Value Of Total Magnetic Moment Research Articles

DFT insights on the Be1-xCrxS alloys for optoelectronic and magnetic devices

In this work, the electro-optical and magnetic characteristics of Be1-xCrxS (x= 6.25%, 12.5% and 25%) are brought into investigation by employing full potential linearized augmented plane wave (FP-LAPW) scheme designed within density functional theory (DFT). The stability of the Be1-xCrxS alloy is justified by the negative values of formation energy. The band structures and density of states are examined by using GGA functional. Be1-xCrxS compound demonstrates the half-metallic (HM) ferromagnetic behavior for all doping concentrations; spin-up channel reveals the metallic character and other spin version displays the semiconductor (SC) behavior. The values of total magnetic moment (µB) are recorded as 4.0 8.0 and 16.0 µB for corresponding 6.25%, 12.5% and 25%, which mainly arises owing to Cr-3d state. Moreover, optical features including dielectric function ε(ꞷ), reflectivity, refraction, and absorption are explored within range of 0-10 eV. The maximum absorption of incident photons was found in ultraviolet (UV) span which implies their importance for optoelectronic applications. Results reveal that the studied alloy has potential applications in magnetic and optoelectronic gadgets.

Study of ferromagnetism, and thermoelectric behavior of double perovskites K2Z(Cl/Br)6 (Z = Ta, W, Re) for spintronic, and energy application

Spintronic is the developing technology which probes the properties of quantum devices with spin of electrons which reduce the size and enhance its speed. Therefore, here the role of 5d electrons and thermoelectric characteristics of double perovskites (DPs) K2ZCl/Br6 (Z = Ta, W, Re) elaborated comprehensively by density functional theory (DFT). The Heisenberg model spin polarization density (SP) has been applied to evaluate the Curie temperature (Tc) and spin polarization factor. The tolerance factor (tF) and formation energy (ΔH) have been calculated to confirm the stability of structures. Ferromagnetism has been discussed in terms of spin polarization, crystal field energy (ΔCF) and exchange energies (Δ(d), Δ(pd)). The double exchange mechanism, and exchange constants ensure the role of electrons spin in ferromagnetism instead of segregation of transition metal ions. The transferring of magnetic moments of transitions metals to nonmagnetic sites (K, Cl, Br) show the exchange of spin of electrons and integer values of total magnetic moment show 100 % spin polarization. Finally, the transport properties are studied in standings of electrical and thermal conductivities. The large value of Seebeck coefficient and power factor ensure the importance of studied DPs for thermoelectric generators.

Investigation on the physical properties of Ni doped SrTiO3 by first-principle calculations

In present work, the magneto-electronic and optical features of Sr1-xNixTiO3 (x = 12.5%, 25%, 50% and 75%) compounds are calculated using full potential linearized augmented plane wave (FP-LAPW) scheme within density functional theory (DFT) as employed in WIEN2k software. The electronic band structures (BS) and density of states (DOS) interpret the induced half metallic ferromagnetism mainly originating from highly spin polarized Ni-d states. The computed value of total magnetic moment of Sr1-xNixTiO3 is 1.99998, 1.99991, 2.00003 and 2.00005 µB at 12.5%, 25%, 50% and 75% concentration respectively, which emerge primarily due to Ni-3d electrons. Furthermore, the optical features (refraction, dielectric function, absorption, and reflectivity) have also been computed within energy range of 0-10 eV. Sr1-xNixTiO3 is optically active in visible to ultraviolet (UV) region owing to low reflectivity and high absorption. Results portray that the studied compound is a potential contender for its usage in the development of spintronic and optoelectronic devices.

