Investigations of the superconducting transition in polycrystalline yttrium barium copper oxide

• Main Author: Joshi, Rasheed Jimmy
• Language: ENG
• Published: ScholarWorks@UMass Amherst 1996
• Subjects: Condensation
• Online Access: https://scholarworks.umass.edu/dissertations/AAI9638980

We present results of measurements designed to study superconducting I-V scaling in samples of bulk $\rm YBa\sb2Cu\sb3O\sb{7-\delta}$ with varying morphologies, 1$\mu$m $\rm\leq\langle d\sb{g}\rangle\leq20\mu m$ and at selected magnetic fields, $0.5{\rm G}\leq H\leq10\ {\rm T}.$ I-V isotherm measurements performed near the superconducting transition on the samples are consistent with recent predictions of I-V scaling, with critical exponents $\nu\sim1.1-1.75$ and $\rm z\sim2.3-4.3.$ The values for $\nu$ are comparable to those previously reported. The values for z are consistent with those reported by Tieman and Hallock but are somewhat lower than what is predicted by the glassy models. The static exponent does not seem to display any morphology or magnetic field dependence. The dynamic exponent, however, does display some morphology dependance with z higher for the small grain size samples. Furthermore, the data shows some evidence for a crossover between low and high z values in increasing magnetic fields.