3.2.2 Depolarization

Preisach hysteresis allows the simulation of the well-known effect of depolarization: If the response of a triangularly shaped signal with constantly decreasing amplitude as it is applied for depolarization of ferroelectric materials is calculated, the scheme outlined above has to be followed. It is assumed that the electric field is reduced to an operating point $E_B$ and then increased again to the next operating point $E_C$. The according Preisach-Everett diagram is plotted in Fig. 3.9.

Figure 3.9: Preisach-Everett diagram after two turning points

It is obvious that the dipoles that are already in the up direction (light red color) do not have to change their state. If the row of turning points with decreasing amplitude is extended, a distribution with the size of the up and down areas fairly equivalent, as outlined in Fig. 3.10, will evolve.

Figure 3.10: Preisach-Everett diagram, depolarization

Figure 3.11: Hysteresis loop for depolarization

Consequently, the resulting polarization will be almost zero at zero applied field, thus reproducing a well-known physical fact. The hysteresis curve which documents the depolarization process is plotted in Fig. 3.11.