Chemical substitution induced ferroelectric polarization rotation in BiFeO$_{3}$ thin films

The direction of the polarization vector in ferroelectric materials is an important parameter critical to a number of applications. Polarization orientation in ferroelectric thin films can be controlled by various approaches such as electric- field induced rotation and strain engineering using exotic substrates. We have performed systematic chemical substitution of rare earth cationic dopants, in particular Sm in the BiFeO$_ {3}$thin films, and found that the polarization vector rotates from the (111) to the (001) direction as a continuous function of the dopant concentration. This is accompanied by enhanced dielectric $\epsilon$$_{33}$ as well as piezoelectric coefficient d$_{33}$, and the maximum in d$_{33}$ (110 pm/V) is achieved at 14\% Sm. We will discuss the correlation between the polarization rotation, structural evolution and other properties as a function of chemical substitution.