Behavior of higher harmonics of the granular HTSC response to a low-frequency magnetic field

A theoretical explanation is proposed for the experimental results on the b ehavior of higher harmonics of the granular HTSC response to a variable mag netic field of frequencies similar to 10(2) Hz. The theory explains the per iodicity in the dependence of the harmonics amplitudes on a static external magnetic field; the dependence of the period on the harmonics number and o n the amplitude of the variable magnetic field; the existence of the thresh old in the dependence of the odd-harmonics amplitudes on the amplitude of t he variable magnetic field; and the possible formation of pairs for these d ependences for the neighboring odd harmonics. It is shown that the experime ntal dependences can be explained without a detailed analysis of microproce sses in individual Josephson loops only by treating HTSC as a macroscopic m edium characterized by the dependence Phi(H) of the magnetic flux on the ex ternal magnetic field, which is typical of type II superconductors. (C) 200 0 MAIK "Nauka/Interperiodica".