Harmonic response of textured YBa2Cu3O7 superconductor

Harmonic AC susceptibilities as a function of temperature (T), AC field frequency (f), amplitude (B-ac) in DC field (B-dc) have been studied numerically as well as experimentally. The numerical calculation is based on nonlinear Vortex diffusion. The numerical result shows that there exists a second harmonic, although very weak, while a third harmonic is strong. The location of the third harmonic shifts toward low temperature while its height increases with either decreasing f or increasing B-ac. These numerical results are in agreement with experimental results observed for textured YBa2Cu3O7 and in contrast with prediction of the Bean critical state model or self-organized criticality. It is also shown that the height of the third harmonic peak depends on B-ac and f more sensitively than that of the fundamental one. (C) 1999 Elsevier Science Ltd. All rights reserved.