Recent Advances in Novel Materials for Future Spintronics

As we all know, electrons carry both charge and spin. The processing of information in conventional electronic devices is based only on the charge of electrons. Spin electronics, or spintronics, uses the spin of electrons, as well as their charge, to process information. Metals, semiconductors, and insulators are the basic materials that constitute the components of electronic devices, and these types of materials have been transforming all aspects of society for over a century. In contrast, magnetic metals, half-metals (including zero-gap half-metals), magnetic semiconductors (including spin-gapless semiconductors), dilute magnetic semiconductors, and magnetic insulators are the materials that will form the basis for spintronic devices. This book aims to collect a range of papers on novel materials that have intriguing physical properties and numerous potential practical applications in spintronics

Structural phase transition and opto-electronic properties of NaZnAs

In this study, we predict the structural phase transitions as well as opto-electronic properties of the filled-tetrahedral (Nowotny-Juza) NaZnAs compound. Calculations employ the full potential (FP) linearized augmented plane wave (LAPW) plus local orbitals (lo) scheme. The exchange-correlation potential is treated within the generalized gradient approximation of Perdew-Burke and Ernzerhof (GGA-PBE). In addition, Tran and Blaha (TB) modified Becke-Johnson (mBJ) potential is also used to obtain more accurate optoelectronic properties. Geometry optimization is performed to obtain reliable total energies and other structural parameters for each NaZnAs phase. In our study, the sequence of the structural phase transition on compression is Cu2Sb-type ? ß ? a phase. NaZnAs is a direct (G-G) band gap semiconductor for all the structural phases. However, compared to PBE-GGA, the mBJ approximation reproduces better fundamental band gaps. Moreover, for insight into its potential for photovoltaic applications, different optical parameters are studied

Special Issue on “Recent Advances in Novel Materials for Future Spintronics”

A total of 23 manuscripts were received for our Special Issue (SI), of which 7 manuscripts were directly rejected without peer review [...

Strain Conditions for the Inverse Heusler Type Fully Compensated Spin-Gapless Semiconductor Ti₂MnAl: A First-Principles Study

In this work, we systematically studied the structural, electronic, magnetic, mechanical and thermodynamic properties of the fully compensated spin-gapless inverse Heusler Ti2MnAl compound under pressure strain condition by applying the first-principles calculation based on density functional theory and the quasi-harmonic Debye model. The obtained structural, electronic and magnetic behaviors without pressure are well consistent with previous studies. It is found that the spin-gapless characteristic is destroyed at 20 GPa and then restored with further increase in pressure. While, the fully compensated ferromagnetism shows a better resistance against the pressure up to 30 GPa and then becomes to non-magnetism at higher pressure. Tetragonal distortion has also been investigated and it is found the spin-gapless property is only destroyed when c/a is less than 1 at 95% volume. Three independent elastic constants and various moduli have been calculated and they all show increasing tendency with pressure increase. Additionally, the pressure effects on the thermodynamic properties under different temperature have been studied, including the normalized volume, thermal expansion coefficient, heat capacity at constant volume, Grüneisen constant and Debye temperature. Overall, this theoretical study presents a detailed analysis of the physical properties’ variation under strain condition from different aspects on Ti2MnAl and, thus, can provide a helpful reference for the future work and even inspire some new studies and lead to some insight on the application of this material

Insight into the Topological Nodal Line Metal YB2 with Large Linear Energy Range: A First-Principles Study

The presence of one-dimensional (1D) nodal lines, which are formed by band crossing points along a line in the momentum space of materials, is accompanied by several interesting features. However, in order to facilitate experimental detection of the band crossing point signatures, the materials must possess a large linear energy range around the band crossing points. In this work, we focused on a topological metal, YB2, with phase stability and a P6/mmm space group, and studied the phonon dispersion, electronic structure, and topological nodal line signatures via first principles. The computed results show that YB2 is a metallic material with one pair of closed nodal lines in the kz = 0 plane. Importantly, around the band crossing points, a large linear energy range in excess of 2 eV was observed, which was rarely reported in previous reports that focus on linear-crossing materials. Furthermore, YB2 has the following advantages: (1) An absence of a virtual frequency for phonon dispersion, (2) an obvious nontrivial surface state around the band crossing point, and (3) small spin–orbit coupling-induced gaps for the band crossing points

