8.2.2 Simulation of Materials with Biaxial Anisotropy

Simulation of biaxial anisotropy shows different properties and, since the model is more complex, additional effects. The simulations concentrate on a material, with two perpendicular anisotropy axes.

Again first investigations are focused on the hysteresis of the $Q/V$ characteristics. The down branches are plotted in Fig. 8.10. It is easy to see that if the electric field is parallel to one of the anisotropy axes, the same results as for uniaxial materials are obtained. Similarly to the uniaxial case, an increase of the angle between the anisotropy axis and the device axis leads to a reduction of polarization, but only until the angle reaches $45^\circ$.

The most interesting effect visible in Fig. 8.10 is the occurrence of kinks in the Q/V characteristic. These kinks develop when the axial components are reduced because their sum exceeds the saturation polarization.

The different polarization components and the total polarization are plotted separately, as shown in Fig. 8.11, Fig. 8.12, and Fig. 8.13. The angles of the anisotropy axes to the axes of the device were $15^\circ$ and $75^\circ$, respectively. The applied potential was 0.91 V.

Figure 8.10: Hysteresis curves for different angles of the anisotropy axes; two perpendicular anisotropy axes are applied

Figure 8.11: Total polarization in a device with two anisotropy axes

Figure 8.12: Polarization in the first anisotropy direction, angle = $15^\circ$

Figure 8.13: Polarization in the second anisotropy direction, angle = $75^\circ$