In this paper, we report the signature of spin gapless semiconductor (SGS) in CoFeMnSi that belongs to the Heusler family. SGS is a new class of magnetic semiconductors which have a band gap for one spin subband and zero band gap for the other, and thus are useful for tunable spin transport based applications. We show various experimental evidences for SGS behavior in CoFeMnSi by carefully carrying out the transport and spin-polarization measurements. SGS behavior is also confirmed by first-principles band-structure calculations. The most stable configuration obtained by the theoretical calculation is verified by experiment. The alloy is found to crystallize in the cubic Heusler structure (LiMgPdSn type) with some amount of disorder and has a saturation magnetization of 3.7 μ B /f.u. and Curie temperature of ∼620 K. The saturation magnetization is found to follow the Slater-Pauling behavior, one of the prerequisites for SGS. Nearly-temperature-independent carrier concentration and electrical conductivity are observed from 5 to 300 K. An anomalous Hall coefficient of 162 S/cm is obtained at 5 K. Point contact Andreev reflection data have yielded the current spin-polarization value of 0.64, which is found to be robust against the structural disorder. All these properties strongly suggest SGS nature of the alloy, which is quite promising for the spintronic applications such as spin injection as it can bridge the gap between the contrasting behaviors of half-metallic ferromagnets and semiconductors.

[1] Measurements are reported of particle number concentration at two urban sites within Birmingham, UK. The measurements were made with a condensation particle counter (TSI Model 3022A) and an ultrafine particle counter (TSI Model 3025) operated in tandem. Other colocated measurements included particle surface area by epiphaniometer, sulfur dioxide, oxides of nitrogen and ozone, solar radiation or J O 1 D , and in some campaigns, particle number size distribution by Scanning Mobility Particle Sizer. Events were identified when substantial excursions in particle number count were accompanied by a divergence between the two particle counters indicating a large number of particles in the 3-7 nm diameter range. Criteria have been developed to distinguish between particles within this size range arising from homogeneous nucleation within the atmosphere and from emissions from point sources. Out of a total of 232 days sampling distributed throughout the year, events on only 8 days could be attributed fairly unequivocally to homogeneous nucleation processes, with a further 4 days possibly attributable. Nucleation events occur in winter as well as summer months, but depend, among other things, upon a low particle surface area. Modeling of aerosol dynamical processes for 20 June 1999, indicates that the observations can be explained by a nucleation rate of 6 Â 10 6 cm À3 s À1 at a condensable vapor concentration (as H 2 SO 4 ) of 6.5 Â 10 7 cm À3 . It is inferred that both the nucleation and particle growth processes involve condensable molecules other than, or in addition to, sulfuric acid.

Formation energies of native defects in Bi 2 (Te x Se 3−x), with comparison to ideal Bi 2 Te 2 S, are calculated in density-functional theory to assess transport properties. Bi 2 Se 3 is found to be n type for both Bi-and Se-rich growth conditions, while Bi 2 Te 3 changes fromn to p type going from Te-to Bi-rich conditions, as observed. Bi 2 Te 2 Se and Bi 2 Te 2 S are generally n type, explaining observed heavily doped n-type behavior in most samples. A (0/−) transition level at 16 meV above valence-band maximum for Bi on Te antisites in Bi 2 Te 2 Se is related to the observed thermally active transport gap causing a p-ton transition at low temperature. Bi 2 (Te x Se 3−x) with x>2 are predicted to have high bulk resistivity due to effective carrier compensation when approaching the n-to-pcrossover. Predicted behaviors are confirmed from characterization of our grown single crystals.

Despite a plethora of materials suggested for spintronic applications, a new class of materials has emerged, namely spin gapless semiconductors (SGS) that offers potentially more advantageous properties than existing ones. These magnetic semiconductors exhibit a finite band gap for one spin channel and a closed gap for the other. Here, supported by electronicstructure calculations, we report the first experimental evidence of SGS behavior in equiatomic quaternary CoFeCrGa, having a cubic Heusler (prototype LiMgPdSn) structure but exhibiting chemical disorder (DO 3 structure). CoFeCrGa is found to transform from SGS to half-metallic phase under pressure, which is attributed to unique electronic-structure features. The saturation magnetization (M S ) obtained at 8 K agrees with the Slater-Pauling rule and the Curie temperature (T C ) is found to exceed 400 K. Carrier concentration (up to 250 K) and electrical conductivity are observed to be nearly temperature independent, prerequisites for SGS. The anomalous Hall coefficient is estimated to be 185 S/cm at 5 K.Considering the SGS properties and high T C , this material appears to be promising for spintronic applications.

Recently, lead free all-inorganic double perovskites have revolutionized photovoltaic research, showing promising light emitting efficiency and tunability via modification of inherent structural and chemical properties. Here, we report a combined experimental and theoretical study on the variation of carrier–lattice interaction and optoelectronic properties of Cs2AgIn1–x Bi x Cl6 double perovskite nanocrystals with varying alloying concentrations. Our UV–vis study confirms the parity allowed first direct transition for x ≤ 0.25. Using a careful analysis of Raman spectra assisted with first-principles simulations, we assign the possible three types of active modes to intrinsic atomic vibrations; 2 T2g modes (one for translational motion of “Cs” and other for octahedral breathing), 1 Eg and 1 A1g mode for various stretching of Ag–Cl octahedra. Ab-initio simulation reveals dominant carrier-phonon scattering via Fröhlich mechanism near room temperature, with longitudinal optical phonons being effectively activated around 230 K. We observe a noticeable increase in hole mobility (∼4 times) with small Bi alloying, attributed to valence band (VB) maxima acquiring Bi-s orbital characteristics, thus resulting in a dispersive VB. We believe that our results should help to gain a better understanding of the intrinsic electronic and lattice dynamical properties of these compounds and provide a base toward improving the overall performance of double perovskite nanocrystals.