Exchange coupling induced antiferromagnetic-ferromagnetic transition in Pr$_{0.5}$Ca$_{0.5}$MnO$_3$/La$_{0.5}$Ca$_{0.5}$MnO$_3$ superlattices.

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.