Resistive dissipation in imperfect crystals of YBa2Cu3O7−δ

Abstract

We have measured ac magnetoresistance in fields up to 8 T in a variety of YBa₂Cu₃O_7−δ single crystals containing (a) twin boundaries only in one direction, (b) multi‐twin domain structure, and (c) growth steps. We find two components of the resistance: an angular dependent Lorentz force induced ‘‘excess resistivity’’ superimposed on an angular independent resistivity. The temperature and magnetic field dependence of the angular‐dependent resistivity exhibit a strong correlation with crystal defects, whereas the angular‐independent resistivity remains virtually unchanged. In addition, we find crystals exhibiting both ohmic and non‐ohmic behavior in their I‐V characteristics depending on crystal imperfections.