A novel method for the determination of the flux-creep exponent from higher harmonic ac-susceptibility measurements

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.