Narrow Results

We have investigated the magnetic and magnetotransport properties of monophasic double perovskites Sr₂FeMO₆(M = Mo, W). Magnetic measurements indicate that SFMO is a ferromagnet and SFWO is an antiferromagnet with T_N = 35 K at H = 5 T. Large magnetoresistance ratio (MR) of ~ 22% (H = 3 T) at room temperature (RT) was observed in the SFWO compound. However, the SFMO compound did not show any significant MR even at high fields and RT (MR~1%; H = 3 T and 300 K). The changes observed by physical measurements are supported by band structure calculations to explain the interaction between the 3d(Fe), 4d(Mo) and 5d(W) orbitals of transition metal ions and oxygen ions.

The results of first principles calculations of the electronic band structures, density of states, band gap, equilibrium lattice constants, cohesive energies, bulk moduli and magnetic moments are presented for the EuN with rock salt as ambient structure and cesium chloride as high-pressure structure. The tight-binding linear muffin tin orbital method within the local-density approximation is used. Both spin-polarized and non-spin polarized calculations are performed. The magnetic and structural stabilities are determined from the total energy calculations for both nonmagnetic (NM) and ferro-magnetic (FM) states. From the present study EuN illustrates half-metallic. The FM phase is more stable than NM phase. We further predict EuN undergoes a transition from NaCl-type (B₁) to CsCl-type structure (B₂) at 14.6 GPa, which could not be compared owing to the need of experimental and theoretical results. Futhermore, the bulk moduli, first-order pressure derivatives and magnetic moments are also estimated in B₁ and B₂ phases. The magnetic moment is estimated to be nearly 6 μ_B, which is in good agreement with the others reported value. A small decrease in magnetic moment is observed under pressure.

In this paper, spin-polarized density functional calculations on the structural, electronic, optical and magnetic properties of the zincblende structure of the ${\mathrm{\text{Zn}}}_{1-x}{\mathrm{\text{V}}}_x\mathrm{\text{S}}$ and ${\mathrm{\text{Cd}}}_{1-x}{\mathrm{\text{V}}}_x\mathrm{\text{S}}$ alloys at $x=0.25$ in the ferromagnetic (FM) ordering has been investigated. The study is accomplished using the full-potential (FP) linearized augmented plane wave plus local orbital (LAPW$+$lo) self-consistent scheme of calculations. To incorporate the exchange correlation component in the total energy calculations of the crystal, Perdew–Burke and Ernzerhof (PBE) parameterization for the generalized gradient approximation (GGA) and GGA$+$U are employed. Basically, for both alloys, to address their structural properties, we calculated their equilibrium lattice constants, bulk moduli as well as pressure derivatives. In general, from the analysis of the obtained electronic band structure of these alloys, the half-metallic nature of ${\mathrm{\text{Zn}}}_{0.75}{\mathrm{\text{V}}}_{0.25}\mathrm{\text{S}}$ and nearly half-metallic nature of the ${\mathrm{\text{Cd}}}_{0.75}{\mathrm{\text{V}}}_{0.25}\mathrm{\text{S}}$ alloy are demonstrated. The plotted density of states (DOS) curves project spin-exchange splitting energy ${\mathrm{\Delta }}_x(d)$ and ${\mathrm{\Delta }}_x(pd)$ as generated by V-3d states. It has been clearly evident that the effective potential results for the spin-down case are more striking than for the spin-up case. In order to describe the magnetic behavior of these alloys, the exchange constants $N_{0\alpha }$ (valence band) and $N_{0\beta }$ (conduction band) as well as the magnetic moment values are estimated. The calculated results of the magnetic moment show that the main source in the reduction of the local magnetic moment of V in the alloys in comparison with its free value is a $p$–$d$ orbital hybridization and partial transfer to nonmagnetic sites of (Zn, S) and (Cd, S) in ${\mathrm{\text{Zn}}}_{0.75}{\mathrm{\text{V}}}_{0.25}\mathrm{\text{S}}$ and ${\mathrm{\text{Cd}}}_{0.75}{\mathrm{\text{V}}}_{0.25}\mathrm{\text{S}}$ alloys. In addition, a study concerning optical properties, such as the refractive index, reflectivity and absorption coefficients is performed to determine their potential for optical and optoelectronic devices.

