  Superlattices built from two antiferromagnetic (AFM) charge/orbital order
compounds, $Pr_{0.5}Ca_{0.5}MnO_3$ and $La_{0.5}Ca_{0.5}MnO_3$, have been
studied as the thickness of $La_{0.5}Ca_{0.5}MnO_3$ ($LCMO$) varied. High
structural quality thin films were obtained on $LaAlO_3$ substrates using the
pulsed laser deposition technique. An antiferromagnetic-to-ferromagnetic
transition, in addition to an enhancement of the coercivity, are observed as
the $LCMO$ layer thickness increases. The small shift in the origin of the
field-cooled hysteresis loop along the field axis indicates the presence of
ferromagnetic and antiferromagnetic phases in the superlattices. We attribute
these features to the AFM spin fluctuations at the
$Pr_{0.5}Ca_{0.5}MnO_3/La_{0.5}Ca_{0.5}MnO_3$ interfaces resulting from the
strain effects.
