Harmonic susceptibilities of (Bi, Pb)2Sr2Ca2Cu3Oy bulk superconductors

Even harmonics of susceptibility have been measured as functions of de magnetic fields, the ac field amplitude and frequency for (Bi, Pb)(2)Sr2Ca2Cu3Oy bulk superconductors with magnetic fields parallel to the slab sample. The experimental results are compared with theoretical susceptibility curves based on the numerical calculation of the flux diffusion equation. The theoretical results are in good agreement with the temperature-, field- and frequency-dependent features of the experimental data. The frequency independent critical state model breaks down in explaining all these results even though its generalization can generate even harmonics of susceptibility. (C) 2001 Elsevier Science B.V. All rights reserved.