We present measurements of harmonic generation in the magnetization of sintered pellets of YBa₂Cu₃O₇ and Bi_1.7Pb_0.3Sr₂Ca₂Cu₃O₁₀ as a function of DC field. The DC field is applied in the field-cooled mode. Measurements are made at 77 K for various values of the AC field amplitude. A comparison is made with calculations done within the critical state model.

Results are presented for study of nonlinear magnetization of a sintered YBa₂Cu₃O_7−y pellet of different thickness of a sample subjected to very low magnetic field. On cooling the sample belowT_c in zero field a change, in the oscillatory structure of harmonics in increasing dc field is observed in very low ac magnetic field. The effect of finiteness of the sample on the oscillatory structure and on the hysteresis of harmonics is also studied. The results are explained qualitatively.