448 research outputs found
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
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
Impact of hydrostatic pressure on superconductivity of Sr0.5La0.5FBiS2
We report the impact of hydrostatic pressure (0-1.97GPa) on superconductivity
of recently discovered 2K superconductor Sr0.5La0.5FBiS2. Resistivity under
pressure measurements are performed by using HPC-33 Piston type pressure cell
with Quantum design DC resistivity Option. The superconducting transition
temperature (Tc) is increased by 5 fold to around 10K with just above 1GPa
pressure, which remains nearly unaltered for studied higher pressures of up to
1.97GPa. The fivefold increase in Tc of Sr0.5La0.5FBiS2 with just above 1GPa
pressure suggests very strong electron correlations in these systems and the
same calls for the attention of solid state physics community.Comment: 11 pages text + Figs: Five fold increase in Tc with Just above 1GP
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