3,482 research outputs found

    Electronic reconstruction and enhanced superconductivity at La1.6x_{1.6-x}Nd0.4_{0.4}Srx_{x}CuO4_{4}/La1.55_{1.55}Sr0.45_{0.45}CuO4_{4} bilayer interface

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    We report enhanced superconductivity in bilayer thin films consisting of superconducting La1.6x_{1.6-x}Nd0.4_{0.4}Srx_{x}CuO4_{4} with 0.06 x<\leq x< 0.20 and metallic but non-superconducting La1.55_{1.55}Sr0.45_{0.45}CuO4_{4}. These bilayers show a maximum increase in superconducting transition temperature (TcT_c) of more than 200% for xx = 0.06 while no change in TcT_c is observed for the bilayers with xx\geq 0.20. The analysis of the critical current and kinetic inductance data suggests 2-3 unit cells thick interfacial layer electronically perturbed to have a higher TcT_c. A simple charge transfer model with cation intermixing explains the observed TcT_c in bilayers. Still the unusually large thickness of interfacial superconducting layers can not be explained in terms of this model. We believe the stripe relaxation as well as the proximity effect also influence the superconductivity of the interface

    Strain induced magnetic domain evolution and spin re-orientation transition in epitaxial manganite films

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    The evolution of magnetic domain structure in epitaxial La0.625_{0.625}Ca0.375_{0.375}MnO3_3 films on (001) NdGaO3_3 is monitored as a function of temperature and magnetic field using Magnetic Force Microscopy. We see two distinct regions of magnetic orientational order; one in-plane displaying contrast-less image and the other tilted away from the film plane forming a distinct stripe pattern. A strong domain splitting is observed at the boundary of two regions, which is resilient to reorientation with temperature and magnetic field. We propose a model magnetic free energy functional to explain the mechanism of domain splitting seen in manganite films

    Interface superconductivity in La1.48_{1.48}Nd0.4_{0.4}Sr0.12_{0.12}CuO4_{4}/La1.84_{1.84}Sr0.16_{0.16}CuO4_{4} bilayers

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    We identify a distinct superconducting phase at the interface of a La1.48_{1.48}Nd0.4_{0.4}Sr0.12_{0.12}CuO4_4 (LNSCO)/La1.84_{1.84}Sr0.16_{0.16}CuO4_4 (LSCO) epitaxial bilayer system using ac screening measurements. A model based on inter-diffusion of quasiparticles and condensate at the interface yields a thickness of \sim 25 nm for the interfacial layer. Two-dimensional superconductivity of the interface layer appears to be governed by Kosterlitz-Thouless-Berezinskii transition. A parallel magnetic field suppresses the superconducting transition temperature of this layer with a pair breaking parameter α\alpha varying as H2H^2

    Two-dimensional electron-gas-like charge transport at magnetic Heusler alloy-SrTiO3_3 interface

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    We report remarkably low residual resistivity, giant residual resistivity ratio, free-electron-like Hall resistivity and high mobility (\approx 104^4 cm2^2V1^{-1}s1^{-1}) charge transport in epitaxial films of Co2_2MnSi and Co2_2FeSi grown on (001) SrTiO3_3. This unusual behavior is not observed in films deposited on other cubic oxide substrates of comparable lattice parameters. The scaling of the resistivity with thickness of the films allow extraction of interface conductance, which can be attributed to a layer of oxygen vacancies confined within 1.9 nm of the interface as revealed by atomically resolved electron microscopy and spectroscopy. The high mobility transport observed here at the interface of a fully spin polarized metal is potentially important for spintronics applications

    Genetic Variation and Population Structure in Jamunapari Goats Using Microsatellites, Mitochondrial DNA, and Milk Protein Genes

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    Jamunapari, a dairy goat breed of India, has been gradually declining in numbers in its home tract over the years. We have analysed genetic variation and population history in Jamunapari goats based on 17 microsatellite loci, 2 milk protein loci, mitochondrial hypervariable region I (HVRI) sequencing, and three Y-chromosomal gene sequencing. We used the mitochondrial DNA (mtDNA) mismatch distribution, microsatellite data, and bottleneck tests to infer the population history and demography. The mean number of alleles per locus was 9.0 indicating that the allelic variation was high in all the loci and the mean heterozygosity was 0.769 at nuclear loci. Although the population size is smaller than 8,000 individuals, the amount of variability both in terms of allelic richness and gene diversity was high in all the microsatellite loci except ILST 005. The gene diversity and effective number of alleles at milk protein loci were higher than the 10 other Indian goat breeds that they were compared to. Mismatch analysis was carried out and the analysis revealed that the population curve was unimodal indicating the expansion of population. The genetic diversity of Y-chromosome genes was low in the present study. The observed mean M ratio in the population was above the critical significance value (Mc) and close to one indicating that it has maintained a slowly changing population size. The mode-shift test did not detect any distortion of allele frequency and the heterozygosity excess method showed that there was no significant departure from mutation-drift equilibrium detected in the population. However, the effects of genetic bottlenecks were observed in some loci due to decreased heterozygosity and lower level of M ratio. There were two observed genetic subdivisions in the population supporting the observations of farmers in different areas. This base line information on genetic diversity, bottleneck analysis, and mismatch analysis was obtained to assist the conservation decision and management of the breed

    Experimental studies on effect of speaking mode on spoken term detection

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    The objective of this paper is to study the effect of speaking mode on spoken term detection (STD) system. The experiments are conducted with respect to query words recorded in isolated manner and words cut out from continuous speech. Durations of phonemes in query words greatly vary between these two modes. Hence pattern matching stage plays a crucial role which takes care of temporal variations. Matching is done using Subsequence dynamic time warping (DTW) on posterior features of query and reference utterances, obtained by training Multilayer perceptron (MLP). The difference in performance of the STD system for different phoneme groupings (45, 25, 15 and 6 classes) is also analyzed. Our STD system is tested on Telugu broadcast news. Major difference in STD system performance is observed for recorded and cut-out types of query words. It is observed that STD system performance is better with query words cut out from continuous speech compared to words recorded in isolated manner. This performance difference can be accounted for large temporal variations