Excess conductivity analysis of heavy ions irradiated TlBa2(Ca2−Mg )Cu3O10− superconductor (original) (raw)
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Excess conductivity analysis of heavy ions irradiated TlBa2(Ca2−yMgy)Cu3O10−δ superconductor
Physica B: Condensed Matter, 2015
The excess conductivity analysis of resistivity versus temperature data of TlBa 2 (Ca 2 À y Mg y )Cu 3 O 10 À δ (y¼ 0.5, 1.0, 1.5) superconductor samples have been performed in the light of Aslamasov-Larkin and Lawrence-Doniach theories before and after irradiation with a beam of gold (Au 4 þ ) ions of energy 20 MeV having a fluence of 1 Â 10 15 ions/cm 2 . The microscopic parameters such as zero temperature coherence length {ξ c (0)}, inter-plane coupling constant (α), and Fermi velocity (V F ) have been calculated from the ln-ln plot of excess conductivity (Δσ) versus reduced temperature (ε) using the Lawrence and Doniach model. The cross-over temperatures separating different fluctuation regions in the ln-ln plot are also determined. It is observed from the excess conductivity analysis that all the microscopic parameters have been decreased after the irradiations. Whereas, calculations have shown that critical magnetic fields (B c ) and critical current density (J c ) are increased after the ion irradiation, which, confirms the validity of the results because B c and J c are increased by the formation of artificial pinning centers after bombardment of energetic heavy ion beam.
Magneto-resistance and Excess Conductivity Studies of Tl(Ba2−y Mg y )Ca 2 Cu 3 O 10−δ Samples
Journal of Superconductivity and Novel Magnetism, 2014
The excess conductivity analysis of resistivity versus temperature data of TlBa 2 (Ca 2 À y Mg y )Cu 3 O 10 À δ (y¼ 0.5, 1.0, 1.5) superconductor samples have been performed in the light of Aslamasov-Larkin and Lawrence-Doniach theories before and after irradiation with a beam of gold (Au 4 þ ) ions of energy 20 MeV having a fluence of 1 Â 10 15 ions/cm 2 . The microscopic parameters such as zero temperature coherence length {ξ c (0)}, inter-plane coupling constant (α), and Fermi velocity (V F ) have been calculated from the ln-ln plot of excess conductivity (Δσ) versus reduced temperature (ε) using the Lawrence and Doniach model. The cross-over temperatures separating different fluctuation regions in the ln-ln plot are also determined. It is observed from the excess conductivity analysis that all the microscopic parameters have been decreased after the irradiations. Whereas, calculations have shown that critical magnetic fields (B c ) and critical current density (J c ) are increased after the ion irradiation, which, confirms the validity of the results because B c and J c are increased by the formation of artificial pinning centers after bombardment of energetic heavy ion beam.
Physica C-superconductivity and Its Applications, 2011
The Cu 1Àx Tl x Ba 2 Ca 1 Cu 2 O 8Àd superconductor thin film samples were bombarded with protons, Si and Au ions of energies 6, 20 and 20 MeV respectively using 5MV tandem pelletron accelerator at Experimental Physics Labs. Each un-irradiated sample had different values of normal state resistivity and the zero resistance critical temperature. The zero resistivity critical temperature has been increased after the irradiation by Si and Au ions. The fluctuation induced conductivity (FIC) analysis of the as-prepared and the ion irradiated samples were performed in the light of Aslamasov-Larkin (AL) theory. The FIC analysis has shown three dimensional (3D) fluctuations in the order parameter in all the samples along with a cross-over to two dimensional (2D) fluctuations at higher temperature. The 3D-2D cross-over temperature has been shifted to higher values after the ion irradiation. Moreover, a direct correlation between the zero resistivity critical temperature, 2D-3D cross-over temperature (T LD ) and superconductivity fluctuation temperature (T scf ) was observed. These studies have shown that the fluctuation induced conductivity (excess conductivity) depends on the density of defects and is independent of their nature.
Physica C-superconductivity and Its Applications, 2011
The Cu 1-xTl xBa 2Ca 1Cu 2O 8-δ superconductor thin film samples were bombarded with protons, Si and Au ions of energies 6, 20 and 20 MeV respectively using 5MV tandem pelletron accelerator at Experimental Physics Labs. Each un-irradiated sample had different values of normal state resistivity and the zero resistance critical temperature. The zero resistivity critical temperature has been increased after the irradiation by Si and Au ions. The fluctuation induced conductivity (FIC) analysis of the as-prepared and the ion irradiated samples were performed in the light of Aslamasov-Larkin (AL) theory. The FIC analysis has shown three dimensional (3D) fluctuations in the order parameter in all the samples along with a cross-over to two dimensional (2D) fluctuations at higher temperature. The 3D-2D cross-over temperature has been shifted to higher values after the ion irradiation. Moreover, a direct correlation between the zero resistivity critical temperature, 2D-3D cross-over temperature ( TLD) and superconductivity fluctuation temperature ( Tscf) was observed. These studies have shown that the fluctuation induced conductivity (excess conductivity) depends on the density of defects and is independent of their nature.
