La${}_{0.7}$Ca${}_{0.3}$MnO${}_3$ optimally doped epitaxial films were grown on ferroelectric BaTiO${}_3$ substrates. Electronic transport (magnetoresistance and electroresistance) and magnetic properties showed important anomalies in the temperature interval between 60 and 150 K, below the metal-insulator transition. Scanning probe microscopy revealed changes in BaTiO${}_3$ surface morphology at those temperatures. La${}_{0.7}$Ca${}_{0.3}$MnO${}_3$ thickness is a critical factor: 120-Å-thick films showed large anomalies sensitive to electric poling of the BaTiO${}_3$, whereas the behavior of 150-Å-thick films is closer to that of the reference La${}_{0.7}$Ca${}_{0.3}$MnO${}_3$ samples grown on SrTiO${}_3$. We propose that, through inhomogenous strain and electric polarization effects, the ferroelectric substrate induces an inhomogenous spin distribution in the magnetic layer. This would imply the coexistence of in-plane and out-of-plane ferromagnetic patches in La${}_{0.7}$Ca${}_{0.3}$MnO${}_3$, possibly interspersed with antiferromagnetic regions, as it has recently been theoretically predicted. Substrate poling effects are investigated, and a magnetoelectric coupling is demonstrated.

• Received 3 August 2012

DOI:https://doi.org/10.1103/PhysRevB.86.144416