Oxygen dynamics in epitaxial YBa2Cu3O7-delta thin films

We have investigated epitaxial YBCO films by Perturbed gamma gamma-Angular Correlation Spectroscopy (PAC) using In-111 probe atoms. The probes substit ute on the yttrium lattice site and hyperfine parameters have been determin ed unambiguously. Excellent agreement is achieved with full potential elect ric field gradient (efg) calculations. Good reproducibility has been achiev ed by our preparation method allowing us to study the influence of oxygen m otion on the structural orthorhombic to tetragonal phase transition.