Nano-magnetism at interfaces in high-temperature superconductors?

J. Mannhart, T. Kopp, C. Laschinger, C.W. Schneider and A. Weber
Experimentalphysik VI, EKM, Institute of Physics, University of Augsburg, D-86135 Augsburg, Germany

Interfaces can profoundly modify correlation effects in materials with correlated electron systems. New phases may appear at interfaces, the balance between phases that compete in the bulk may be shifted. To analyze the mechanism that causes grain boundaries in high-Tc superconductors to be weak links - the major problem for the fabrication of superconducting cables - we have measured the transport properties of these interfaces in novel and optimized ways. These measurements provide surprising results, which we can understand only if we consider the presence of nano-scale magnetism at these interfaces.