Physica C: Superconductivity 417, 141 (2005)
K. Schindler, M. Ziese, P. Esquinazi, H. Hochmuth, M. Lorenz, K. Zimmer and E.H. Brandt
Abstract
The critical current density and flux-creep activation energy of YBa2C3O7 rings were determined from ac-susceptibility measurements. A novel approach was developed theoretically and experimentally to derive the flux-creep exponent from higher susceptibility harmonics. An alternative method using a scaling approach yielded similar sample-to-sample variations, but qualitatively different values for the flux-creep exponent. This is discussed considering the limits of validity of the logarithmic approximation to the flux-line activation energy.