L21 and XA ordering competition in titanium-based full-Heusler alloys

The site preference rule, i.e., that the atomic sites of transition-metal-elements X and Y are determined by the number of their valence electrons, has been widely used in the design of full-Heusler alloys X 2 YZ and also used to explain their properties. In this work, the most popular Ti 2 -based Heusler alloys are selected as targets to study the site preferences of their atoms by theoretical calculations. It is observed that most of them are likely to form the L2 1 -type structure instead of the XA one. The reason for the site preference is explained on the basis of the calculated charge density differences. We further prove that each alloy shows abruptly different spintronic properties, depending on its L2 1 -type or XA-type structures. This research can be regarded as a counterexample to the site preference rule and is instructive for the future design of full-Heusler alloy materials

Optical characteristics of dilute gallium phosphide bismide: promising material for near-infra photonic device applications

International audienceWe report the optical and electronic characteristics of GaP1−xBix bismide alloys with dilute composition in the cubic zinc blende crystallographic phase calculated using a scalar relativistic Full Potential Linear Augmented Plane Wave method within Density Functional Theory. The equilibrium lattice constants are calculated using the improved generalized gradient approximation of Wu and Cohen in excellent agreement with experimental values. A quasi-linear dependence of the lattice parameters on Bi composition is obtained. Electronic structures such as the band gap, total density of states and partial density of states have been discussed using the recently developed approximate modified Becke–Johnson of Tran-Blaha with spin–orbit interaction (SOI) included. Electronic band structure analysis shows a significant decrease of band gap energy when P is replaced by Bi (by ~548 meV per x = 0.062). The band gap can be tuned in the emission wavelengths range from the visible to near-infra spectrum (~0.414–1.633 μm for x ~ 0.187). The decrease in band gap energy is attributed to the both resonance interactions between Bi_p sates with the top of the valence band and Ga_s states at the host conduction band when the Bi content increased. The band gap undergoes an indirect (Γ–X) to direct (Γ–Γ) transition at x = 0.05. The complex dielectric function, refractive index, reflectivity, extinction and absorption coefficient were calculated for incident radiation energy 0–8 eV. The critical-points in various optical spectra are identified in excellent agreement with measured values. The maximum absorption occurs within the energy range from ∼5 to 8 eV, corresponding to the ultraviolet spectrum region. Dilute GaP1−xBix alloys are a promising material system for the realization of the future photonic devices operating in the near-infra spectrum

Electronic, magnetic, and thermodynamic properties of rhombohedral Dysprosium Manganite and discussions of effects of uniform strain, spin-orbit coupling, hole and electron doping on its electronic structures

In recent years, the search for new Dirac half-metallic materials has been one of the hotspots in the field of spintronics because they have very good physical properties, such as massless Dirac fermions and full spin polarization. In this study, using density function theory combined with the quasi-harmonic Debye model, we show that perovskite-type dysprosium manganite is a novel half metal with multiple Dirac cones. A detailed study of the electronic, magnetic, and thermodynamic properties of DyMnO3 was carried out. Furthermore, the effects of uniform strain, the on-site Coulomb interaction U, spin-orbit coupling, and hole and electron doping on the multiple Dirac cones and full spin polarization were investigated. We should point out that such a spin-polarized Dirac material is rare among perovskite-type compounds. Hence, we hope that, through this work, this kind of material will receive more extensive attention in future studies

Perovskite R3c phase AgCuF3: multiple Dirac cones, 100% spin polarization and its thermodynamic properties

Very recently, experimentally synthesized R3c phase LaCuO3 was studied by Zhang, Jiao, Kou, Liao & Du [J. Mater. Chem. C (2018), 6, 6132-6137], and they found that this material exhibits multiple Dirac cones in its non-spin-polarized electronic structure. Motivated by this study, the focus here is on a new R3c phase material, AgCuF3, which has a combination of multiple Dirac cones and 100% spin polarization properties. Compared to the non-spin-polarized system LaCuO3, the spin-polarized Dirac behavior in AgCuF3 is intrinsic. The effects of on-site Coulomb interaction, uniform strain and spin-orbit coupling were added to examine the stability of its multiple Dirac cones and half-metallic behavior. Moreover, the thermodynamic properties under different temperatures and pressures were investigated, including the normalized volume, thermal volume expansion coefficient, heat capacity at constant volume and Debye temperature. The thermal stability and the phase stability of this material were also studied via ab initio molecular dynamic simulations and the formation energy of the material, respectively