Generalized inversion scheme for the determination of activation energies from flux-creep experiments in high-Tcsuperconductors

For thermally activated flux creep, which can be characterized by a temperature-magnetic-field-, and current-density-dependent activation energy U(j,T;${\mathit{B}}_{\mathit{e}}$), we show that this function can be determined from a combination of magnetization and magnetization dynamical relaxation rate data. As an illustration the method is applied to creep data on epitaxial ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ thin films. In contrast to previously proposed procedures, the present inversion scheme is much more general as it does not require a priori assumptions about the explicit temperature or field dependence of U.