Effect of strain on the ferroelectric properties in epitaxial perovskite titanate thin films grown on ferromagnetic CoFe_2O_4 layers

摘要

A BaTiO_3/CoFe_2O_4 heterostructure was fabricated by laser molecular beam epitaxy. The effects of strain on the microstructures, domain morphologies and ferroelectric properties of BaTiO_3 thin films were studied systematically. Ferroelectric properties in a 40-nm-thick BaTiO_3 film were suppressed owing to a reduced tetragonality induced by the strain between BaTiO_3 and the underlying CoFe_2O_4. For a 100-nm-thick film, BaTiO_3 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 BaTiO_3 can significantly affect the interfacial strain and hence the ferroelectric properties of the BaTiO_3/CoFe_2O_4 heterostructure.