Spin and current transport in the robust half-metallic magnetc-CoFeGe

Spintronics is an emerging form of electronics based on the electrons' spin degree of freedom for which materials with robust half-metallic ferromagnet character are very attractive. Here we determine the structural stability, electronic, magnetic, and mechanical properties of the half-Heusler (hH) compound CoFeGe, in particular also in its cubic form. The first-principles calculations suggest that the electronic structure is robust with 100% spin polarization at the Fermi level under hydrostatic pressure and uni-axial strain. Both the longitudinal and Hall current polarization are calculated and the longitudinal current polarization (PL) is found to be>99%and extremely robust under uniform pressure and uni-axial strain. The anomalous Hall conductivity and spin Hall conductivity of hH cubic CoFeGe (c-CoFeGe) are found to be∼-100S cm^-1and∼39 ℏ/eS cm^-1, respectively. Moreover, the Curie temperature of the alloy is calculated to be ∼524 K with a 3μBmagnetic moment. Lastly, the calculated mechanical properties indicate thatc-CoFeGe is ductile and mechanically stable with a bulk modulus of ≈154 GPa. Overall, this analysis reveals that cubic CoFeGe is a robust half-metallic ferromagnet and an interesting material for spintronic applications.

Thermoelectric transport properties of XAgP (X = Sr and Ba) from first principles

For thermoelectric applications those materials are of interest that have significant power factor (PF) and low lattice thermal conductivity,κL. Here we theoretically exploreκLof two novel materials SrAgP and BaAgP using linearized Boltzmann transport equation with a single-mode relaxation time approach. We estimate the figure of meritzTby employingab-initiocalculations based on density functional theory and semiclassical Boltzmann transport theory. It is observed that at room temperature SrAgP exhibits slightly higher lattice thermal conductivity than BaAgP, which is mainly due to the large phonon group velocity. The relaxation time derived from deformation potential theory indicates a higherp-type PF for SrAgP compared to BaAgP over the entire temperature range. This provides an estimate for the figure of merit for the two materials. The low lattice thermal conductivity and higher PF make SrAgP a more promising thermoelectric material.

Metal-arene reduced Fe–Sb nanoparticles as a highly efficient catalyst for nitrophenol reduction

High catalytic efficiency of first time synthesised Fe–Sb alloyed NPs via sodium naphthalenide driven reduction approach.

First-principles investigations of orthorhombic-cubic phase transition and its effect on thermoelectric properties in cobalt-based ternary alloys

We screened six cobalt-based 18-VEC systems CoVSi, CoNbSi, CoTaSi (Si-group) and CoVGe, CoNbGe, CoTaGe (Ge-group) by the first-principles approach, with the motivation of stabilizing these orthorhombic phases into the cubic symmetry-favorable for thermoelectrics. Remarkably, it was found that the Ge-group is energetically more favorable in the cubic symmetry than the hitherto orthorhombic phase. We account the cubic ground state of the Si-group to the interplay of internal pressure and covalent interactions. The principle of reducing covalent interactions will provide insight and could be vital in speeding the search of missing cubic half-Heusler alloys. Meanwhile, the calculated transport properties of all the systems on p -type doping, except CoVSi, are more promising than the well-known CoTiSb. We also provide conservative estimates of the figure of merit, exceeding the CoTiSb. Based on our findings, we suggest possible new phases of ternary compounds for thermoelectric applications.

First-principles study of thermoelectric properties of Li-based Nowotony-Juza phases

We investigated the cubic-hexagonal phase transition and its effect on thermoelectric performance in Li-based Nowotny-Juza phases LiZn X (X  =  N, P, As, Sb, and Bi). Interestingly, other than LiZnSb, the cubic LiZnBi is found to be energetically more favorable than the hitherto reported hexagonal phase. The hexagonal phases of reported cubic LiZnP and LiZnAs are likely to be stabilized by pressure-hydrostatic pressure can be aided by internal pressure. We find that while power factor values are much improved in the proposed hexagonal phases, the values in cubic phases are also impressive. We also determine conservative estimates of the figure of merit. The ZT values of cubic and hexagonal LiZnSb at 700 K are 1.27 and 1.95, respectively. Other promising values are 1.96 and 1.49 at 700 K of hexagonal n-type LiZnP and LiZnAs, respectively. Overall, our findings suggest the good thermoelectric potential of Nowotny-Juza phases.

