The structural,half-metal,magnetic, and mechanical properties of full Heusler alloy CrCoVSb: A first-principles study

In this paper, the Co-mixing calculation of the full Heusler alloy Cr₂VSb was performed using a first-principles calculation method. The calculations revealed that, after mixing with Co, the Cr₂VSb alloy can form a full Heusler alloy that is a half-metallic magnetic material with an equilibrium lattice parameter of 6.059 Å. Furthermore, the results showed that the magnetic properties of this alloy are mainly derived from the contributions of d electrons associated with the Cr, Co, and V atoms. Stress-induced changes in the lattice parameter had a significant influence on the magnetic moment of each atom, but, owing to mutual compensation, the total magnetic moment of the alloy remained unchanged. In terms of mechanical properties, the results revealed that the CrCoVSb alloy is an anisotropic ductile material.     

Phase diagrams,electronic and magnetic properties of the quaternary Heusler alloy NbRhCrAl

In this paper, we are studying the quaternary Heusler alloy NbRhCrAl, using the full potential linearized augmented plane wave and the generalized gradient approximation of the exchange and correlation potential methods. For this purpose, we established the electronic and magnetic properties of this quaternary Heusler alloy. We investigated the density of states (DOS) and the band structure of this Heusler compound.This material contains three magnetic atoms: Nb, Rh and Cr modeled by the spin moments S = 1, P = 5/2 and Q = 3/2, respectively. In a first step, we elaborated the ground state phase diagrams in different physical parameter planes to explore the existing stable configurations. On the other hand, we used the MONTE CARLO simulations (MCS) to investigate the thermal behavior of the magnetizations of this system. Also, we have investigated the effect of varying the crystal field and the external magnetic field on the total magnetizations. To complete this study, we illustrated and discussed the hysteresis loops as a function of the external magnetic field, when fixing the values of the studied physical parameters.     

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.     

铁基Heusler合金Fe2Co1-xCrxSi的结构、磁性和输运性质的研究

基于多种实验手段和能带计算的方法, 对四元合金Fe₂Co_1-xCr_xSi的晶体结构、 磁性、输运性质及能带结构进行了研究. 研究发现, 随着Cr的增加, 合金Fe₂Co_1-xCr_xSi保持了高度有序结构, 逐渐从Hg₂CuTi结构的Fe₂CoSi 过渡到L2₁结构的Fe₂CrSi; 由于次晶格网络的破坏, 居里温度逐渐下降; 系列合金的分子磁矩呈现线性下降, 符合半金属特性; 剩余电阻比率与原子占位有序程度密切相关, 呈现两端大、 中间小的特点. 在Cr替代Co的过程中, 材料半金属能隙逐渐打开, 表现半金属特征. 同时费米能级从Fe₂CoSi半金属能隙的价带顶上移至Fe₂CrSi能隙的导带底. 最大的能隙宽度出现在x= 0.75处, 这表明四元合金有可能成为具有更高自旋极化率和更强抗干扰能力的自旋电子学材料.     

Half-metallicity and spin transport studies on quaternary CoCuMnSb Heusler alloy

Herein, the crystalline structure and spin transport properties of CoCuMnSb (CCMS) half-metallic Heusler alloy have been investigated with ab-initio calculations and nonequilibrium Green's function. Experimental and theoretical results reveal that CCMS alloy stabilizes in a highly ordered LiMgPdSn-type structure with lattice parameters of a = 6.113 Å and α = 90°, which match well with the reported lattice parameters of GaSb. Furthermore, the theoretical calculations indicate that CCMS exhibits perfect polarized spin at the Fermi level. Therefore, we have designed CCMS/GaSb heterostructure and CCMS/GaSb/CCMS magnetic tunnel junction (MTJ). Our architecture exhibits effective spin filtering and the MTJ produces a dramatic magnetoresistance ratio (~445). These outstanding properties marks CCMS as a strong system for applications in spintronics.     

Half-metallic properties of the CuHg2Ti-type Mn2ZnSi full-Heusler compound

The half-metallic properties of novel CuHg₂Ti-type Mn₂ZnSi full-Heusler compound were examined by density functional theory (DFT) calculations. The electronic band structures and density of states of the Mn₂ZnSi compound show that spin-up electrons are metallic, but the spin-down bands are semiconductor with a gap of 0.48 eV, and the spin-flip gap is of 0.28 eV. The Mn₂ZnSi Heusler compound has a magnetic moment of 2 μ_B at the equilibrium lattice constant a = 5.80 Å. The Mn₂ZnSi full-Heusler compound is ferrimagnetic and maintains the half-metallic character having 100% polarization for lattice constants ranging between 5.62 and 6.91 Å.     