In this work, detailed electronic structure calculations of alkali metal fluorides A₂MnF₆ (A = K, Rb, Cs) have been performed using ab-initio calculating techniques based on density functional theory (DFT). We applied different exchange correlation functionals, namely Wu–Cohen generalized gradient approximation (WC-GGA), modified Becke Johnson potential (mBJ) and GGA plus Hubbard U method in order to treat the exchange correlation energy. The calculated lattice constants are found in excellent agreement with earlier experimental results. The electronic band structure and density of states show that Cs₂MnF₆ is half metallic, exhibiting semiconductivity in spin up direction and metallic behavior in spin down direction. The compounds, K₂MnF₆ and Rb₂MnF₆, are predicted as wide bandgap materials. The DFT + U method gives quite accurate results of the electronic bandgap as compared with other approximations. The states Mn-3d and F-2p contribute largely to the conduction and valence energy bands. Additionally, magnetic calculations reveal strong ferromagnetic nature of these compounds. The half-metallic nature along with ferromagnetism make Cs₂MnF₆ a promising candidate for future applications in spintronics. Furthermore, the wide bandgap observed in K₂MnF₆ and Rb₂MnF₆ indicate their utility for light-emitting diodes (LEDs) transparent lenses and optical coatings.

In this work, the first-principles density functional calculations of the structural, elastic, electronic, magnetic, thermal and thermoelectric properties of NiVSn half-Heusler compound are carried out. The exchange and correlation potential are treated by using Generalized Gradient approximation of Perdew, Burke and Ernzerhof (GGA-PBE), GGA plus Tran–Blaha-modified Becke–Johnson (mBJ-GGA) approach and mBJ-GGA+U where U is the Hubbard on-site Coulomb interaction correction (mBJ-GGA+U). Structural calculations revealed that NiVSn is stable in type 1 structure ferromagnetic state. Elastic properties show that our compound is mechanically stable, ductile and anisotropic. The results of the band structures and density of states display a half metallic behavior of NiVSn with an indirect bandgap of 0.476, 0.508 and 0.845 eV by using GGA-PBE, mBJ-GGA, and mBJ-GGA+U, respectively. The total magnetic moment calculated is integer of 1 $\mu$B confirming a half metallic behavior of NiVSn and follows the well-known Slater–Pauling rule (${\mu }_{\mathrm{\text{tot}}}=Z_{\mathrm{\text{tot}}}-18$); therefore, the studied compound is suitable for application in spintronic fields. The thermodynamic properties such as bulk modulus, the heat capacity, the Debye temperature, and the thermal expansion coefficient are investigated using quasi-harmonic Debye model (QHDM). The thermal results show that NiVSn can be applied in extreme temperature and pressure conditions. The thermoelectric properties are studied employing the BoltzTrap code. The calculated transport properties are very interesting for the spin-down channel with high electrical conductivity, high Seebeck coefficient, and figure of merit value approaching unity. As a result, the half-Heusler alloy NiVSn is a promoter for conventional thermoelectric materials.

