10,030 research outputs found
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
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
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
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
AC susceptibility study of superconducting YBa2Cu3O7:Agx bulk composites (x = 0.0-0.20): The role of intra and inter granular coupling
We report the effect of silver addition on superconducting performance of
bulk YBCO (YBa2Cu3O7) superconductor. All the studied samples are prepared by
conventional solid-state reaction method. Rietveld fitted X-ray diffraction
data confirmed the single phase formation for all the studied samples. Detailed
AC susceptibility measurements as a function of driven AC amplitude (1Oe-17Oe)
of these samples revealed the enhancement of grains coupling with increasing Ag
content in YBCO+Agx composite system. 10wt% Ag added YBCO superconductors
exhibited the optimum inter granular coupling. The Scanning Electron Microscopy
(SEM) observations indicate an increase in the grains connectivity in terms of
narrow grain boundaries for doped samples. The average grain size is found to
increase with Ag doping. It is concluded that limited addition of Ag in bulk
YBCO superconductor significantly improves the grains coupling and as result
optimum superconducting performance. YBCO+Ag composites could prove to be
potential candidates for bulk superconducting applications of the studied high
Tc system.Comment: 15 pages of text + Fig
Impact of Gd doping on morphology and superconductivity of NbN sputtered thin films
We report effect of Gd inclusion in the NbN superconductor thin films. The
films are deposited on single crystalline Silicon (100) by DC reactive
sputtering technique i.e., deposition of Nb and Gd in presence of reactive N2
gas. The fabricated relatively thick films (400 nm) are crystallized in cubic
structure. These films are characterized for their morphology, elemental
analysis and roughness by Scanning Electron Microscopy (SEM), Energy Dispersive
X-ray spectroscopy (EDAX) and Atomic Force Microscopy (AFM) respectively. The
optimized film (maximum Tc) is achieved with gas ratio of Ar:N2 (80:20) for
both pristine and Gd doped films. The optimized NbN film possesses Tc (R=0) in
zero and 140kOe fields are at 14.8K and 8.8K respectively. The Gd doped NbN
film showed Tc (R=0) in zero and 130kOe fields at 11.2K and 6.8 K respectively.
The upper critical field Hc2(0) of the studied superconducting films is
calculated from the magneto-transport [R(T)H] measurements using GL equations.
It is found that Gd doping deteriorated the superconducting performance of NbN.Comment: 14 pages Text+Figs: comments/suggestions
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