Phase stability and physical property for off-stoichiometric Ni-Mn-Sb alloys including 4O phase

Large magnetic field-induced strains can only be found in modulated martensite for Ni-Mn-Sb alloys, but the theoretical research on this alloy which is generally concentrated in the austenite and non-modulated martensite (NM) ignores the modulated martensite. Therefore, in this paper, we systematically study the relationship between phase stability, physical property and composition in the full series Ni-Mn-Sb Heusler alloys (Ni24+xMn12-xSb12, Ni24+xMn12Sb12-x, Ni24-xMn12+xSb12, Ni24Mn12+xSb12-x) including four-layered orthorhombic modulated martensite (4O) by the first principles calculations. For phase stability, we determined that the critical components of 4O for Ni24+xMn12-xSb12, Ni24+xMn12Sb12-x and Ni24Mn12+xSb12-x is × = 6, x = 6 and × = 4, respectively. There is no 4O phase within the concentration range considered for Ni24-xMn12+xSb12. Moreover, the martensitic transformation sequences are also determined. As for physical properties, the transformation temperatures from austenite to 4O and NM phases are predicted respectively. Meanwhile, the ternary magnetic moment diagram of austenite, 4O and NM phases is constructed. The maximum value of total magnetic moment is distributed in the Ni-excess Sb-deficient system, while the minimum value of that is distributed in the Mn-excess Sb-deficient system. The origin of the above observations is explained by the competition between the Jahn-Teller effect in the electronic structure and the strength of the covalent bond. The results in this paper are expected to provide information for the composition design and performance optimization of Ni-Mn-Sb alloy.

Large ordered moment with strong easy-plane anisotropy and vortex-domain pattern in the kagome ferromagnet Fe3Sn

We report the magnetic anisotropy of kagome bilayer ferromagnet Fe3Sn probed by the bulk magnetometry and magnetic force microscopy (MFM) on high-quality single crystals. The dependence of magnetization on the orientation of the external magnetic field reveals strong easy-plane magnetocrystalline anisotropy and anisotropy of the saturation magnetization. The leading magnetocrystalline anisotropy constant shows a monotonous increase from K1≈−1.0×106 J/m3 at 300 K to −1.3×106 J/m3 at 2 K. Our ab initio electronic structure calculations yield the value of total magnetic moment of 7.1 μB/f.u. and a magnetocrystalline anisotropy energy density of −0.57 meV/f.u. (−1.62×106J/m3) both being in reasonable agreement with the experimental values. The MFM imaging reveals micrometer-scale magnetic vortices with weakly pinned cores that vanish at the saturation field of ∼3 T applied perpendicular to the kagome plane. The observed vortex-domain structure is well reproduced by the micromagnetic simulations, using the experimentally determined value of the anisotropy and exchange stiffness.

High Curie temperature and half-metallic ferromagnetism in Cr- and V-doped ZnSe in wurtzite phase: First-principles study

The electronic and magnetic properties of Cr-, V-doped, and co-doped ZnSe in the wurtzite structure have been calculated within LSDA + U method. The ab-initio calculations are carried out using Atomistic ToolKit code, based on the density functional theory. The band structure and density of states calculations showed the half-metallic behavior for 12.5%, 6.25%, 3.125%, 1.5625% concentrations in ZnSe:Cr, ZnSe:V and ZnSe:Cr,V. The magnetic moments of Zn1-xCrxSe and Zn1-xVxSe supercells are 4 and 3 μB, respectively. Co-doping greatly raises the ferromagnetism and the value of total magnetic moment of the supercell is 7 μB. The defect formation energies were calculated and obtained that ferromagnetic state is more stable than antiferromagnetic state. The Curie temperatures are estimated for Zn1-xCrxSe and Zn1-xVxSe supercells for all studies concentrations. The results indicate that these materials are high Curie temperature DMSs. First-principles studies show that Cr- and V-doped ZnSe are promising materials for spintronics.

Effect of Co substitution on ferrimagnetic Heusler compound Mn3Ga

Effect of Co substitution on Mn3Ga is investigated using first-principles study for structural and magnetic properties. Without Co, ferrimagnetic Heusler compound Mn3Ga is in tetragonal phase. With Co substitution, depending on Co concentration (x), Mn3Ga prefers tetragonal (cubic) phase when x≤0.5 (x≥0.5). Ferrimagnetism is robust regardless of x in both phases. While magnetic moments of two Mn do not vary significantly with x, magnetic moments of Co in two phases exhibit different behaviors, leading to distinct features in absolute value of total magnetic moment (|Mtot|). When x≤0.5, in tetragonal phase, magnetic moment of Co is vanishingly small, resulting in a decrease of |Mtot| with x. In contrast, when x≥0.5, in cubic phase, magnetic moment of Co is roughly 1 μB, which is responsible for the increase of |Mtot|. Electronic structure is analyzed with partial density of states for various x. To elucidate the counterintuitively small Co moment, the magnetic exchange interaction is investigated, where exchange coefficient between Co and Mn(II) in x≤0.5 is much smaller than that in x≥0.5.