This work reports first-principle calculations for LiMgP half-Heusler compound doped by the transition metal elements Cr, Mn, Co and Ni motivated by present findings, in which the ferromagnetism conduct is predicted. The studied LiMg${}_{0.95}{Y}_{0.05}$P alloy ($Y=\mathrm{\text{Cr}}$, Mn, Co and Ni) showed the ferromagnetic behavior. The calculations revealed that the main contributions to the net magnetization come from Cr, Mn, Co and Ni. The Cr${{}^2}^{+}$ will have four electrons, in which 2 electrons are in $e^{+}$ and other 2 occupy the $t_2^{+}$. Then, this orbital is set on the Fermi level. For LiMg${}_{0.95}$Co${}_{0.05}$P alloy, the half-metallic conduct is estimated with 100% polarized on the downside of the Fermi level. Also, LiMg${}_{0.95}$Ni${}_{0.05}$P alloy exhibits the half-metallic conduct on the downside of the Fermi level which is occupied by $t_2^{-}$ minority state. This study stated that electronegativity and magnetic properties have correlation with regard to Cr-, Mn-, Co- and Ni-doped LiMgP, in which the trends of partial moments, electronegativity and total moments are $M^{\mathrm{\text{Ni}}}<M^{\mathrm{\text{Co}}}<M^{\mathrm{\text{Cr}}}<M^{\mathrm{\text{Mn}}}$; ${\chi }^{\mathrm{\text{Ni}}}>{\chi }^{\mathrm{\text{Co}}}>{\chi }^{\mathrm{\text{Cr}}}>{\chi }^{\mathrm{\text{Mn}}}$ and $M_{{\mathrm{\text{LiMg}}}_{0.95}{\mathrm{\text{Ni}}}_{0.05}\mathrm{\text{P}}}^{\mathrm{\text{Tot}}}<M_{{\mathrm{\text{LiMg}}}_{0.95}{\mathrm{\text{Co}}}_{0.05}\mathrm{\text{P}}}^{\mathrm{\text{Tot}}}<M_{{\mathrm{\text{LiMg}}}_{0.95}{\mathrm{\text{Cr}}}_{0.05}\mathrm{\text{P}}}^{\mathrm{\text{Tot}}}<M_{{\mathrm{\text{LiMg}}}_{0.95}{\mathrm{\text{Mn}}}_{0.05}\mathrm{\text{P}}}^{\mathrm{\text{Tot}}}$.

This paper aims to investigate the behavior of LiMgN half-Heusler (HH) semiconductor doped by transition metals (TM $=$ Mn, Fe, Co and Ni). HHs belong to the $F\bar{4}3m$ space group (No. 216) and have a zinc blende structure that can be described by the chemical symbol XYZ. The research methodology utilized in this investigation involves theoretical analysis based on the principles of density functional theory (DFT). The studied LiMg${}_{0.95}$TM${}_{0.05}$N alloy displayed the half-metallicity behavior when TM $=$ Fe, Co and Ni. Hence, these systems could be a promising candidate in spintronic application thanks to their ferromagnetism. The principal contribution to magnetism in the full LiMg${}_{0.95}$TM${}_{0.05}$N alloys comes from the Mn, Fe, Co and Ni doping. The partial magnetic moments of these elements are significantly greater than the combined partial magnetic moments of Li, Mg and N. When comparing LiMg${}_{0.95}$Mn${}_{0.05}$N to LiMg${}_{0.95}$Fe${}_{0.05}$N, ₅Co${}_{0.05}$N and LiMg${}_{0.95}$Ni${}_{0.05}$N, it is important to note that the exchange splitting energy ${\mathrm{\Delta }}_{(e^{+},e^{-})}^{\mathrm{\text{TM}}}$ associated to their spin up and spin down were discussed. The variation of Mn(3d) in relation to ($e^{+},e^{-}$) is larger than that of Fe, Co and Ni. Therefore, ${\mathrm{\Delta }}_{(e^{+},e^{-})}^{\mathrm{\text{Mn}}}>{\mathrm{\Delta }}_{(e^{+},e^{-})}^{\mathrm{\text{Fe}}}>{\mathrm{\Delta }}_{(e^{+},e^{-})}^{\mathrm{\text{Co}}}>{\mathrm{\Delta }}_{(e^{+},e^{-})}^{\mathrm{\text{Ni}}}$. Furthermore, there is a correlation between the magnetic moment and electronegativity trend of the TM dopant. Specially, the electronegativity trend (${\chi }^{\mathrm{\text{TM}}})$ is well matched with the total spin moment trend, where ${\chi }^{\mathrm{\text{Ni}}}>{\chi }^{\mathrm{\text{Co}}}>{\chi }^{\mathrm{\text{Fe}}}>{\chi }^{\mathrm{\text{Mn}}}$.