Ab Initio Study of the Magnetism and Half-Metallic Properties of d0 Quaternary Heusler Alloys BaNYO (Y = K,Rb, and Cs)

JETP Letters - An ab initio theory has been applied to investigate the electronic, elastic, magnetic, and half-metallic behaviors of the newly designed quaternary Heusler compounds BaNYO (Y = K,...     

Electronic,magnetic and Fermi properties investigates on quaternary Heusler NiCoCrAl,NiCoCrGa and NiFeCrGa

Using the full-potential local-orbital minimum-basis method within the framework of density functional theory, we study the electronic, magnetic and Fermi properties of three quaternary Heusler compounds: NiCoCrAl, NiCoCrGa and NiFeCrGa. Results identify that these compounds are half-metallic ferromagnets with integer spin magnetic moment, and their spin moments follow the Slater–Pauling rule. Accordingly, the origin of gap and magnetic moment are also discussed. In addition, the Fermi surface is further plotted to explore the behavior of electronic states in the vicinity of Fermi level for these compounds. Finally, we argue the influence of tetragonal deformation on electronic and magnetic properties. Meanwhile, the possible L2₁ disorder is also discussed for NiCoCrAl and NiCoCrGa.     

Electronic structure and half-metallicity of the new Heusler alloys PtZrTiAl,PdZrTiAl and Pt0.5Pd0.5ZrTiAl

The electronic structure and magnetic properties of the PtZrTiAl, PdZrTiAl and Pt_0.5Pd_0.5ZrTiAl Heusler alloys were investigated using the full-potential linearized augmented plane wave (FPLAPW) within the generalized gradient approximation (GGA). For the PtZrTiAl, and PdZrTiAl alloys, the results showed that these Heusler alloys were stable in the Type I structure. The (Pt, Pd)ZrTiAl Heusler alloys are found to exhibit half-metallic ferromagnetism for both the Type I and Type II structure. The total magnetic moments of the PtZrTiAl and PdZrTiAl alloys were obtained to be 3 μ_B per formula unit, which are in agreement with the Slater-Pauling rule m_tot = (Nv ? 18). The half-metalliciy characteristic exists in the relatively wide ranges of 6.06–6.78 Å, and 6.13–6.73 Å for the PtZrTiAl and PdZrTiAl alloys, respectively. To complete the fundamental characteristics of these alloys, Pt_0.5Pd_0.5ZrTiAl is predicted to be a half-metallic ferromagnet with an energy gap of 0.90 eV in the minority spin and a complete spin polarization at the Fermi level. These new Heusler alloys may become ideal candidate material for future spintronic applications.     

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 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.     

Band structure calculations for Heusler phase Co2YBi and half-Heusler phase CoYBi (Y=Mn, Cr)

We have studied the electron structure and magnetic properties of Heusler phase Co₂YBi and half-Heusler phase CoYBi (Y=Mn, Cr) by using the full-potential linearized-augmented plane-wave (FLAPW) method. Co₂MnBi and Co₂CrBi are predicted to be half-metallic magnetism with a total magnetic moment of 6 and 5 μ_B, respectively, well consistent with the Slater-Pauling rule. We also predict CoMnBi to be half-metallic magnetism with a slight compression. The gap origin for Co₂MnBi and Co₂CrBi is due to the 3d electron splitting of Mn (Cr) and Co atoms, and the gap width depends on Co electron splitting. The atom coordination surroundings have a great influence on the electron structure, and consequently the Y site in the X₂YZ structure has a more remarkable electron splitting than the X site due to the more symmetric surroundings. The investigation regarding the lattice constant dependence of magnetic moment shows that the Co magnetic moment exhibits an opposite behavior with the change of the lattice constant for Heusler and half-Heusler alloys, consequently leading to the different variation trends for total magnetic moment. The variation of total and atom magnetic moment versus lattice constant can be explained by the extent of 3d electron splitting and localization of Mn (Cr) and Co atoms for both the series of alloys.     

第一性原理研究semi-Heusler合金CoCrTe和CoCrSb的半金属性和磁性

采用第一性原理的全势能线性缀加平面波方法,对semi-Heusler合金CoCrTe和CoCrSb的电子结构进行自旋极化计算.CoCrTe和CoCrSb处于平衡晶格常数时是半金属性铁磁体,其半金属隙分别为0.28和0.22 eV,晶胞总磁矩为3.00μB和2.00μB.CoCrTe和CoCrSb的晶胞总磁矩主要来自于Cr原子磁矩.Co,Te和Sb的原子磁矩较小,它们的磁矩方向与Cr原子的磁矩方向相反.使晶格常数在±13%的范围内变化(相对于平衡晶格常数),并计算CoCrTe和CoCrSb的电子结构.计算研究表明,CoCrTe和CoCrSb的晶格常数变化分别在-11.4%—9.0%和-11.2%—2.0%时仍具有半金属性,并且它们晶胞总磁矩稳定于3.00μB和2.00μB.     

