Effect of strain on the ferroelectric properties in epitaxial perovskite titanate thin films grown on ferromagnetic CoFe2O4 layers

A BaTiO3/CoFe2O4 heterostructure was fabricated by laser molecular beam epitaxy. The effects of strain on the microstructures, domain morphologies and ferroelectric properties of BaTiO3 thin films were studied systematically. Ferroelectric properties in a 40-nm-thick BaTiO3 film were suppressed owing to a reduced tetragonality induced by the strain between BaTiO3 and the underlying CoFe2O4. For a 100-nm-thick film, BaTiO3 exhibits improved the ferroelectric properties with an out-of-plane polarization (2P(r)) of 36.4 mu C cm(-2) and an electric coercivity field of 104 kV cm(-1). The results show that the thickness of BaTiO3 can significantly affect the interfacial strain and hence the ferroelectric properties of the BaTiO3/CoFe2O4 heterostructure. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.