Barkhausen pulses

Switching Method. Sharp step functions or slow-rising sawtooth electrical pulses are applied to a ferroelectric specimen and the total switching current is measured as a function of time. For step-function inputs the resultant current pulse is a measure of the nucleation and growth of reversal domains, while for slow sawtooth inputs the current is usually a series of small pulses analogous to Barkhausen pulses in ferromagnetics. The results provide information regarding domain sizes and incremental volumes swept up by the jerky movement of domain walls. 

Eventually the domains lose their cylindrical shape and take up that shape governed by the variation of cr with lattice direction (i.e., become squared in BaTiOj, lenticular in TGS, etc.). As they grow in size they eventually touch and coalesce the rapid filling up of the reentrant regions near points of contact have been definitely associated with the larger Barkhausen pulses... 

Fig. 6.44. A typical Barkhausen signal plot, where the number of pulses is represented as a function of the applied field (schematic).

---