Superconductivity at 5K in NdO0.5F0.5BiS2

We report appearance of superconductivity at 5K in NdO0.5F0.5BiS2 and supplement the discovery [1] of the same in layered sulfide based ZrCuSiAs type compounds. The bulk polycrystalline compound is synthesized by conventional solid state route via vacuum encapsulation technique. Detailed structural analysis showed that the studied compound is crystallized in tetragonal P4/nmm space group with lattice parameters a = 3.9911(3) {\AA}, c = 13.3830(2) {\AA}. Bulk superconductivity is established in NdO0.5F0.5BiS2 at 5K by both transport and magnetic measurements. Electrical transport measurements showed superconducting Tc onset at 5.2K and Tc ({\rho}=0) at 4.7K. Under applied magnetic field both Tc onset and Tc ({\rho} =0) decrease to lower temperatures and an upper critical field [Hc2(0)] of above 23kOe is estimated. Both AC and DC magnetic susceptibility measurements showed bulk superconductivity below 5K. Isothermal magnetization (MH) exhibited typical type II behavior with lower critical field (Hc1) of around 15Oe. Isothermal magnetization (MH) exhibited typical type-II behavior with lower critical field (Hc1) of around 15Oe. Specific heat [Cp(T)] is investigated in the temperature range of 1.9-50K in zero external magnetic field. A Schottky-type anomaly is observed at low temperature below 7K. This low temperature Schottky can be attributed to the change in the entropy of the system.Comment: 10 pages text + Figs (New Version):comments/suggestion welcome ([email protected]

Synthesis and superconductivity of new BiS2 based superconductor PrO0.5F0.5BiS2

We report synthesis and superconductivity at 3.7K in PrO0.5F0.5BiS2. The newly discovered material belongs to the layered sulfide based REO0.5F0.5BiS2 compounds having ZrCuSiAs type structure. The bulk polycrystalline compound is synthesized by vacuum encapsulation technique at 7800C in single step. Detailed structural analysis has shown that the as synthesized PrO0.5F0.5BiS2 is crystallized in tetragonal P4/nmm space group with lattice parameters a = 4.015(5) {\AA}, c = 13.362(4) {\AA}. Bulk superconductivity is observed in PrO0.5F0.5BiS2 below 4K from magnetic and transport measurements. Electrical transport measurements showed superconducting transition temperature (Tc) onset at 3.7K and Tc ({\rho}=0) at 3.1K. Hump at Tc related to superconducting transition is not observed in heat capacity measurement and rather a Schottky-type anomaly is observed at below ~6K. The compound is slightly semiconducting in normal state. Isothermal magnetization (MH) exhibited typical type II behavior with lower critical field (Hc1) of around 8Oe.Comment: Short note 10 pages text+figs. First report on PrO.5F.5BiS2 Su

Superconducting Mechanism through direct and redox layer doping in Pnictides

The mechanism of superconductivity in pnictides is discussed through direct doping in superconducting FeAs and also in charge reservoir REO layers. The un-doped SmFeAsO is charge neutral SDW (Spin Density Wave) compound with magnetic ordering below 150 K. The Superconducting FeAs layers are doped with Co and Ni at Fe site, whereas REO layers are doped with F at O site. The electron doping in SmFeAsO through Co results in superconductivity with transition temperature (Tc) maximum up to 15 K, whereas F doping results in Tc upto 47 K in SmFeAsO. All these REFe/Co/NiAsO/F compounds are iso-structural to ZrCuSiAs structure. The samples are crystallized in a tetragonal structure with space group P4/nmm. Variation of Tc with different doping routes shows the versatility of the structure and mechanism of occurrence of superconductivity. It seems doping in redox layer is more effective than direct doping in superconducting FeAs layer.Comment: 4 Pages text + Figs: ([email protected]

