Temperature and field dependence of thermally activated flux flow resistance in Bi2Sr2CaCu2O8+δ superconductor

Abstract

We study the temperature dependence of the resistivity as a function of magnetic field in superconducting transition (T c onset -T c R=0 ) region for different Bi 2 Sr 2 CaCu 2 O 8+δ superconducting samples being synthesized using sol-gel method. The superconducting transition temperature (T c R=0 ) of the studied samples is increased from 32 K to 82K by simply increasing the final sintering temperature with an improved grains morphology. On the other hand, broadening of transition is increased substantially with decrease in sintering temperature; this is because T c onset is not affected much with grains morphology. Further broadening of the superconducting transition is seen under magnetic field, which is being explained on the basis of thermally activated flux flow (TAFF) below superconducting transition temperature (T c ). TAFF activation energy (U 0 ) is calculated using the resistive broadening of samples in the presence of magnetic field. Temperature dependence of TAFF activation energy revealed linear temperature dependence for all the samples. Further, magnetic field dependence is found to obey power law for all the samples and the negative exponent is increased with increase in sintering temperature or the improved grains morphology for different Bi-2212 samples. We believe that the sintering temperature and the ensuing role of grain morphology is yet a key issue to be addressed in case of cuprate superconductors.

Effect Y substitution on the microstructure, transport and magnetic proprieties of Bi2Sr2Ca1Cu2O8+δ superconducting ceramics

“…4. Nearly the same values of U 0 were also obtained by Sharma et al [45] in the measurements up to 14 T on Bi-2212 polycrystalline samples, prepared by sol-gel method and annealed between 760°C and 840°C, where they showed an influence of annealing temperature on U 0 . With lead containing (Bi,Pb)2212 samples doped by a rare earth on Sr site the obtained values are much higher, 0.075 eV to 0.308 eV with an applied field of 0.28 T for Gd doping [40] and 0.077 eV to 0.47 eV with an applied field of 0.32 T and 0.63 T for Tb doping [41].…”

“…The pinning properties, expressed in the irreversibility line, have been at this time studied in Y substituted Bi-2212 crystals [33]. To our knowledge, no study has been made before about the effect of Y doping on the activation energy of Bi-2212 ceramic samples as it has been made for undoped Bi-2212 crystal [2], and in more recent works on doped and undoped Bi based polycrystalline samples [41][42][43][44][45]. This effect is presented for the case of Y substitution on the Ca site at the rate varying up to 25 % (x = 0.25), under applied magnetic field having a constant amplitude equal to 0 T, 1 T, 2 T and 3 T.…”

Enhanced superconducting performance of melt quenched Bi2Sr2CaCu2O8 (Bi-2212) superconductor

“…The flow of vortices in this region is caused by thermal activation and hence, is known as thermally activated flux flow (TAFF) [12]. Thus, resistivity in this region is given by well known Arrhenius equation, ρ = ρ 0 (B,T)e -U 0 /κ B T [31] [32], where U 0 is the TAFF activation energy, which can be obtained from the slope of the linear part of the ln (ρ/ρ 0 ) versus T -1 plot.…”

Effect of Ce Substitution on the Magnetoresistivity and Flux Pinning Energy of the Bi2Sr2Ca1−x Ce x Cu2O8+δ Superconductors

“…After the first prediction of flux creep by Anderson [19], many studies have been directed towards the effect of an applied external magnetic field on the resistive transition in order to understand the mechanism of flux pinning and flux motion [20][21][22][23][24][25][26][27]. There are several models for understanding the resistivity broadening under a magnetic field, such as thermally activated flux creep [22], flux flow [21], flux line melting and flux cutting [28].…”