Hydrostatic pressure effect on Tc of new BiS2 based Bi4O4S3 and NdO0.5F0.5BiS2 layered superconductors

We investigate the external hydrostatic pressure effect on the superconducting transition temperature (Tc) of new layered superconductors Bi4O4S3 and NdO0.5F0.5BiS2. Though the Tc is found to have moderate decrease from 4.8 K to 4.3 K (dTconset/dP = -0.28 K/GPa) for Bi4O4S3 superconductor, the same increases from 4.6 K to 5 K (dTconset/dP = 0.44 K/GPa) upto 1.31 GPa followed by a sudden decrease from 5 K to 4.7 K upto 1.75 GPa for NdO0.5F0.5BiS2 superconductor. The variation of Tc in these systems may be correlated to increase or decrease of the charge carriers in the density of states under externally applied pressure.Comment: 3 pages text +Fig

Suitability of Clustering Algorithms for Crime Hotspot Analysis

Abstract-Crime analysis is a field that needs immediate attention due to the drastic increase of number of crimes. Most of the crimes, from the past experiences of the police, are said to be concentrated in some areas, called hotspots and keep on recurring. Clustering algorithms are best applied to crime analysis, but suitability of broad spectrum of clustering algorithm for an application is an issue to be addressed. In this paper we evaluate three clustering algorithms i.e. hierarchical clustering, k-means clustering and DBSCAN clustering with the intent of finding the best one suitable for crime hotspot analysis. Each one of the clustering algorithm evaluated here need inputs such as number of clusters, neighbour distance, minimum number of points etc. are needed by a cluster. The cluster similarity measure is the Euclidean distance. The results suggest that DBSCAN is much more suitable to crime hotspot analysis due to its inherent nature of being density driven

Structural and magnetic properties of CuFe₂O₄ as-prepared and thermally treated spinel nanoferrites

124-130The copper based CuFe2O4 nanoferrite was prepared by chemical co-precipitation method and the detailed investigation of structural and magnetic properties was carried out successfully at room temperature. The obtained results from XRD confirm that CuFe2O4 has tetragonal structure at room temperature and its crystallite size, lattice strain was found to be varied from 11 to 17 nm and <span style="mso-bidi-font-weight: bold">3.910-2 to 2.610-2 for microwave annealed to as-prepared samples calculated using Scherrer equation and Williamson-Hall analysis, respectively. A clear superparamagnetic behaviour was observed in as-prepared and hot air oven annealed nanoferrite samples at RT under the field range of ±2 T. A distorted superparamagnetic curve was determined from isothermal magnetic hysteresis studies for the microwave oven annealed sample. It might be a possible magnetic and non-magnetic cation transformation on the surface of CuFe2O4 nanoparticles along with high lattice strain resulting in change of magnetic properties under certain level of applied magnetic field. </span

Critical behavior of resistivity in the pressure-induced first to second order transition in Pr0.6Ca0.4Mn0.96B0.04O3(B = Co and Cr)

10.1016/j.jallcom.2014.08.112Journal of Alloys and Compounds618159-16

Enhanced upper critical field, critical current density, and thermal activation energy in new ytterbium doped CeFeA_0.9F_0.1 superconductor

In this report, we have investigated the essential physical properties of Ce_0.7Yb_0.3FeAsO_0.9F_0.1 superconductor such as field dependent critical current density (J_c), thermal activation energy (U₀), and upper critical field (H_c2). From the isothermal magnetization curves and size of the superconducting grains, the critical current density J_c of 2.3 × 10⁶ A/cm² at 2 K, 0.5 T was estimated using the Bean's model for this Yb doped superconductor. A gradual decrease of J_c and absence of peak effect were found on increasing magnetic field up to 5 T. Thermal activation energy (U₀/k_B = ∼2500 K) calculated from Arrhenius plots at low magnetic field (0.5 T) indicates a strong flux pinning potential might be co-existing with applied magnetic field. Our results suggest that this new Yb doped superconductor is a possible practical high temperature superconductor under certain magnetic field and temperature

Superconductivity in La_1−xSm_xO_0.5F_0.5BiS₂(x = 0.2, 0.8) under hydrostatic pressure

We have investigated the pressure effect on the newly discovered samarium-doped La_1−xSm_xO_0.5F_0.5BiS₂ superconductors. More than a threefold increase in T_c (10.3 K) is observed with external pressure (at ~1.74 GPa at a rate of 4.08 K GPa⁻¹) for x  =  0.2 composition. There is a concomitant large improvement in the quality of the superconducting transition. Beyond this pressure T_c decreases monotonously at the rate of −2.09 K GPa⁻¹. In the x  =  0.8 sample, we do not observe any enhancement in T_c with the application of pressure (up to 1.76 GPa). The semiconducting behavior observed in the normal-state resistivity of both samples is significantly subdued with the application of pressure which, if interpreted by invoking the thermal activation process, implies that the activation energy gap of the carriers is significantly reduced with pressure. We believe these observations should generate further interest in La_1−xSm_xO_0.5F_0.5BiS₂ superconductors