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.     

Half-metallic ferrimagnetism in Full-Heusler alloy Mn2CuMg

In the paper Ab initio electronic structure calculations are applied to study the electronic structure and magnetism properties of a new Mn-based Heusler alloy Mn₂CuMg. We take into account both possible L 2₁ structures (CuHg₂Ti and AlCu₂Mn types). The CuHg₂Ti-type structure is found to be energetically more favorable than the AlCu₂Mn-type structure and presents half-metallic ferrimagnetism. However, the case of exchanging X with Y atoms in generic formula loses its half-metallicity due to the symmetric surroundings. Calculations show that their total spin moment is −1μ_B for a wide range of equilibrium lattice constants and the total spin magnetic moment is attributed mainly to the two Mn atoms, while the Cu atom is almost non-magnetic. A small total spin moment origins from the antiparallel configurations of the Mn partial moments. The CuHg₂Ti-type Mn₂CuMg alloy keeps a 100% of spin polarization of conduction electrons at the Fermi level, thus opening the way to engineer new half-metallic alloys with the desired magnetic properties.     

Spin-dependent thermoelectric effect in Co2Fe0.4Mn0.6Si thin film with perpendicular magnetic anisotropy

We report the anomalous Nernst effect in trilayers containing a thin film of the half-metallic ferromagnetic Heusler alloy Co₂Fe_0.4Mn_0.6Si with perpendicular magnetic anisotropy. The structure is MgO/CFMS/Pd and we have studied the variation of anomalous Hall and Nernst effects as a function of CFMS and Pd thickness. The anomalous Nernst coefficient reaches 0.5 μV/K at room temperature and we have observed a strong dependence of the anomalous Nernst coefficient on the thickness of both layers. Our results indicate that inducing perpendicular magnetic anisotropy in a strongly spin-polarising Heusler alloy such as CFMS is very promising for new thermoelectric devices based on exploiting the anomalous Nernst effect.     

The spin effect in zinc-blende CdEuS and CdEuSe: GGA and GGA+U studies

We have investigated the structural, electronic and magnetic properties of substitutional europium rare earth impurity in cubic CdS and CdSe by employing the ab-initio method. Calculations were performed by using the full potential linearized augmented plane wave plus local orbitals (FP-L/APW+lo) method within the framework of spin-polarized density functional theory (DFT). The electronic exchange-correlation energy is described by generalized gradient approximation GGA and GGA+U (U is the Hubbard correction). The GGA+U method is applied to the rare-earth 4f states. We have calculated the lattice parameters, bulk modulii, the first pressure derivatives of the bulk modulii and the cohesive energies. The calculated densities of states presented in this study identify the metallic behavior of CdEuS and CdEuSe when we use the GGA scheme, whereas when we use the GGA+U, we see that these compounds are half-metallic.     

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.     

Electronic band structure matching for half- and full-Heusler alloys

We explore the lattice and the electronic band structures matching between the half-metallic Heusler alloys (half-Heusler NiMnSb and full-Heusler Co₂MnSi) and several hypothetical non-magnetic Heusler alloys by using first principle calculations. The lattice and band structure matching are almost perfectly satisfied between the two materials of similar crystal structures: (i) NiMnSb and XYSb and (ii) Co₂MnSi and X₂YSi, where X, Y=Ni or Cu. Owing to the high interface spin scattering asymmetry, these materials are promising to realize a high giant magnetoresistance at room temperature.     

First principles study of half-metallic ferromagnetism in Cr-doped CdTe

We report a systematic study of the structural, electronic and magnetic properties of Cr-doped CdTe for various Cr concentrations x (=0.25, 0.5, 0.75 and 1.0) using first principles calculations based on the density functional theory (DFT). The electronic band structure of the alloy has been calculated using the Wu-Cohen (WC) as well as the Angel-Vosko (EV) generalized gradient approximation (GGA) for the exchange-correlation potential. The analysis of the density of states (DOS) curves shows the half-metallic ferromagnetic character with half-metallic gap more than 0.52 eV. While the origin of half-metallic ferromagnetism is explained, the band structure calculations are used to determine s (p)-d exchange constants N₀α (conduction band) and N₀β (valence band) that agree with typical magneto-optical experiment. It is found that the p-d hybridization reduces the magnetic moment of Cr from its free space charge value and produces small magnetic moments on the Cd and Te sites. Lastly, we discuss the robustness of half-metallicity with respect to the variation of lattice constants of the Cr_xCd_1−xTe alloys.