  Results from dielectric and structural measurements on epitaxial
SrTiO$_3$/BaZrO$_3$ superlattices reveal properties that cannot be explained
simply in terms of those measured on single films of the constituent materials.
For large superlattice periodicities (20/20 and 38/38 structures, i.e. samples
in which each SrTiO3 and BaZrO3 layer are 20 or 38 unit cells thick,
respectively), the capacitance-voltage curves indicate room-temperature
ferroelectricity. For smaller periodicities (7/7 and 15/15),
anti-ferroelectric-type behavior is observed, suggesting strong coupling
between individual polar layers. This is consistent with recent second-harmonic
generation results [A.Q. Jiang et al., J. Appl. Phys. 93, 1180 (2003)] of
ordering in SrTiO$_3$/BaTiO$_3$ superlattices. However, both constituents of
the structures investigated here are paraelectric. Strain-induced
room-temperature ferroelectricity in SrTiO$_3$ and distance-dependent coupling
between these layers are proposed as mechanisms leading to the observed
behavior.
