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The Mn3Ga material is a promising candidate for memory and computing devices owing to its rich crystalline structures of tunable ferrimagnetic and collinear and non-collinear antiferromagnetic phases. In particular, Mn3Ga with non-collinear antiferromagnetic order exhibits giant anomalous and topological Hall conductivities and is a potential material platform for hosting spin-related quantum phenomena. In this study, we demonstrate Mn3Ga films grown on thermally oxidized Si substrates, with and without the Ta buffer, under different deposition temperatures (Ts). With increasing Ts, the dominant crystalline structure across all Mn3Ga films evolves from a cubic to hybrid tetragonal and hexagonal texture, wherein the crystalline orientation of spins endows the films with in-plane magnetic anisotropy. For Ta/Mn3Ga and Mn3Ga films grown under high Ts, the inhomogeneity in surface energy of the buffer layer results in a non-uniform granular film in the former. Notably, the Mn3Ga films of hexagonal texture exhibit topological Hall signatures. The density functional theory calculations on the hexagonal Mn3Ga phase corroborated with the experimental magnetic, structural, and transport properties. These findings establish an important platform for tailoring Mn3Ga films toward multifunctional applications. [ABSTRACT FROM AUTHOR]

Potassium sodium niobate (KNN) is a lead free ceramic that can potentially replace PZT (Pb(ZrTi)O3). However, KNN suffers from a few major disadvantages. These include the presence of highly volatile alkaline elements and stoichiometry sensitive properties coupled with severe difficulties in controlling the composition. In this work, La doped sodium potassium niobate based perovskite (ABO3) ceramics, more specifically [{(1-x)(K0.5Na0.5)xLa}Nb(1–2x/5)O3] (0 < x < 0.1), have been developed. Among these, the material at 5 mol. % La doping appears with an unusually high density up to 99% of its theoretical value, while densities of the parent K0.5N0.5NbO3 (KNN) ceramics typically only reach ∼70% to 89% of the theoretical limit. The developed ceramics in their circular and rectangular disk form with thickness 0.8 mm show transparency and most importantly, this transparency is electrically tunable up to 52%. Additionally, the material shows sensitivity of its magnetic and optical properties to ultraviolet (UV) irradiation, i.e., these materials transform to a metastable and reversible state that exhibits graded color change from clear to deep blue and shows a considerable increase in magnetization under UV exposure. This feature makes the developed ceramics attractive for the fabrication of new generation devices; e.g., powerless UV detectors as well as protectors, since it absorbs UV completely. Based on first-principles calculations, we developed a model that attributes these observations to the occupancy of La fxyz orbitals induced by UV excitations. The model also indicates that UV induced absorption in the visible range and magnetism are related. [ABSTRACT FROM AUTHOR]

In this work, the spin Hall characteristics of W/CoFeB/MgO have been systematically studied to provide an in‐depth insight for the optimization of the SOT‐MRAM channel. The bcc and β phases of tungsten (W) are identified clearly from XRD and resistivity studies, which shows marked impact on the electrical characteristics. Moreover, the same is found have tremendous affect on W's spin Hall characteristics with a twelvefold increase of the spin Hall angle ΘSH. The evaluation of W/CoFeB interfacial spin mixing conductance geff↑↓ using ab initio studies shows good coherency with the same evaluated experimentally, which is used to estimate interfacial spin transparency T to accurately evaluate intrinsic spin Hall conductivity σSH of W. The findings equivocate for a strong claim on β‐W's σSH to be around −0.23 ∓ 0.03, addressing the ongoing discrepancy. Increasing boron concentration in (Co1Fe3)100−xBx and thermal annealing temperature are found to reduce ΘSH effectively which is inferred to boron diffusion toward W. Alloying of W with Ta does not necessarily enhance ΘSH, for which very optimized relative concentration and the alloy growth phase is critical. The findings can significantly contribute to the ongoing SOT‐MRAM development for achieving various means of control for improvement in the device characteristics. [ABSTRACT FROM AUTHOR]

