Electronic Structure and Magnetism of Pristine, Defected, and Strained Ti2N MXene

From first principles electronic structure calculations, we unravel the evolution of structural, electronic, and magnetic properties of pristine, defected, and strained titanium nitride MXene with different functional groups (-F, -O, -H, and -OH). The formation and cohesive energies reveal their chemical stability. The MAX phase and defect free functionalized MXenes are metallic except for oxygen terminated (Ti 2 NO 2 ) one which is 100% spin polarized half-metallic ferromagnet. The spin-orbit coupling significantly influences the bare MXene (Ti 2 N) to exhibit Dirac topology and band inversion near the high symmetry directions and Fermi level. The strain effect sways the Fermi level thereby shifting it toward lower energy state under compression and toward higher energy state under tensile strain in Ti 2 NH 2 . The Ti 2 NO 2 exhibits exotic electronic structure and magnetic states not only in pristine but also in strained and defected structures. Its half-metallic nature changes to semi-metallic under 1% compression and it is completely destroyed under 2% compression. In single vacancy defect, its band structure remarkably transforms from half-metallic to semi-conducting with large band gap in 12.5% Ti, weakly semi-conducting in 5.5% Ti, and semi-metallic in 12.5% O. The 25% N defect changes it’s half-metallic characteristic to metallic. Further, the 12.5% Co substitution preserves it’s half-metallic character, whereas Mn substitution allows it to convert half-metallic characteristic into weak semi-metallic characteristic preserving ferromagnetism. However, Cr substitution converts half-metallic ferromagnetic state to half-metallic anti-ferromagnetic state. The understanding made here on collective structural stability, and electronic band structure, and magnetic phenomena in novel 2D Ti 2 N derived MXenes open up their possibility in designing them for synthesis and thereby taking to applications.

The Lithium (Li) Doping Effect for Enhancing Thermoelectric and Optoelectronic Performances of Co2NbAl

Cobalt -rich Heusler compounds represent a very interesting family among Heusler alloys due to their performance in the field of spintronics and magnetic devices. The quaternary Heusler created by swapping of an anti-atom site by an alkali element improves the performance of physical properties for new applications. In this study, the electronic structures and magnetic properties before and after swapping cobalt (Co) by lithium (Li) in the Co2NbAl compound have been investigated using first-principle computational calculations. Our findings revealed that the swapping Co antisite by Li keeps the half-metallic character in the CoLiNbAl. Analysis of band structures show that ternary Heusler compound is ferromagnetic half-metallic with half metallic gap (band gap in minority channel ) equal 0.134 eV but the swapping Co with Li leads the material to change its behavior and becomes a semiconductor with a gap equal 1.043 eV using HSE06 approach. The results of optical and thermoelectric properties such as absorption coefficient, reflectivity or thermopower and figure of merit are very interesting in the optoelectronic field and encourages the researchers to realize photovoltaic cell and thermoelectric generator with a higher efficiency. These interesting features suggest that Co2NbAl and LiNbAlCo Heusler compounds could be good candidates for applications of antiferromagnetic spintronics and optoelectronics in commercial semiconductor industry.

Half-metallic Ferromagnetism in Non-magnetic Double Perovskite Oxides Sr2MSbO6 (M=Al, Ga) Doped with C and N.

Double perovskite oxides have gained tremendous attention in material science and device technology due to their facile synthesis and exceptional physical properties. In this paper, we elucidate the origin of magnetization in non magnetic double perovskite oxides Sr2MSbO6 (M=Al, Ga) induced by non-magnetic 2p-impurities (C and N) substituted. The calculations were done within the full potential linearized augmented plane wave method (FP-LAPW) in the framework of the density functional theory (DFT). The exchange-correlation potential is evaluated using the generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) and the modified Becke and Johnson (mBJ-GGA). Regarding structural properties of undoped double perovskites Sr2MSbO6 (M=Al, Ga), we found that the lattice constants and oxygen positions are in rational accord with the experimental results. Furthermore, both of the examined compounds are brittle in nature with isotropic character. For Sr2AlSbO6 we have got the values of energy gap equal to 1.9 eV and 3.7 eV within the GGA and the mBJ-GGA, respectively. However for Sr2GaSbO6 the values of energy gap obtained in GGA and mBJ-GGA are equal to 0.8 eV and 2.9 eV, respectively. Finally, spin-polarized calculations reveal that the doping C and N can lead to drastic changes in the magneto-electronic properties of the semiconducting Sr2MSbO6 matrix with the integer magnetic moment of 6.00 µB and exhibit half-metallic properties. The origin of ferromagnetism can be attributed to the spin–split impurity bands inside the energy gap of the semiconducting Sr2MSbO6 matrix. These results may help experimentalists in synthesizing new double perovskites for spintronic applications.

First-principles investigations of the half-metallic ferromagnetic LaCoTiIn equiatomic quaternary Heusler alloy for spintronics

We have evaluated the structural and mechanical stability, electronic structure, total spin magnetic moment, and Curie temperature of LaCoTiIn Equiatomic Quaternary Heusler Alloy (EQHA) using first-principles studies. The Generalized Gradient Approximation (GGA) and GGA+U schemes have been used as exchange-correlation functional for the above calculations. From the ground state calculation, LaCoTiIn EQHA with a Type-III structure in the ferromagnetic (FM) state is found to be stable. The electronic structure of LaCoTiIn EQHA depicts half-metallic behavior which has metallic overlap in the spin up ([Formula: see text] channel and a semiconductor band gap in the other channel. The spin–orbit coupling of LaCoTiIn has a great influence on the band gap of the material. The computed band gap values for the spin down ([Formula: see text] channel are 0.480 eV and 0.606 eV by using the GGA and GGA+U schemes. The total spin magnetic moment is 1 [Formula: see text], according to the Slater–Pauling rule, [Formula: see text] = ([Formula: see text] - 18) [Formula: see text]. These results obtained can be used as a valuable reference for future research, or they will be used to further motivate the experimental synthesis of the corresponding alloy.

Robust Half-Metallic Character In KMnGe Half-Heusler Compound

The search for spin injectors and spin sources in spintronic devices is a significant facet of materials research today. Consequently, half-Heusler (HAH) KMnGe alloy has been recommended as one such admissible materials. Herein, a rigorous examination of the structural, magnetic and electronic properties of HAH KMnGe alloy is done using ab initio method within the bolstered up rendition of the functional by Perdew and his group. Our result shows that HAH KmnGe alloy expresses type-1 and type-2 HAH structural ground state at high and low pressures respectively, which may pose a challenge in application. Impressively, HAH KMnGe alloy exhibits half metallic characteristic with an indirect energy gap in the Γ-X symmetry k-point and direct band gap at X-point in the minority electronic spin states for type-1 and type-2 phase respectively. Our findings agree fundamentally with some previous findings in the literature and suggests that the HAH KMnGe alloy is a credible excellent spin source in future spintronic devices.