This is an ab initio study instituted on the density functional theory (DFT) and the full-potential linearized augmented plane wave (FP-LAPW) calculations that are performed to analyze the mechanical, electronic, optical and thermoelectric properties of the cubic MCoF₃ compound (M = K and Rb). The studied compounds are found thermodynamically and mechanically stable. Moreover, these compounds are found to be elastically anisotropic and ductile. KCoF₃ and RbCoF₃ are classified as half-metallic and anti-ferromagnetic compounds. The optical properties are investigated from the dielectric function for the different energy ranges. The thermoelectric properties such as transport properties are determined as a function of temperature using BoltzTrape code in the range of 20–800 K. The present compounds are found to have p-type character. Also, the majority charge carriers are found to be electrons rather than hole. Useful mechanical, spintronic, optical and thermoelectric applications are predicted based upon the calculations.

This study analyzes how adding europium and transition metals (Cu, Ag, and Au) at a 12.5% concentration to magnesium oxide (MgO) affects its physical characteristics and potential uses. To do so, the full potential linearized augmented plane wave (FP-LAPW) method, based on spin-polarized density functional theory (SP-DFT), is used to derive the results. Wu and Cohen’s generalized gradient approximation (GGA-WC) described the exchange-correlation potential. The modified Becke-Johnson exchange potential (TB-mBJ) was also used to improve the findings of optoelectronic properties. When Eu and TM (Cu, Ag, and Au) impurities are co-doped into the nonmagnetic (NM) semiconductor MgO, the structural optimization results show that the lattice constants increase, and the bulk modulus decreases with increasing the atomic number of transition metals. The resulting dilute magnetic oxides (DMOs) are stable in the spin-polarized ferromagnetic (FM) phase, and the formation energy values confirm their stability in the $Fm\bar{3}m$ cubic structure, with the lowest value belonging to Eu${}_{0.125}$TM${}_{0.125}$Mg${}_{0.750}$O. Similarly, calculations of electronic properties using the WC-mBJ functional demonstrate that all compounds have an indirect half-metallic bandgap at L-$\mathrm{\Gamma }$ equal to 2.53, 2.49, and 1.39 eV for Eu${}_{0.125}$Cu${}_{0.125}$Mg${}_{0.750}$O, Eu${}_{0.125}$Ag${}_{0.125}$Mg${}_{0.750}$O, and Eu${}_{0.125}$Au${}_{0.125}$Mg${}_{0.750}$O, respectively. They have an integer magnetic moment of 6 ${\mu }_B$. The density of states shows that at the Fermi level, the 4f-Eu, d-TM, and p-O states give rise to new energy levels. This indicates that the f–p–d hybridization provides this system with its FM properties. Also, these compounds’ dielectric function and absorption spectra are calculated and analyzed to learn more about their optical properties. The results provide insight into the optical behavior of the materials. It is observed that the co-doped compounds exhibit greater optical absorbance than their un-doped MgO counterparts do. This theoretical investigation opens the way to preparing high magnetic moment DMOs using TM and rare earth as dopants suitable for spintronic and UV devices.

The structural, electronic and magnetic properties of FeCr₂O₄ and CrFe₂O₄ spinels have been investigated by the first-principles approach based on density functional theory (DFT) and the full-potential linearized augmented plane-wave method, within the generalized gradient approximation (GGA-PBE) and GGA-$\mathrm{\text{PBE}}+U$ scheme. The stability of these spinels in the normal and inverse phases is evaluated.

The spin-polarized electronic band structures and density of states of FeCr₂O₄ calculated by GGA-PBE and GGA-$\mathrm{\text{PBE}}+U$ show that the minority spin channel has metallic nature and the majority spin channel has a half-metallic (HM) gap of 0.25eV and 1.30 eV, respectively. CrFe₂O₄ shows that both minority and majority spin channels have metallic nature when using GGA-PBE and half-semiconducting behavior with half-semiconductor gap of 0.71eV when using GGA-$\mathrm{\text{PBE}}+U$, with magnetic moment of 2${\mu }_B$ per formula unit. Analysis of density of states of these compounds indicates that the magnetic moment mainly originates from the strong spin-polarization of 3$d$ states of Fe and Cr atoms. Presence of HMF in FeCr₂O₄ and CrFe₂O₄ spinels makes these compounds promising compounds for spintronic applications.

