Investigation of plastic deformation in a mixed state superconductor

The work has been aimed at an experimental study of the interaction between moving dislocations and the Abrikosov vortices in the mixed state of a superconductor. To that end the abrupt change of the deforming stress was studied that occurred during the transition of the specimen from the superconducting to the mixed state and vice versa, in samples deformed in tension at a rate of 7 x 10-4 s-1. The transition was provoked by application of external fields of different orientation with respect to the tensile axis. Objects of the investigation were Pb-In alloys of various concentrations. In the mixed state the magnitude of the abrupt stress changes shows considerable variations which have been attributed to the dislocation drag by the vortices. The measured value normally is several tenths of 1 N/mm2. The experimental results are compared with calculated predictions for the vortex drag force due to lattice defects. (author)