling rule. Thus, our calculations show the Mn₂CoAs_1−xAl_x (x = 0, 0.25, 0.50, 0.75) Heusler alloys potential materials for near future applications in spintronic because of their half-metallic ferromagnetism property.     

Electronic structure and magnetism in full-Heusler compound Mn2ZnGe

The first-principle calculations within density functional theory are used to investigate the electronic structure and magnetism of the Mn₂ZnGe Heusler alloy with CuHg₂Ti-type structure. The half-metallic ferrimagnets (HMFs) in Mn₂ZnGe are predicted. The energy gap lies in the minority-spin band for the Mn₂ZnGe alloy. The calculated total spin magnetic moment is −2μ_B per unit cell for Mn₂ZnGe alloy, the magnetic moments of Zn and Mn(B) are antiparallel to that of Mn(A), and we also found that the half-metallic properties of Mn₂ZnGe are insensitive to the dependence of lattice within the wide range of 5.69 and 5.80 Å where exhibiting perfect 100% spin polarization at the Fermi energy.     

Spintronic properties of the Ti2CoB Heusler compound by density functional theory

The electronic structure and magnetic properties of the Ti₂CoB Heusler compound with a high-ordered CuHg₂Ti structure were investigated using the self-consistent full potential linearized augmented plane wave (FPLAPW) method within the density functional theory (DFT). Spin-polarized calculations show that the Ti₂CoB compound is half-metallic ferromagnetic with a magnetic moment of 2 μ_B at the equilibrium lattice constant, a=5.74 Å. The Ti₂CoB Heusler compound is ferromagnetic below the equilibrium lattice constant and ferrimagnetic above the equilibrium lattice constant. A large peak in majority-spin DOS and an energy gap in minority-spin DOS are observed at the Fermi level, yielding a spin polarization of 100%. A spin polarization higher than 90% is achieved for a wide range of lattice constants between 5.6 and 6.0 Å.     

Pressure and disorder effects on the half-metallic character and magnetic properties of the full-Heusler alloy Co2FeSi

We investigate the pressure and site disorder effects on the half-metallicity and magnetic properties of the full-Heusler alloy Co₂FeSi using first-principles density functional theory within the GGA and GGA+U schemes. The calculated lattice constant, bulk modulus and total magnetic moments are in excellent agreement with recent experiments. The volume compression leads to a slight increase of the minority band gap, i.e., the half-metallic properties of Co₂FeSi can maintain under pressure. The disorder calculations reveal that Fe–Co type disorder significantly destroys the half-metallic character and reduces the spin polarization of Co₂FeSi while disorder between Fe and Si can maintain half-metallic properties. Our results also show that the Fe–Co type disorder leads to degradation of the magnetism while the Fe–Si type disorder affects hardly the magnetism as observed in Co₂FeSi.     

Defects-driven appearance of half-metallic ferrimagnetism in Co-Mn-based Heusler alloys

Half-metallic ferromagnetic full-Heusler alloys containing Co and Mn, having the formula Co₂MnZ where Z is a sp element, are among the most studied Heusler alloys due to their stable ferromagnetism and the high Curie temperatures which they present. Using state-of-the-art electronic structure calculations we show that when Mn atoms migrate to sites occupied in the perfect alloys by Co, these Mn atoms have spin moments antiparallel to the other transition metal atoms. The ferrimagnetic compounds, which result from this procedure, keep the half-metallic character of the parent compounds and the large exchange-splitting of the Mn impurities atoms only marginally affects the width of the gap in the minority-spin band. The case of [Co_1−xMn_x]₂MnSi is of particular interest since Mn₃Si is known to crystallize in the Heusler L2₁ lattice structure of Co₂MnZ compounds. Robust half-metallic ferrimagnets are highly desirable for realistic applications since they lead to smaller energy losses due to the lower external magnetic fields created with respect to their ferromagnetic counterparts.     

First-principles study of properties of Mn2ZnMg alloy

We investigate the electronic structures and magnetic properties of Mn₂ZnMg compound with Hg₂CuTi-type structure using first-principles full-potential local orbital minimum basis calculations. Based on the analysis on the electronic structures, it is demonstrated that the compound is half-metallic antiferromagnet and the compound is favorable to form Hg₂CuTi-type structure instead of the conventional L2₁ one. The complicated hybridization among the p and d states dominates mainly the origin of the gap. The Fermi level (E_F) shifts slightly with the lattice parameter changed. Spin-orbit coupling hardly reduces the degree of spin polarization of the density of states at the Fermi level.     

Experimental and theoretical studies on bis(glycine) lithium nitrate (BGLiN): A physico-chemical approach

Good quality and bulk size single crystal (size: 20×13×8 mm³) of bis(glycine) lithium nitrate (BGLiN) was grown by a slow evaporation solution technique from the aqueous solutions at constant temperature i.e. 27 °C using synthesized materials. Crystal system and lattice parameters were determined by single crystals as well as powder X-ray diffraction analysis. The lattice parameters of the titled compound are a=10.0223 Å, b=5.0343 Å, c=17.0510 Å, and V=860.312 Å³ and it crystallized in an orthorhombic system with space group Pca2₁ obtained by single crystal XRD. Elemental composition was confirmed by energy dispersive X-ray spectroscopic analysis. Optical absorption spectrum was recorded and various optical parameters such as optical transmission (~60%), and optical band gap (4.998 eV) were calculated. Photoluminescence study shows that the grown crystal is free from major defects. Crystalline perfection of the grown crystal was assessed and found good. Ground state optimized geometry has been obtained by using DFT with 6-31G(d,p) basis set. HOMO and LUMO energy gap was found to be 6.01 eV and dipole moment was 1.65 D.     