The full-potential linearized augmented plane waves (FP-LAPW) method, within the density functional theory (DFT), has been used to investigate the structural and elastic properties of KRbAs, KNaAs and NaRbAs. The obtained results, utilizing the generalized gradient approximation (GGA), revealed that all compounds prefer their type-I structure ferromagnetic (FM) phase. However, only two among them, KRbAs and KNaAs, exhibit a mechanical stability thus the electronic and magnetic properties have been calculated for both compounds. In the electronic properties, we found that both compounds show a half-metallic character with direct gaps of 1.114eV and 1.514eV, in the spin-up channel, for KNaAs and KRbAs, respectively. Thus, they may be potential candidates for spin injection in the field of spintronic applications. Moreover, their integer calculated total magnetic moment of $1{\mu }_B$ agrees with the Slater–Pauling rule.

The structural electronic and magnetic properties of the double perovskite Ca₂CrNbO₆ in the cubic structure are investigated using the empirical full-potential linearized augmented plane wave (FP-LAPW) method within the framework of the spin-polarized density functional theory (DFT). These properties are calculated using the Generalized Gradient Approximation (GGA), $\mathrm{\text{GGA}}+U$ and modified Becke–Johnson mBJ-GGA. In addition, the real and imaginary parts of the optical dielectric function and the reflectivity, and the refractive spectra are computed and the main features shown by their spectra are ascertained on the base of the investigation of density of states.

The structural, electronic, elastic and magnetic properties of CoCrScIn were investigated using first principle calculations with applying the full-potential linearized augmented plane waves (FP-LAPW) method, based totally on the density functional theory (DFT). After evaluating the results, the calculated structural parameters reveal that CoCrScIn compound is stable in its ferrimagnetic configuration of the type-III structure. The mechanical properties show its brittle and stiffer behavior. The formation energy value showed that CoCrScIn can be experimentally synthesized. Additionally, the obtained band structures and density of states (DOS) reflect the half-metallic behavior of CoCrScIn, with an indirect bandgap of 0.43eV. The total magnetic moment of 3${\mu }_B$ and half-metallic ferrimagnetic state are maintained in the range 5.73–6,79 Å. The magnetic moment especially issues from the Cr-$d$ and Co-$d$ spin-polarizations. Furthermore, the calculations of Curie temperature reveal that CoCrScIn has high magnetic transition temperature of 836.7K.

In this paper, the structural, electronic, magnetic, and half-metallic properties of full-Heusler alloys Mn₂ZrX ($\mathrm{\text{X}}=\mathrm{\text{As}}$, Bi) in the Hg₂CuTi-type structure have been studied by using the first-principles-based density functional theory (DFT) with the full-potential linearized augmented plane-wave (FP-LAPW) method. Mn₂ZrX ($\mathrm{\text{X}}=\mathrm{\text{As}}$, Bi) compounds are found to be half-metallic ferrimagnets. The calculated total magnetic moments of the Mn₂ZrX ($\mathrm{\text{X}}=\mathrm{\text{As}}$, Bi) alloys are estimated at 01${\mu }_B$ according to the Slater–Pauling rule of $M_{\mathrm{\text{tot}}}=$ ($Z_{\mathrm{\text{tot}}}$–24) ${\mu }_B$. It was discovered that Mn₂ZrAs and Mn₂ZrBi maintained their half-metallicity for a lattice constant interval of 5.72 to 6.26 Å and 6.33 to 6.62 Å, respectively, and present a maximum degree of spin polarization at the Fermi level. In addition, the predicted formation energy and elastic parameters show that these materials are mechanically stable. All of these results indicate that these new Mn₂-based heusler alloys are able to be the candidates for spintronic applications.