First-principles study of Co and Ni excess effects on crystal structure and phase stability of Co<sub>2</sub>NiGa alloy

Using the first-principles exact muffin-tin orbital method combined with the coherent potential approximation, the crystal structure and site occupation, martensitic transformation, magnetic moment and elastic constant for each of Co<sub>2+<i>x</i></sub>Ni<sub>1–<i>x</i></sub>Ga, Co<sub>2+<i>x</i></sub>NiGa<sub>1–<i>x</i></sub>, Co<sub>2–<i>x</i></sub>Ni<sub>1+<i>x</i></sub>Ga and Co<sub>2</sub>Ni<sub>1+<i>x</i></sub>Ga<sub>1–<i>x</i> </sub>(0 ≤ <i>x</i> ≤ 0.4) alloys with Co and Ni excess at 0 K are systematically investigated. It is shown that most of the austenitic phases of the alloys have <i>X</i>A stable structure, and the excess Co and Ni atoms occupy the insufficient atomic positions, and it is inversely occupied only when Ni replaces Ga. With the increase of <i>x</i>, the total electron energy of <i>L</i>1<sub>0</sub> relative to <i>X</i>A of only two Ga-insufficient alloys gradually decreases, for the former, the tetragonal shear elastic constant gradually increases, but for the latter, it gradually decreases. It is indicated that the martensitic transformation is promoted by the substitution of both Co and Ni for Ga in the energy and mechanics, and the martensitic transformation temperature is expected to increase. The values of total magnetic moment (<i>μ</i><sub>tot</sub>) of the <i>X</i>A phase and <i>L</i>1<sub>0</sub> phase of each alloy are mainly contributed by Co atoms, but onlya relatively small portion by Ni atoms. And the values of <i>μ</i><sub>tot</sub> of two phases in the four alloys have the same relationship with <i>x</i>, and the difference between them with the same compositions is not more than about 0.32 <i>μ</i><sub>B</sub> . The analyses of electronic structure calculations show that the distributions of spin-down electronic density of states of Co and Ni atoms near the Fermi energy level have contributed significantly to the stability of <i>L</i>1<sub>0</sub> relative to the <i>X</i>A phase, which is attributed to the Jahn-Teller effect. The above results are expected to provide a theoretical reference for the optimal design of the structure and properties of Co<sub>2</sub>NiGa-based ternary alloys.

First principle study of structural, electronic, magnetic, optical and thermal properties of chalcogenides XFeSe2 (X = Li, Na and K) half metallic compounds

Half-metallic ferromagnets (HMF) are one of the most essential materials for spintronics and other energy applications. The electronic, magnetic, optical and transport properties of hexagonal XFeSe2 (X = Li, Na and K) compounds have been investigated by Wien2K code. The Heisenberg classical model is used to determine spin polarization. The ferromagnetism is calculated by the negative exchange energy Δ x (pd), exchange constants, and quantum exchange of electrons in strong p-d hybridization. The integer values of total magnetic moment (M T) 5.0000 μ B, 4.9995 μ B, and 5.0000 μ B per unit formula for LiFeSe2, NaFeSe2 and KFeSe2, respectively, have confirmed the HMF. Optical properties are revealed in terms of absorption of light energy in visible to ultraviolet regions, refractive index, reflectivity spectrum and optical conductivity. Lastly, BoltzTraP code was used to explore the influence of electrical and thermal conductivities of electrons spin, potential gradient effect and figure of merit (ZT). Results reveal that the studied compounds are potential candidates for spintronic devices and energy applications.

