Three different methods for the analysis of magnetic-relaxation data, M(t, T), are presented: In one model a spectrum, p (U), of activation energies U is considered, whereas the other model is based on the existence of a single barrier, permitting arbitrary dependences U(j~M), where j denotes the current density. These two models are applied to experimental relaxation data, carried out on Bi2Sr2CaCu2Os+,~ single crystals. The results are not in contradiction with each other but probe different aspects of the creep process. In consequence the time decay of the magnetization, M(t, T), can be interpreted either by the existence of a spectrum p (U) of activation energies or as being due to a single activation energy, U(M(t) ), that increases with time.
In a third, unique model, the combination of a spectrum p(U) assuming a linear relation U~j is considered.
From theoretical investigations of demagnetization effects the conclusion is drawn, that magnetic relaxation of samples with extreme geometries, i.e. thin films, has to be considered carefully, because there are stray-field effects contributing to the relaxation function, that do not necessarily follow the same time law.