Peak effect in a superconducting DyBa 2 Cu 3 O 7 − δ film at microwave frequencies

We report the observation of a peak in the microwave (9.55 GHz) surface resistance in an epitaxial DyBa2Cu3O7–δ superconducting film in magnetic fields (parallel to the c axis) ranging between 0.2 to 0.9 T. Such a peak is absent in the measurements done in zero field. The temperature and field dependence of the peak suggests that this peak could be associated with the peak effect (PE) phenomenon reflecting the order-disorder transformation in the flux-line lattice (FLL). A strong frequency dependence of the PE is observed close to the depinning frequency of the FLL.