A comprehensive investigation of structural and magnetic phase stability, electronic, magnetic and thermoelectric properties of Co2FeZ (Z = Al, Ga, Si, Ge, S, Se and Te) Full Heusler alloys

A series of full Heusler (FH) alloys Co2FeZ (Z = Al, Ga, Si, Ge, S, Se and Te) have been investigated using density functional theory (DFT) with full potential-linearized augmented plane wave (FPLAPW) method within generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof (PBE) functional. Most stable structures are determined by considering four different atomic arrangements i.e. L21-I/II (conventional) and XA-I/II (inverse) configurations. Stable magnetic phases like anti-ferromagnetic (AFM), nonmagnetic (NM) and ferromagnetic (FM) are evaluated and results revealed that FM phase is the most stable of all alloys. Spin band structures are calculated by applying GGA and GGA + mBJ approach. The results showed the half metallic nature of Co2FeAl and Co2FeGe alloys. The obtained band diagrams are compared with density of states (DOS) and revealed that the both Fe and Co atoms contributes maximum in total magnetic moment (MM). The calculated values of total magnetic moment (MT) of all compounds range from 4 to 6 μB and are in well agreement with the findings of Slater-Pauling Rule (SPR). Both alloys i.e. Co2FeAl and Co2FeGe showed 100% level of spin polarization (SP) at Fermi level. Mean field approximation (MFA) is employed to determine Curie temperature (Tc) and the values thus obtained are higher than room temperature. Furthermore, the thermoelectric parameters i.e. Seebeck coefficient (S) along with thermal (κ) and electrical (σ) conductivities for both Co2FeAl and Co2FeGe alloys are calculated and discussed in detail. The obtained results envisaged that the investigated alloys are suitable candidates for thermoelectric and spintronic applications.

Understanding the Interaction Between Fullerene and Graphene Nanoribbons Using Density Functional Theory

Carbon based heterostructures are extremely important in the field of material science as the junction of two carbon nanomaterials strongly influence the properties of a material. In present work, the structural, electronic and magnetic properties of covalently attached C60 cage with armchair and zigzag GNRs have been investigated using density functional theory. AGNR-nanobuds don't form stable structures, owing to their positive values of the interaction energy. However, pure and N/B doped ZGNR-nanobud form stable structures with [2+2]hhT mode, hence presenting the possibility of their formation. Average diameter for N doped ZGNR-nanobuds decreases as the C-N bond length is lower than the C-C bond length whereas average diameter for doped ZGNR increases due to the large C-B bond length. The considered complexes are magnetic in nature having a finite value of total magnetic moment. Increase in total magnetic moment is due to the induced localized magnetic moments near dopant sites, whereas decrease in the total magnetic moments is due to the reduction in magnetic moments at C-sites near connecting bond atoms. The significant variation in electronic density of states near the Fermi level leads to change in the metallic behaviour of ZGNR-nanobuds. Mulliken charge analysis shows that in N-doped nanobud, there is a transfer of charge from N to surrounding C atoms due to their electronegativity difference, and there is a gain in charge of B from surrounding C atoms. The unique electronic and magnetic properties of nanobuds can lead to the possible applications in the field of magnetic nano devices.

First-principle study of the new mechanism of alkaline earth metals and point defects on the magnetic properties of ZnO

Negative monovalent oxygen ions exist in oxides apart from negative divalent oxygen ions. This condition shows that the double exchange interaction model based on the basic assumption that all oxygen ions are negative divalent ions needs to be corrected. This study used first principles to investigate the magnetic mechanism of point defects on the ZnO: Be/Mg/Ca system. Results show that the binding energy of the three systems of Zn34MHiO36 (VZn1−, M = Be/Mg/Ca) is relatively the smallest, and the doped system has the best stability. The magnetism comes from the itinerant electrons produced by negative monovalent oxygen ions, and the absolute value of total magnetic moment is 1μB. The doping system d0 ferromagnetism theoretically provides a new mechanism for the magnetic origin of nonmagnetic materials and offers a new idea for the preparation of magnetic semiconductor materials.

