  The hysteretic and reversible polarity-dependent resistive switch driven by
electric pulses is studied in both Ag/Pr0.7Ca0.3MnO3/YBa2Cu3O7 sandwiches and
single-layer Pr0.7Ca0.3MnO3 strips. The data demonstrate that the switch takes
place at the Ag-Pr0.7Ca0.3MnO3 interface. A model, which describes the data
well, is proposed. We further suggest that electrochemical diffusion is the
cause for the switch.