Effect of Ag15+ and Li3+ ion irradiation on superconducting Tl2Ca2Ba2Cu3O10 single crystals
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2011
The effect of irradiation by 50 MeV Li 3+ and 200 MeV Ag 15+ ions on single crystals of Tl 2 Ca 2 Ba 2 Cu 3 O 10 (Tl2223) superconductor has been investigated at different fluences. Isothermal magnetization hysteresis loops have been recorded at different temperatures using a SQUID magnetometer and the effect of irradiation on the critical current density, irreversible field, second magnetization peak and pinning force has been studied. Irradiation by 200 MeV Ag 15+ ions resulted in increased hysteresis and irreversibility field while no change in second magnetization peak position and critical temperature was observed. A broadening in the hysteresis loop before the second magnetization peak was also observed for the crystals irradiated by Li 3+ ions. Annealing of irradiated crystals at 500°C resulted in reduction of point defects created by Li 3+ ions.
Synthesis and excess conductivity analysis of TlBa 2 (Ca 32y Be y )Cu 4 O 122d superconductors
TlBa 2 (Ca 3-y Be y)Cu 4 O 12-d (y = 0, 0.5, 1.0, 1.5, 2) samples are synthesized at normal pressure and the influence of doped Be-atoms on the superconductivity parameters at the microscopic level is investigated by carrying out excess conductivity analyses of conductivity data. The samples have shown tetragonal structure and the unit cell volume decreases with increased Be-doping. The onset temperature of superconductivity [T c (onset)] and zero resistivity critical temperature [T c (R = 0)] decrease with increased Be, however, the magnitude of diamagnetism is enhanced with Be (except for Be-doping of y = 1.0). The apical oxygen mode of the type Tl–O A –Cu(2) and CuO 2 planar oxygen mode are softened as observed in FTIR absorption measurements. The FIC analyses of conductivity data have shown an increase in the coherence length along the c-axis and inter-plane coupling. The values of B c0 (T), B c1 (T), J c (0), s u are improved with the doping of Be. These observations suggested that due to the proximity effect there is less suppression in the value of the order parameter of the Cooper pairs from |w| 2 = 1 value in the CuO 2 planes in Be-doped samples that maintains the density of carriers in the conducting CuO 2 planes [since the |w| 2 = n/2] which promotes enhancement in the magnitude of superconductivity.
Doping of the CuO2 planes of Cu1−xTlxBa2Ca2Cu3O10−y superconductor via light and heavier ions
Physica C: Superconductivity, 2003
The superconducting properties of Cu 1Àx Tl x Ba 2 Ca 2 Cu 3 O 10Ày thin films prepared by amorphous phase epitaxial (APE) method have been studied, by resistivity measurements, X-ray diffraction, electron microscopy and infrared spectroscopy. The main emphasis of this research work is on the doping of the charge reservoir layer, which ultimately controls carrier concentration in the CuO 2 conducting planes. The phenomena of the superconductivity, takes place in the conducting CuO 2 planes, however, we can control it via charge concentration in the CuO 2 planes. We have done this by carrying out annealing experiments in different conditions i.e. in air, nitrogen atmosphere and in vacuum. In these annealing experiments the doping is carried out by intercalation of the light O 2 in the CuO chains and by the removal of heavy thallium from the CuO chain axis. The removal of thallium at 717°C from the CuO chains shifted the T c (R ¼ 0) to higher values and the doping of oxygen and nitrogen at 450°C increased the semiconductivity and shifted the T c (onset) to lower values. The removal of oxygen from CuO chains by vacuum annealing at 450°C has also increased the degree of semiconductivity and shifted the T c (onset) to lower temperatures. The XRD of the samples of Cu 1Àx Tl x -1223 phase showed the predominant c-axis oriented material with c-axis lattice constant 15.53 A A. The electron micrograph of these samples showed elongated grains with the grains ends fused together. The surface roughness of the samples was below 0.2 lm. The infrared absorption measurements have shown the softening of 451 cm À1 mode after removal of oxygen from the unit cell, which shows that oxygen doping controls the carrier concentration in the charge reservoir layer and hence the superconductivity in the material.
