Interfacial characteristics and multiferroic properties of ion-doped BiFe03/NiFe_2O_4 thin films

摘要

Multi-ion doped BiFeO_3/NiFe_2O_4 bilayered thin films were successfully prepared on fluorine-doped SnO_2/glass (SnO_2: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 rhombohe-dral to tetragonal structure by the means of ion-doping. The difference of leakage current density of the BSrSFMC/NiFe_2O_4 (NFO) bilayered films of the -40 V to 40 V and 40 V to -40 V 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 (£/) at the interface. Therefore, different E_1 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~750kV/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 BiFeO_3 and NiFe_2O_4.