Physical Processes Near and on a Twin Boundary in High-Temperature Superconductors and an Oscillatory Differential Method for Investigating These Processes

An oscillatory differential method is developed for local diagnostics of superconductors with a view to obtaining useful information simultaneously on the physical processes that occur near and on a twin boundary and on the period of twin boundaries. In the magnetic-field dependence of the trapped magnetic flux and of the effective demagnetization factor of YBCO samples in the form of a thin disk, regular steps are observed over certain intervals of the external field. These results are attributed to the decomposition of a sample into twin domains as the external magnetic field increases and allow one to determine the transversal size of the domains.