Short Note on Superconductivity at Ambient Temperature and Pressure in Silver Embedded Gold Nano-particles: A Goldsmith job ahead

Very recent observation of superconductivity in both transport (resistance versus temperature) and magnetization (Zero field cooled) at around 235 K has obviously raised many eyebrows. The experimental fraternity in particular is more thrilled. Although the results presented in the paper are clean and both transport and magnetization measurements do approve the observation of superconductivity to some extent (the shielding fraction is low), the problem is to synthesize or fabricate the material. This I name a goldsmith job, primarily because one has to deal with Gold and Silver nano particles combination/amalgamation/alloying or even who knows the inter-facial new phase, which could be superconducting. This short note is written in view to let the spark continues and the interesting work of ) authors is reproduced independently.Comment: 3 Pages text: Accepted Letter J. Sup. & Novel Ma

Effect of Se doping in recently discovered layered Bi4O4S3 Superconductor

We report suppression of superconductivity in Bi4O4S3 compound by Se doping at S site. Bulk polycrystalline samples are synthesized by solid state reaction route. The Rietveld refined of XRD data of all the studied samples show that the same are crystallized in tetragonal I4/mmm space group with slightly increased c lattice constant with the Se doping. Superconductivity is observed at below 4.5 K in both dc magnetization and resistivity with temperature measurements for all Bi4O4S3-xSex (x = 0, 0.03, 0.09 and 0.15) samples, though the same is decreased slightly with increase in Se content. The upper critical field of the Bi4O4S3 is estimated from resistivity under magnetic field [R(T)H] measurements of up to 2T (Tesla), and the same decreases for Se doped samples. The flux flow activation energies being obtained by fitting to the the Arrhenius equation are 18.60 meV for Bi4O4S3, 13.69 meV for Bi4O4S2.97Se0.03 and 13.16 meV for Bi4O4S2.85Se0.15 samples in applied magnetic field of 200 Oe. In conclusion the S site Se substitution showed detrimental effect on superconductivity of Bi4O4S3.Comment: 9 pages text + Fig

Superconductivity in layered CeO0.5F0.5BiS2

We report appearance of superconductivity in CeO0.5F0.5BiS2. The bulk polycrystalline samples CeOBiS2 and CeO0.5F0.5BiS2 are synthesized by conventional solid state reaction route via vacuum encapsulation technique. Detailed structural analysis showed that the studied CeO0.5F0.5BiS2 compound is crystallized in tetragonal P4/nmm space group with lattice parameters a = 4.016(3) A, c = 13.604(2) A. DC magnetization measurement (MT-curve) shows the ferromagnetic signal at the low temperature region. The superconductivity is established in CeO0.5F0.5BiS2 at Tconset = 2.5K by electrical transport measurement. Under applied magnetic field both Tc onset and Tc ({\rho} =0) decrease to lower temperatures and an upper critical field [Hc2(0)] above 1.2Tesla is estimated. The results suggest coexistence of ferromagnetism and superconductivity for the CeO0.5F0.5BiS2 sample.Comment: 9 pages text + Fig

High pressure high temperature (HPHT) synthesis and magnetization of Magneto-Superconducting RuSr2(LnCe2)Cu2O12.25 (Ru-1232) compounds (Ln = Y and Dy)

RuSr2(LnCe2)Cu2O12.25 (Ru-1232) compounds with Ln = Y and Dy being synthesized by high pressure high temperature (6GPa, 12000C) solid state synthesis route do crystallize in space group P4/mmm in near single phase form with small quantities of SrRuO3 and RuSr2(RE1.5Ce0.5)Cu2O10 (Ru-1222). Both samples exhibit magnetic transitions (Tmag.) at ~90 K with significant branching of zfc (zero-field-cooled) and fc (field-cooled) magnetization and a sharp cusp in zfc at ~ 70 K, followed by superconducting transitions at ~ 30 K. Both compounds show typical ferromagnetic hysteresis loops in magnetic moment (M) versus field (H) magnetization right upto Tmag. i.e. < 90K. To our knowledge these are the first successfully synthesized Ru-1232 compounds in near single phase with lanthanides including Y and Dy. The results are compared with widely reported Gd/Ru-1222 and Ru-1212 (RuSr2GdCu2O8) compounds. In particular, it seems that the Ru moments magnetic ordering temperature (Tmag.) scales with the c-direction distance between magnetic RuO6 octahedras in Ru-1212/1222 or 1232 systems.Comment: 15 pages of TEXT and Fig

Magnetotransport studies of FeSe under hydrostatic pressure

The discoveries of iron-based superconductors with relatively high transition temperature are under intense experimental and theoretical investigation. Here we present magnetotransport measurements on FeSe superconductor under hydrostatic pressure. We show that in Fe-deficient tetragonal FeSe binary compound, the onset of superconducting transition is almost doubled under 1.98GPa pressure and the estimated upper critical field of 26.7Tesla is increased to 47.5Tesla.Comment: Short MS: 8 pages Text + Figs. Pressure induced increase in Tc and pinnin

Appearance of bulk Superconductivity under Hydrostatic Pressure in Sr0.5RE0.5FBiS2 (RE = Ce, Nd, Pr and Sm) compounds

We report the appearance of superconductivity under hydrostatic pressure (0.35 to 2.5GPa) in Sr0.5RE0.5FBiS2 with RE = Ce, Nd, Pr and Sm. The studied compounds, synthesized by solid state reaction route, are crystallized in tetragonal P4/nmm space group. At ambient pressure though the RE = Ce exhibit the onset of superconductivity below 2.5K, the Nd, Pr and Sm samples are not superconducting down to 2K. With application of hydrostatic pressure (up to 2.5GPa), superconducting transition temperature is increased to around 10K for all the studied samples. The magneto-transport measurements are carried out on all the samples with maximum Tc i.e., at under 2.5GPa pressure and their upper critical fields are determined. The new superconducting compounds appear to be quite robust against magnetic field but within Pauli paramagnetic limit. The new superconducting compounds with various RE (Ce, Nd, Pr and Sm) belonging to Sr0.5La0.5FBiS2 family are successfully synthesized for the first time and superconductivity is induced in them under hydrostatic pressure.Comment: 17 pages text + Figs: First report on Sr0.5(Ce/Nd/Pr/Sm)0.5FBiS2 new compounds superconducting under pressur

Evolution of superconductivity in PrFe1-xCoxAsO with x = 0.0 to 1.0

We report the synthesis and physical property characterization of PrFe1-xCoxAsO with x = 0.0 to 1.0. The studied samples are synthesized by solid state reaction route via vacuum encapsulation method. The pristine compound PrFeAsO does not show superconductivity, but rather exhibits a metallic step like transition due to spin density wave ordering of Fe moments below 150 K, followed by another upward step due to anomalous ordering of Pr moments at 12 K. Both the Fe-SDW and Pr-TN temperatures decrease monotonically with Co substitution at Fe site. Superconductivity appears in a narrow range of x from 0.07 to 0.25 with maximum Tc at 11.12 K for x = 0.15. Samples, with x = 0.25 exhibit metallic behavior right from 300 K down to 2 K, without any Fe-SDW or Pr-TN steps in resistivity. In fact, though Fe-SDW decreases monotonically, the Pr-TN is disappeared even with x = 0.02. The magneto transport measurements below 14 Tesla on superconducting polycrystalline Co doped PrFeAsO lead to extrapolated values of the upper critical fields [Hc2(0)] of up to 60 Tesla.Comment: 15 pages Text+Fig