A first-principle study of half-metallic ferrimagnetism in the Ti2CoGa Heusler compound

Electronic structure calculations based on density functional (DFT) theory within the generalized gradient approximation (GGA) for the Ti₂CoGa Heusler compound have been performed using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method. The electronic band structures and density of states of the Ti₂CoGa compound show that the spin-up electrons are metallic, but the spin-down bands have a gap of 0.5 eV, resulting in stable half-metallic ferrimagnetic behavior with a magnetic moment of 2μ_B.     

Structural,electronic, magnetic and thermoelectric properties of inverse Heusler alloys Ti2CoSi,Mn2CoAl and Cr2ZnSi by employing Ab initio calculations

ABSTRACT

The inverse Heusler alloys such as Ti₂CoSi, Mn₂CoAl and Cr₂ZnSi were studied in the framework of density functional theory using FP-LAPW linearised augmented plane wave method in order to determine the different physical properties such as structural, electronic, magnetic and thermoelectric. The generalised gradient approximation (GGA) was used to treat the exchange–correlation energy and the Beck-Johnson (mBJ) approach was used to calculate the electronic properties. In all studied compounds, the stable type Hg₂CuTi was energetically more favourable than Cu₂MnAl type structure. The results show that two compounds (Ti₂CoSi and Mn₂CoAl) are both ferromagnetic (FM) while Cr₂ZnSi is antiferromagnetic (AFM). The compounds Ti₂CoSi and Mn₂CoAl have a total magnetic moment of 3 and 2?μ_B, respectively, whereas the Cr₂ZnSi alloy has a total magnetic moment equals zero. The Ti₂CoSi, Mn₂CoAl and Cr₂ZnSi compounds exhibit half-metallic (HM) character with 100% spin polarisation at the Fermi level. Finally, the semi-classical Boltzmann theory implicit in the BoltzTraP code was used to calculate the electronic transport coefficients such as thermal and electrical conductivity, the Seebeck coefficient and the factor of merit.     

Half-metallicity and magnetic properties of half-Heusler type Mn2Sn: Ab initio predictions

Ab initio calculations have been carried out to investigate the electronic structure and magnetism of the compound Mn₂Sn with the bcc half-Heusler structure. For the equilibrium lattice parameter 5.69 Å, Mn₂Sn is predicted to be a half-metallic fully compensated ferrimagnet (also called half-metallic antiferromagnet) with zero total spin moment. This zero moment agrees well with the Slater-Pauling curve and mainly comes from the compensated Mn (A) and Mn (B) spin moments in antiparallel configuration. The half-metallicity of Mn₂Sn is stable in a wide lattice-parameter range from 5.6 Å to 5.9 Å. Upon contraction of the lattice, a transition from half-metallicity to semimetallicity is observed.     

Structural and optoelectronic properties of Mg substituted ZTe (Z=Zn,Cd and Hg)

Wide band gap semiconductor alloys, Mg_xZ_1−xTe (Z=Zn, Cd and Hg), are investigated over a full range of Mg compositions (0≤x≤1) using density functional theory (DFT). The variation in the lattice constant of Mg_xZ_1−xTe is linear with the composition x, and all these alloys obey Vegrd's law. The CdTe (6.50 Å) and MgTe (6.44 Å) are lattice matched compounds, therefore the lattice constant of MgCdTe decreases slightly with the concentration x, whereas the lattice constant also decreases for MgHgTe but increases for MgZnTe. It is due to the fact that Mg has larger size than Zn and smaller size than Cd and Hg. The band gap of these compounds are calculated using the modified Becke–Johnson (mBJ) exchange potential as LDA and GGA are not effective in producing the experimental band gap of a strongly correlated electron system. The calculated band gaps of these compounds cover the range 0–3.5 eV and are consistent with the experimental band gaps. The band gaps exhibit nonlinear behavior or bowing effect with the change in concentration. The frequency dependent optical properties like dielectric functions, and indices of refraction of these ternary systems are also calculated and discussed.     

Investigation of structural,half-metallic and elastic properties of a new full-Heusler compound–Ir2MnSi

The electronic structure, magnetic and elastic properties of Ir₂MnSi full-Heusler compound is studied within the framework of Density Functional Theory (DFT). The ferromagnetic (FM) and non-magnetic (NM) states are compared in Cu₂MnAl and Hg₂CuTi prototype structures. The ferromagnetic state in Cu₂MnAl structure has been found energetically more stable than non-magnetic state in these two types of structures. Due to this stability, all calculations are carried out for FM-state. The spin-polarized calculations show that the spin-up electrons of Ir₂MnSi compound have metallic nature, but the spin-down electrons have semiconducting behavior with 0.55 eV energy gap around the Fermi level. The calculated Cauchy pressure and Poisson's ratio indicated that Ir₂MnSi compound is a ductile material. Ir₂MnSi compound is a half-metallic ferromagnet (HMF) and it has 5µ_B magnetic moment. This study will theoretically lead to experimental works in the spintronic field and its applications.