Influence of vacancy defects on the electronic structure and magnetic properties of Cu-doped ZnO monolayers: A first-principles study

The development of available electronic structures and magnetism has received considerable interest for applications in nanoelectronic and spintronic devices. In this paper, we investigated the electronic and magnetic properties of Cu-doped defective ZnO monolayers by first-principles calculations. The results demonstrate that the formation energies of the VO + nCuZn complex under Zn-rich conditions are lower than those under O-rich conditions. However, the formation energies of the VZn + nCuZn complex under O-rich conditions are lower than those under Zn-rich conditions. Furthermore, the Cu dopant and vacancies both play an important role in the contribution of the magnetic moment. The total magnetic moments of the Cu2Zn14O15 monolayers remain at 1.822–1.868 µB, and the average local magnetic moment is approximately 0.439–0.443 µB per Cu atom. The magnetic moments of the O atoms close to the Cu atom are 0.124–0.163 µB per O atom. The magnetic moments of the VO + nCuZn complexes satisfy the odd-even doping rule, and the VO + nCuZn complexes undergo a transition from NM to FM with increasing Cu concentration. For the VZn + nCuZn complex, the total magnetic moments increase monotonically with an increase in the number of Cu atoms. The absolute value of total magnetic moment of the CuZn14O16 monolayer is 0.225 µB, which is contributed by the Cu dopant (0.433 µB), as well as the nearest O atoms around the Cu dopant. Furthermore, the combined effect of defect vacancy and Cu dopant could tune the ZnO monolayer from a direct semiconductor to an indirect semiconductor and even regulate the band gap. These findings are potentially useful for nanoelectronic and spintronic applications.

Structural, electronic, magnetic and mechanical properties of the full-Heusler compounds Ni2Mn(Ge,Sn) and Mn2NiGe

Abstract Mn-Ni based full-Heusler alloys belong to novel half-metallic compounds with a promising set of physical properties for applications as functional materials. Based on first principles calculations, the electronic structures, the magnetic and mechanical properties of Ni2Mn(Ge,Sn) and Mn2NiGe full-Heusler alloys have been investigated in detail. The results revealed that the Mn2NiGe with Hg2CuTi type structure is more stable; on the other hand, for Ni2Mn(Ge,Sn), the Cu2MnAl type structure is more stable. The Mn2NiGe alloys are found to be half-metallic with an integer value of total magnetic moment of 4 μB which makes them interesting materials in the field of spintronics. The Ni2Mn(Ge,Sn) alloys exhibit metallic character in both Hg2CuTi and Cu2MnAl type structures. The calculated B/G ratios for all the considered compounds Ni2Mn(Ge,Sn) and Mn2NiGe are greater than 1.75; therefore, these alloys are ductile, and the calculated Cauchy’s pressure is positive, which also classified these compounds as ductile materials.

Electronic, magnetic, optical and transport properties of wurtzite-GaN doped with rare earth (RE= Pm, Sm, and Eu): First principles approach

A density functional theory (DFT) and semiclassical Boltzmann transport equations (BTE) has been used to explore the electronic, magnetic, optical and transport properties of Ga1−xRExN (RE=Pm, Sm, and Eu). We have studied the impact of doping of rare-earth (RE) elements on GaN wurtzite structure. In all the doped systems, the stability is ferromagnetic state with minimum ground state energy. Our theoretical calculations revealed that all the doped compounds exhibit half-metallic ferromagnet (HMF) behavior with 100% spin polarization at the Fermi level witin GGA, mBJ and Spin-orbit coupling (SOC). However, within GGA+U, Ga1−xRExN exhibits dilute magnetic semiconducting behaviour with exact integer value of total magnetic moment. A large gap was established with the concentrations of 6.25%, 12.5%. The shift of fermi energy towards the bottom of the conduction band, make these systems an n-type. The mechanism of ferromagnetism in this system has been proposed according to this positioning. The majority-spin density of states (DOS) mainly comprises of Eu-4f states appears in the energy gap. Yet, in the case of the Pm, and Sm-doped GaN, some part of the impurity states of 4f lies below Fermi energy (Ef). The optical absorption for RE-doped GaN is significantly enhanced, in the ultraviolet region. We have noticed the improvement of electrical conductivity as compared to the pristine one for both the concentrations. These features, make RE-doped GaN a transparent material for optoelectronic tools.

