Microstructure and properties of sol–gel derived PbTiO_3/NiFe_2O_4 multiferroic composite thin film with the two nano-crystalline phases dispersed homogeneously

摘要

Ferroelectric/ferrimagnetic PbTiO_3/NiFe_2O_4 composite thin films with nano-scale PbTiO_3 and NiFe_2O_4 phases homogeneously dispersed in each other were synthesized by sol–gel in situ method. The phase structure and morphology of the composite thin films and their dielectric, ferroelectric and ferromagnetic properties were measured respectively in detail. Results show that the ferroelectric/ferrimagnetic composite thin film with PbTiO_3 and NiFe_2O_4 phases is successfully synthesized at heat-treatment temperature of 850℃. It is significantly isotropic due to the nanometer scale grain size of the constituent PbTiO_3 and NiFe_2O_4 phases. A capacitance of 60–100 pF with a good frequency independence over the conventional applied frequency range, ferroelectric hysteresis loops with the applied electric field of 500 kV/cm, a saturation magnetization higher than 4.8 MT, and a coercive field of 5280A/m with well suitable ferrimagnetic properties are obtained from the thin film with the composition ratio PbTiO_3/NiFe_2O_4 of 50/50 post heat-treated at 850℃. The ferroelectric/ferrimagnetic composite thin film is desirable for multifunctional device application.