Effects of NiFe2O4 on magnetoelectric coupling effect of BiFeO3 thin films

•With increasing x, the average size of the crystal grains of BiFeO3 diminishes gradually.•With increasing x, the leakage current density in composite thin films decreases while the remnant polarization increases.•The calculated results indicated that BiFeO3 also contributed magnetic moment to the composite films.•The decreasing crystal grain size of the BiFeO3 was responsible for ferromagnetism and the enhanced magnetoelectric coupling effect.

Multiferroic composite thin films with composition (1−x)BiFeO3–xNiFe2O4 (x=0.00, 0.10, 0.15, 0.20, 0.25, and 0.30) were prepared by chemical solution deposition(CSD). The results show that with increasing x, the average size of the crystal grains of BiFeO3 diminishes gradually, and the leakage current density in composite thin films decreases while the remnant polarizations increases. The calculated results for the ferromagnetic contribution of the NiFe2O4 indicated that BiFeO3 also contributed magnetic moment to the composite films. On comparing the grain sizes and magnetic measurement results of the composite thin films with x=0.20 and 0.25, we found that the decreasing crystal grain size of the BiFeO3 was responsible for ferromagnetism and that the enhanced magnetoelectric coupling effect in composite thin films was also an important factor.