Prediction of the Half Metallicity in Ferromagnetic Germanium Telluride (GeTe) Doped with Titanium

This research work studies the structural, electronic and magnetic properties of Ge[Formula: see text]TixTe (for [Formula: see text], 0.50, 0.75, 1) compounds in rock-salt structure based on first-principles spin-polarized density functional theory. As it is implemented in WIEN2k code, the full-potential augmented plane-wave method was used in the investigation. To evaluate the structural properties of compounds, the exchange-correlation term is estimated using PBE-GGA approximation. For the other properties such as the electronic structures, densities of states and local moments, the generalized gradient approximation PBE-[Formula: see text] is used. The analysis of spin-polarized density of states has shown the half-metallic ferromagnetic character when [Formula: see text] and 0.75; while at [Formula: see text], we obtained near half-metallic behavior. In order to validate the effects resulting from exchange splitting process, we calculated the exchange constants [Formula: see text] and [Formula: see text]. For Ti atomics sites, the value of total magnetic moment has been estimated equal to [Formula: see text] in all studied compounds. We have found that the local magnetic moment of Ti is reduced and small local magnetic moments on nonmagnetic atomics sites of Ge and Te were created by the p-d hybridization effect.

Influence of Pr substitution on the physical properties of the Ce1−xPrxCoGe3 system: Combined experimental and first-principles study

We present the results of our investigations of physical properties for the novel Ce$_{1-x}$Pr$_x$CoGe$_3$ system performed with a number of experimental methods: magnetic susceptibility, specific heat, electrical resistivity, magnetoresistance, and thermoelectric power. Moreover, the electronic structure was studied by means of photoelectron spectroscopy measurements and first-principles calculations. All investigated compositions of the Ce$_{1-x}$Pr$_x$CoGe$_3$ series crystallize in the tetragonal BaNiSn$_3$-type structure. The lattice parameters and unit cell volumes decrease with increasing Pr concentration. On the basis of the measurements taken, a preliminary magnetic phase diagram was created. A continuous suppression of the long-range magnetic ordering was observed with increase of Pr concentration. The critical Pr concentration for magnetic moment ordering was determined from linear extrapolation of the ordering temperature $versus$ $x$ to the lowest temperatures ($T = 0$ K) and is equal to about 0.66. Based on the first-principles calculations we show how the substitution of Pr for Ce affects the electronic structure and magnetic properties of the considered alloys. Within a single model we take into account the magnetic ordering, fully-relativistic effects, and Hubbard U repulsion on Ce and Pr. The impact of Hubbard U on the results of calculations is also discussed. We present the valence-band analysis, Mulliken electronic population analysis, and calculated electronic specific heat coefficients. For CeCoGe$_3$ it is found that the $++--$ configuration of magnetic moments on Ce is slightly more stable than the $+-+-$ one, and also that the calculated value of total magnetic moment on Ce (including spin and orbital parts) is in good agreement with the measurements.

Electronic and Thermoelectric Properties of Li-Based Half-Heusler Alloys: A DFT Study

Abstract In this paper, we have studied the electronic, elastic and thermoelectric properties of the half-Heusler LiCrZ (Z = C, N, Si, and P) materials in Type II phase, in this structure the atomic occupations are X (1/2,1/2,1/2), Y (0,0,0) and Z(1/4,1/4,1/4). The ferromagnetic state of Type II structure was found to be the most stable phase for all studied alloys. After calculating the elastic constants, we found out that the conditions of mechanical stability were verified only for LiCrSi and LiCrP alloys in Type II phase, at both equilibrium a0 and half metallic ahm lattice constants, which indicates that these two compounds can be synthesized experimentally. We should also mention that the half metallic behavior in Type II structure, for LiCrSi and LiCrP compounds, was obtained by straining the equilibrium lattice constants by 2% and 6%, respectively. At ahm, these two systems were identified to be true half metals due to their complete spin polarization and integer value of total magnetic moment. These last ones have reached 3μB per unit cell when Z = Si, and 4μB when Z = P. Using the mean field approximation (MFA), the Curie temperatures of Type II structure were also determined, where the values are estimated to be 456.2 K and 302.8 K, respectively. Finally, the thermoelectric performance has been explored by the classical Boltzmann theory. At low temperatures, the figure of merit has reached 0.73 and 0.93 for LiCrSi and LiCrP, respectively. The considerable ZT values and all calculated physical properties make these two systems promising candidates for thermoelectric applications.

