Interfacial characteristics and multiferroic properties of ion-doped BiFeO3/NiFe2O4 thin films

Multi-ion doped BiFeO3/NiFe2O4 bilayered thin films were successfully prepared on fluorine-doped SnO2/glass (SnO2:F) substrates by sol-gel method. The crystalline structure, leakage current, interfacial characteristics, and multiferroic properties were investigated in detail. The results of Rietveld refinement showed that the structure of BSrSFMC layer is transformed from rhombohedral to tetragonal structure by the means of ion-doping. The difference of leakage current density of the BSrSFMC/NiFe2O4 (NFO) bilayered films of the -40V to 40V and 40V to -40V are 0.32 x 10(-5) and 1.13 x 10(-5) A/cm(2), respectively. It was observed that there are obvious interface effects between BSrSFMC and NFO layers, which will cause the accumulation of space charges and the establishment of built-in internal electric field (E-I) at the interface. Therefore, different E-I directions will affect the dipoles reversal and migration of carriers in the BSrSFMC layer, which will result in different values of transient current with the same applied voltage in the opposite directions. The larger coercive field (E-c similar to 750 kV/cm) of BSrSFMC/NFO film indicated that there is a tensile stress at the interface between BSrSFMC and NFO layers, making the polarization difficult. These results showed that the above interesting phenomena of the J-V are closely related to the interface effects between the layer of BiFeO3 and NiFe2O4. Published by AIP Publishing.