Collective-pinning theory and the observed vortex dynamics in RBa2Cu3O7-δ crystals

We establish a framework for the analysis of magnetization data on high-temperature superconductor crystals that allows direct comparison with vortex-pinning theory. When the magnetization loops exhibit scaling behavior, as they do over a large part of the B-T plane for RBa2Cu3O7-δ crystals, the effective pinning energy Ueff has to contain power-law field dependences for the characteristic energy and current scales U0 and J0; these power-law exponents can be obtained directly from the data. Many regimes of collective-pinning (CP) theory do predict such power laws, but none yield exponents in agreement with those that are measured. The discrepancy appears to arise because U0 is observed to decrease with B, in contrast to the CP predictions. copyright 1996 The American Physical Society