Traditional colloidal quantum dots rely on larger‐bandgap semiconductor shells for the localization of excitons in their emissive core. Unshelled quantum dots are typically weakly luminescent due to severe quenching by deep electronic traps. Lead halide perovskite nanocrystals deviate from this convention and require only common monofunctional aliphatic ligands on their surfaces to attain near‐unity luminescence quantum yields. Here, a combination of density functional theory calculations and experimental studies is employed to elucidate the mechanistic role of the ligands. The attachment of a surface ligand leads to a distortion of the surface, which results in the localization of the valence band deeper into the subsurface layers. This creates an energetic profile that is similar to a conventional core–shell quantum dot and renders the valence electrons unavailable for interaction with adventitious chemical species. It is further shown that a phosphonate moiety offers significantly stronger binding and leads to the long‐term preservation of this beneficial subsurface localized band structure. As experimental proof, a red‐emitting mixed‐halide perovskite nanocrystal, which is usually susceptible to degradation and spectral shifts, exhibits remarkable stability under a phosphonate ligand shell. These findings and mechanistic insights may guide the future engineering of robust perovskite nanocrystals for color displays and light‐emitting applications. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of CO2 enables the utilisation and conversion of CO2 greenhouse gas into valuable fuels and chemicals. Transition metals, copper in particular, are most widely investigated as catalysts due to their ability to convert CO2 into a multitude of value-added carbon products. However, linear scaling relations prevent similarly-bound reaction intermediates (*CO, *CHO) from being stabilised independently on the surface, therefore severely limiting the activity and overpotential of transition metal catalysts. Here, we present a theoretical study of two-dimensional transition metal carbides and nitrides (MXenes) as promising electrocatalysts for the reduction of CO2 to CH4. A different CO2 reduction pathway through –H coordinated *HCOOH was discovered on O-terminated MXene catalysts due to generally weaker *CO binding. New scaling relations were established based on the alternating –C and –H coordination of the intermediates along the minimum energy pathway. Importantly, we found that the limiting potential of the MXene catalysts is determined by the binding energies of *COOH and/or *HCOOH which can be tuned independently, allowing significantly lower overpotential to be achieved compared to transition metals. In particular, two promising MXenes with theoretical overpotentials of 0.52 and 0.69 V, and competitive selectivity with respect to hydrogen evolution, were identified. [ABSTRACT FROM AUTHOR]

We present first-principles calculations of the isotropic NMR Ga shielding in metallic MGa2 with M = Ca, Sr, Ba and MGa4 with M = Na, Ca, Sr and Ba. We show that the experimentally observed trend of Ga NMR shifts is as expected driven mainly by the spin part of the response, but the orbital contribution must not be neglected. For all analyzed compounds the spin contact term constitute the major component of the response, except for BaGa2, where the spin-dipolar contribution is unusually large. This spin-dipolar contribution is related to the difference of the Ga-4pz and 4px,y partial density of states (PDOS) at the Fermi level, which is large only for BaGa2. It is related to the honeycomb-like Ga-lattice and the distances between Ga atoms. The spin-contact term is determined to a large extend by Ga-4s PDOS at the Fermi level, because the magnetic field leads to a small spin-splitting and a reoccupation of spin-up and spin-down states. This Ga-4s PDOS is related to the local atomic structure around the Ga atoms and results in fact from an overlap with the neighboring Ga-4p orbitals, therefore more symmetric local arrangements of atoms around Ga result in higher Ga-4s PDOS. However, we noticed that for very low Ga-4s PDOS the spin contact term does not tend to zero but changes sign and becomes diamagnetic. This can be explained by the energy dependence of the Ga-4s radial wave function near the nucleus, leading to a contraction/expansion of 4s densities, respectively. This effect is also present in all insulating materials; however, it has been neglected so far in literature. [ABSTRACT FROM AUTHOR]