Bulk Superconductivity in Bismuth-oxy-sulfide Bi4O4S3

Very recent report [1] on observation of superconductivity in Bi4O4S3 could potentially reignite the search for superconductivity in a broad range of layered sulphides. We report here synthesis of Bi4O4S3 at 5000C by vacuum encapsulation technique and basic characterizations. Detailed structural, magnetization, and electrical transport results are reported. Bi4O4S3 is contaminated by small amounts of Bi2S3 and Bi impurities. The majority phase is tetragonal I4/mmm space group with lattice parameters a = 3.9697(2){\AA}, c = 41.3520(1){\AA}. Both AC and DC magnetization measurements confirmed that Bi4O4S3 is a bulk superconductor with superconducting transition temperature (Tc) of 4.4K. Isothermal magnetization (MH) measurements indicated closed loops with clear signatures of flux pinning and irreversible behavior. The lower critical field (Hc1) at 2K, of the new superconductor is found to be ~39 Oe. The magneto-transport R(T, H) measurements showed a resistive broadening and decrease in Tc (R=0) to lower temperatures with increasing magnetic field. The extrapolated upper critical field Hc2(0) is ~ 310kOe with a corresponding Ginzburg-Landau coherence length of ~100{\AA} . In the normal state the {\rho} ~ T2 is not indicated. Our magnetization and electrical transport measurements substantiate the appearance of bulk superconductivity in as synthesized Bi4O4S3. On the other hand same temperature heat treated Bi is not superconducting, thus excluding possibility of impurity driven superconductivity in the newly discovered Bi4O4S3 superconductor.Comment: 12 pages Text + Fig

Anti-inflammatory and ulcerogenic activities of thiazolidine-4-ones in rats

Background: NSAIDS are associated with side effects and research should continue for developing safer drugs. This study aims to evaluate newer thiazolidine-4-ones for their anti-inflammatory and ulcerogenic activities in wister rats.Methods: Five groups of wister rats, 6 in each were used.  Anti-inflammatory and ulcerogenic activities of diclofenac (30mg/kg), nimesulide (50mg/kg), thia-1 (50mg/kg) and thia-2 (50mg/kg) are compared with control group (4% Gum Acacia). Carrageenin-induced paw edema, formaline induced acute peritonitis and cotton pellet-induced granulomatous tissue formation models were used for evaluating anti-inflammatory activity. After removing cotton pellets with granuloma on 8th day gastric ulcerogenicity was assessed by using macroscopic and microscopic scoring of ulcers.Results: Diclofenac, nimesulide and thia 2 reduced both paw edema and peritoneal exudate volume significantly (p 0.05). Nimesulide, thia-1 and thia-2 did not increase gastric ulcer score significantly (p >0.05). Diclofenac increased ulcer score significantly (p <0.01).Conclusions: Thia-2 demonstrated significant anti-inflammatory activity in acute and chronic models. In addition to inhibition of cyclooxygenase pathway, PPAR agonistic activity may be involved in its anti-inflammatory activity.  No significant ulcerogenicity was observed on comparing with nimesulide and control. Further in-vitro and in-vivo studies are recommended to confirm the results of this study

Magnetization and Magneto-resistance in Y(Ba1-xSrx)2Cu3O7-{\delta} (x = 0.00 - 0.50) superconductor

Here we present the magnetic properties and upper critical field (BC2) of polycrystalline Y(Ba1-xSrx)2Cu3O7-{\delta} superconductors, which are being determined through detailed ac/dc susceptibility and resistivity under magnetic field (RTH) study. All the samples are synthesized through solid state reaction route. Reduction in Meissner fraction (the ratio of field cooled to zero field cooled magnetization) is observed with increasing Sr content, suggesting occurrence of flux pining in the doped samples. The ac susceptibility and resistivity measurements reveal improved grain couplings in Sr substituted samples. Consequently the inter-grain critical current density (Jc), upturn curvature near the Tc in temperature dependence of upper critical field [BC2(T)], and BC2 are enhanced. Both Jc and BC2 increase in lower Sr substitution (up to x = 0.10) samples followed by decrease in higher doping due to degradation in effective pining and grain coupling.Comment: 17 pages text + Figs, [email protected]