J_{eff} Description of the Honeycomb Mott Insulator α-RuCl_{3}

Novel ground states might be realized in honeycomb lattices with strong spin-orbit coupling. Here we study the electronic structure of α-RuCl_{3}, in which the Ru ions are in a d^{5} configuration and form a honeycomb lattice, by angle-resolved photoemission, x-ray photoemission, and electron energy loss spectroscopy supported by density functional theory and multiplet calculations. We find that α-RuCl_{3} is a Mott insulator with significant spin-orbit coupling, whose low energy electronic structure is naturally mapped onto J_{eff} states. This makes α-RuCl_{3} a promising candidate for the realization of Kitaev physics. Relevant electronic parameters such as the Hubbard energy U, the crystal field splitting 10 Dq, and the charge transfer energy Δ are evaluated.

Experimental study on modulation of Stokes parameters on propagation of a Gaussian Schell model beam in free space

The effect on the Stokes parameters of a Gaussian Schell model beam on propagation in free space is studied experimentally and results are matched with the theory [X. H. Zhao, et al. Opt. Express 17, 17888 (2009)] that in general the degree of polarization of a Gaussian Schell model beam doesn't change on propagation if the three spectral correlation widths δ xx, δ yy, δ xy are equal and the beam width parameters σ x =σ y. It is experimentally shown that all the four Stokes parameters at the center of the beam decrease on propagation while the magnitudes of the normalized Stokes parameters and the spectral degree of polarization at the center of the beam remain constant for different propagation distances.

Effect of surface plasmons on spectral switching of polychromatic light with Au-double-slit

It is shown that the generation of surface plasmons on a metal-dielectric interface, i.e., a Au-double-slit and air interface, appreciably affects the intensity of the diffracted light. With a specific example of Au-double-slit and electro-optic devices before the slits, the spectral switching in the diffracted field with the polychromatic light is shown for the first time, to our knowledge. It is found that at the observation point due to the surface plasmon effect the intensity of the diffracted light periodically increases and decreases with the separation of the double-slit.

Revision of model parameters for kappa-type charge transfer salts: an ab initio study

Intense experimental and theoretical studies have demonstrated that the anisotropic triangular lattice as realized in the kappa-(BEDT-TTF)2X family of organic charge transfer salts yields a complex phase diagram with magnetic, superconducting, Mott insulating, and even spin liquid phases. With extensive density functional theory calculations we refresh the link between many body theory and experiment by determining hopping parameters of the underlying Hubbard model. This leads us to revise the widely used semiempirical parameters in the direction of less frustrated, more anisotropic triangular lattices. The implications of these results on the systems' description are discussed.

Experimental study of the phenomenon of 1 x N spectral switch due to diffraction of partially coherent light

Spectral properties of a class of partially coherent light with spectral profiles of varying bandwidths are studied on diffraction by a circular aperture in the far zone for different diffractive angles, i.e., for on-axis and off-axis points on the observation plane. It is found that the spectrum of the light in the far zone is different from that at the aperture plane. This change in the spectrum is termed spectral shift, which is found to be different at different diffractive angles. The spectral shift for a fixed diffactive angle shows a gradual change. However, for a critical value of the coherence at the aperture plane, the spectral shift shows a rapid transition, termed spectral switch. For different diffractive angles the coherence that causes the spectral switch also differs. Therefore the phenomenon of 1 x N spectral switch (consisting of one input port and N output ports) is studied experimentally.

Spectral shift due to source correlation in conventional spectroradiometric measurements

Keeping in view the recent findings of the spectral shift due to source correlation during propagation of light, a study has been undertaken to analyze the errors which may be introduced in spectroradiometric measurements.