  A key property that drives research in ferroelectric perovskite oxides is
their strong piezoelectric response in which an electric field is induced by an
applied strain, and vice-versa for the converse piezoelectric effect. We have
achieved an experimental enhancement of the piezoelectric response and
dielectric tunability in artificially layered epitaxial PbTiO$_{3}$/CaTiO$_{3}$
superlattices through an engineered rotation of the polarization direction. As
the relative layer thicknesses within the superlattice were changed from sample
to sample we found evidence for polarization rotation in multiple x-ray
diffraction measurements. Associated changes in functional properties were seen
in electrical measurements and piezoforce microscopy. The results demonstrate a
new approach to inducing polarization rotation under ambient conditions in an
artificially layered thin film.