Semiconducting and magnetic properties within B(1-x)VxAs alloys at x = 0 and x = 0.25: A DFT + U study

The physical (mechanical (structural and elastic), electronic and magnetic) properties of the zincblende BAs parent compound and its B0.75V0.25As alloy are analyzed by employing the FP-L/APW + lo method as implemented in WIEN2k code, where the XC potential is approached by the GGA approximation. The analysis of the structural properties in B0.75V0.25As system indicates its stability in ferromagnetic state, where its computed equilibrium lattice parameters (the lattice constant (a0), the bulk modulus (B0), and the first-pressure derivative (B’) of the bulk modulus) are given. The elastic moduli (C11, C12, and C44) and anisotropy factor for the cubic system are determined for these compounds in the purpose to confirm their mechanical stability. The electronic structure of B0.75V0.25As shows its complete semiconducting feature. The electronic density of states indicates that the uncompleted 3d-V orbitals broaden on the width of the exchange splitting energies (Δx(d) and Δx(pd)); accordingly, the effective potential of minority-spin electrons are more attracted comparing to the majority-spin electrons. The magnetic properties unveil that the value of total magnetic moment of B0.75V0.25As alloy is found in an integer number. Thus, the hybridization between 3d-V and 4p-As states pushes to reduce the atomic magnetic moment of V element from its free space charge value and to produce local magnetic moments on B and As nonmagnetic sites. Moreover, the s-d exchange constant of conduction band (N0α) and the p-d exchange constant of valence band (N0β) are evaluated in the reason to know contributions during the exchange splitting process.

Structural, electronic, magnetic and optical properties of AB2O4 (A = Ge, Co and B = Ga, Co) spinel oxides

Structural, magnetic, optical and electronic properties of GeGa2O4, CoGa2O4, GeCo2O4 and CoCo2O4 spinel oxides have been studied. Spinel oxides are studied by performing theoretical calculations based on density functional theory. In non-magnetic host GeGa2O4 spinel oxide, significant effects of Co occupancy (at A, B and/or both sites) on the electronic, magnetic and optical behavior have been observed. Among the spinel oxides, the CoGa2O4, GeCo2O4 and CoCo2O4 spinel oxides show 100% spin-polarization and exhibit stable cubic structure in ferromagnetic phase. The calculated structural and magnetic parameters predict the cation distribution at A and B sites as follows: (Ge2+)[Ga23+]O4−2, (Co2+)[Ga23+]O4−2, (Ge4+)[Co22+]O4−2 and (Co+2)[Co23+]O4−2 for GeGa2O4, CoGa2O4, GeCo2O4 and CoCo2O4 spinel oxides, respectively. The electronic band gap is found to be decreased from 1.605 eV to 0.762 eV for spin↑ state while it is decreased from 1.578 eV to 0.000 eV for spin↓ state with Co occupancy in host GeGa2O4 lattice. Lattice constant decreases (8.7877 Å to 8.1390 Å) as Co occupies B site and/or both (A and B) sites. For GeCo2O4 spinel oxide, the calculated value of total magnetic moment (mtot = 6.12 μB/f.u) and saturation magnetization (MS = 134.22 emu/g) is found to maximum. Optical properties reveal that the CoGa2O4, GeCo2O4 and CoCo2O4 spinel oxides have less threshold electronic transition energy relative to host GeGa2O4 spinel oxide. Electronic, magnetic and optical characteristics show potential integration of these spinel oxides in magnetic-semiconducting devices.