Study on multiferroic properties in Ni80Fe20/BaTiO3 bilayer films

In this study, we investigated the magnetoelectric coupling effect in Ni80Fe20/BaTiO3 (NiFe/BTO) bilayer films. Two different samples with interface roughnesses of about 5 and 20 nm were synthesized by controlling the BTO deposition rates. The electrostatic force microscope scanning shows an intrinsic surface potential about 0.2 V existing in both NiFe/BTO bilayer films. This phenomenon is due to the bond charge induced by interface dipole moments as the interface-bonding model predicted. The films show good ferroelectric properties, but the hysteresis shows bias asymmetry due to the interface effect. The magnetic coercive fields of NiFe/BTO system increase with the interface roughness. The large magnetoelectric coupling is observed from an irregular change of magnetization near the ferroelectric Curie temperature. The multiferroic properties were enhanced by the interface geometry.