Local magnetic relaxation experiments are carried out on YBa2Cu3O7-delta th
in films by magneto-optics. The current density is calculated quantitativel
y by an inversion scheme of Blot Savart's law which gives direct informatio
n about the time evolution of the current density with a high spatial resol
ution of about 5 mum. We determine the local activation energies U-0(x,y) b
y fitting different relaxation laws at different positions (x, y) in the fi
lm plane. This analysis yields a spectral distribution of the activation en
ergies that is independent of the applied model. Possible mechanisms which
could lead to such a distribution are discussed.