Drift of scanning cycles of microwave absorption in high-T c superconductors

A change in the position and shape of the hysteresis line of magnetically modulated microwave absorption accompanying repeated magnetization reversal of a high-T _c superconductor was observed. The shift of the signal increases with the magnetic field, and its modulation amplitudes and scanning times vanish at T _c, obeying the basic laws of the temperature dependence of the line in single crystals and ceramics. Its appearance is correlated with the attainment of the critical state of modulated screening currents of weak-link loops separated on the surface of the sample and can be interpreted as their interaction on the basis of a generalized surface barrier model. The observed anisotropy indicates a Néel interaction mechanism. Fiz. Tverd. Tela (St. Petersburg) 41, 567–571 (April 1999)