Paraconductivity in YBa2Cu3O7 and YBa2Cu3O7 thin film composites with cerium oxide and gold

Structural examinations and resistivity measurements were made on Bi1.75Pb0.35Sr2Ca2Cu3O10 samples sintered at different temperatures. The excess conductivity region was analysed using the Aslamazov–Larkin (AL) expression. In agreement with the theoretical predictions, the ln(Δσ/σ300)–ln(ε) plots exhibited three different regions, namely, critical, mean field and short wave fluctuation regions. In the mean field region, the interlayer coupling strength ν, the effective layer thickness d, and the zero-temperature coherence length ζ(0) were estimated using the Lawrence–Doniach (LD) expression.

Section: Resultscontrasting

confidence: 89%

Influence of sintering temperature on excess conductivity in Bi-2223 superconductors

Ibrahim

Saleh

2007

“…Unambiguous determination of T c , however, is difficult in cuprate superconductors due to the presence of fluctuation effects, which round the critical behavior of any observable near T c [10,11]. We have used the derivative of the resistance data as a function of temperature ( dR dT ), with T c defined as the peak position of this derivative, as has been done by many others [10,12,13]. The zero resistance temperature, T c0 , is defined as the temperature at which the resistance measured with decreasing temperature goes below the resolution.…”

Section: Methodsmentioning

confidence: 99%

Point defect creation by low fluence swift heavy ion irradiation-induced low energy electrons in YBa₂Cu₃O_7−y

Biswal

John

Behera

et al. 2008

The effect of 200 MeV Ag ion irradiation on the superconducting and normal state properties of the high-Tc superconductor YBa2Cu3O7−y (YBCO) is studied by in situ temperature-dependent resistance measurements. We show that irradiating YBCO thin films (∼150 nm) at low temperature result in a softly defected region of about 85 nm radius due to swift heavy ion-induced secondary electrons around the highly amorphized latent tracks of ∼5 nm radius. This leads to a decrease of Tc at fluences three orders of magnitude less than the threshold fluence, where overlapping of tracks block the supercurrent path. Due to their low energy (4.1 keV for 200 MeV Ag ions), the secondary electrons can induce point defects by inelastic processes rather than by direct elastic collision.

“…Both the methods however do not rule out error in T c determination since the exponent in the SCOPF region varies over a large range. We have used the derivative of the resistivity data as a function of temperature ( dρ dT ), with T c defined as the peak position of this derivative (figure 1) as has been done by many [8,9,14]. The effect of uncertainty in the determination of the T c results in a temperature range corresponding to the critical region, where the excess conductivity sensitively depends on the reduced temperature [15,16].…”

Section: Methods Of Data Analysismentioning

confidence: 99%

“…On the other hand, the critical region just above T c has a strong dependence on the microstructure of the YBCO samples [8,9], which in turn depends on the Ag content in the films. Lobb [20] has theoretically analysed the critical fluctuations and defined the critical region as…”

Section: Mesoscopic Inhomogeneitymentioning

confidence: 99%

See 1 more Smart Citation

Fluctuation conductivity and inhomogeneity in granular YBa₂Cu₃O_7−y/Ag composite thick films

Mohapatra¹,

Biswal²,

Behera³

et al. 2006

We analyse the effect of interplay of the different types of inhomogeneities and the thermal fluctuation of the superconducting order parameter on the excess conductivity in a set of YBa2Cu3O7−y/Ag composite thick films. We show that the mesoscopic inhomogeneities arising due to most of the Ag residing at the grain boundaries strongly influence the tailing and the critical regions below and above the mean field transition temperature, Tc, respectively. A small fraction of Ag diffusing into the grains also produces microscopic inhomogeneities. Though these inhomogeneities are not expected to influence the SCOPF, we found that TLD, corresponding to the transition from the two to three dimensional fluctuation of the order parameter in the mean field region, as well as the inter-planar coupling strength, strongly depend on the Ag content in the composites. The effect of Ag induced inhomogeneities on the temperature window corresponding to different phases in the mean field and the critical regions are depicted in the form of a phase diagram. The large variation of TLD, and near invariance of Tc with Ag content in the films as seen in the phase diagram, are explained by invoking the role of Ag in modifying the overall electronic structure of the grains.