Journal of Applied Physics, 2012
The effect of oxygen annealing on the excess conductivity of Cu 0.5 Tl 0.25 M 0.25 Ba 2 Ca 2 Cu 3 O 10Àd (M ¼ K, Na, Li, Tl) samples is investigated. From the analysis of results, we have evaluated the exponents, the coherence length, the crossover temperature, and interlayer coupling strength (J) of the samples. These studies show that the K-doped post-annealed sample has shown narrow transition width with improvement in 2D and 3D conductivities. Oxygen annealing has also enhanced the coherence length and interlayer coupling strength of the material. Na-and Li-doped postannealed samples have shown increased transition width, poor 2D and 3D conductivities within narrow temperature windows. After annealing, reduction in coherence length and the interlayer coupling strength is also observed. While in Tl-doped sample, oxygen annealing has not caused much deviation in fluctuation induced conductivity (FIC) parameters. The underlying cause of improved behavior of post-annealed K-doped sample is also discussed.
Effect of γ-irradiation on polycrystalline Tl1Ba2Ca2Cu3Oy superconductor
Physica B: Condensed Matter, 2002
Specimens of polycrystalline Tl 1 Ba 2 Ca 2 Cu 3 O y superconductor (Tl-1223) have been irradiated at room temperature by g-rays. The variations of the normal state resistance, transition width and the critical current densities with girradiation up to about 400 MR were studied. The normal state resistivity rðTÞ increases gradually up to a dose of 100 MR, whereas at higher doses, the effect of irradiation becomes rather negligible. The transition temperature T c decreases slightly and the transition temperature width DT broadens at doses below 100 MR with almost no change at higher doses up to 400 MR. At relatively low temperatures and low g-doses, the critical current densities J c ðTÞ increase with g-irradiation, while the effect of g-irradiation at temperatures very close to T c is rather negligible. Obtained results confirmed the high sensitivity of (Tl-1223) superconductor to g-irradiation at relatively low g-doses. These results are discussed and explained in terms of the effect of g-rays on the weak links and Josephson junctions between the grains. r
Excess conductivity of Cu0.5Tl0.5Ba2Ca3Cu4−yZnyO12−δ superconductors
Low Temperature Physics, 2012
Oxide high-T c superconductors (HTSC) are anisotropic in character since the charge carriers have free moment in the conducting CuO 2 planes [1] whereas their motion is impeded by insulating/partially insulating MBa 2 O 4-δ (M = Y, Bi, Hg, Tl, CuTl, etc.) charge reservoir layers. In the transport process the charge carriers have to tunnel across insulating/partially insulating barriers along the c-axis and across the grain boundaries, which promote a fluctuation in the order parameter and in turn to the conductivity of the carriers. The studies of such fluctuation conductivity (FIC) may help in understanding the intrinsic mechanism of superconductivity. Here the electrical resistivity ρ(T) versus temperature data of as-prepared and oxygen post-annealed Cu 0.5 Tl 0.5 Ba 2 Ca 3 Cu 4-y Zn y O 12-δ (y = 0, 0.5, 1.5, 2.5) samples is studied for FIC analyses in the temperature regime well above the critical temperature; such analyses have been carried out by employing Lawrence and Doniach (LD) and Maki-Thompson (MT) models. The coherence length, inter-plane coupling, exponent, dimensionality of fluctuations and the phase relaxation time of the carriers are determined from such analyses. It is observed that the crossover temperature associated with two distinct exponents fits very well with the two-dimensional (2D) and three-dimensional (3D) LD equations. The crossover temperature T 0 is shifted to higher temperatures with enhanced Zn doping. The 3D LD region is shifted to higher temperature with the increased Zn doping. We have elucidated from these analyses that lower Tl content in the final compound may increase the charge carrier's doping efficiency of MBa 2 O 4-δ charge reservoir layer, resulting into an increase in the coherence length along the c-axis and superconductivity parameters. A small decrease in the coherence length along the c-axis ξ c (0) is observed in the samples with Zn doping of y = 1.5 whereas ξ c (0) increases in the samples y = 0.5, 2.5. In comparison with as-prepared samples, the ξ c (0) decreases after post-annealing in oxygen atmosphere. It is most likely that a decrease in the density of charge carrier's is promoted by oxygen diffusion in the unit cell may suppress the ξ c (0). The increase oxygen diffusion is evidenced from the softening of phonon modes after postannealing in oxygen atmosphere. The decreased population of small spins of Cu atoms induced by doping of Zn is viewed in the terms of suppression of spin gap and hence the pseudo-gap in Cu 0.5 Tl 0.5 Ba 2 Ca 3 Cu 4-y Zn y O 12-δ (y = 0, 0.5, 1.5, 2.5) samples.