The fundamental and high-order harmonic susceptibility, chi(n) = chi(n)' + i chi(n)'' (n = 1, 3, 5 and 7) were measured as a function of temperature (50-130 K), frequencies (11 and 140 Hz) and AC magnetic field amplitude (80-1280 A/m) on a bulk Tl2Ba2Ca2Cu3O10 high-T-c superconductor prepared by the solid-state reaction method. They exhibit dependence on the amplitude of the AC field. The observed dependences were analyzed by using the Bean Model. We have obtained an empirical function for the penetration field H-p = H-alpha(1-t)(beta), with t = T/T-cb. Best fitting to data was obtained with parameters H-alpha approximate to 2.6 x 10(4) A/m and beta = 1.74. The experimental values agree well with the theoretical findings. The XRD pattern, resistivity measurement and SEM analysis were also carried out to characterize the sample. (c) 2005 Elsevier B.V. All rights reserved.