Bi3.4Eu0.6Ti3O12/Ni0.7Cu0.3Fe2O4 films annealed under different atmosphere with enhanced magnetoelectric coupling effect

The single Bi4-xEuxTi3O12 and Ni1-xCuxFe2O4 films were prepared via spin-coating method. The composite films of the Bi3.4Eu0.6Ti3O12/Ni0.7Cu0.3Fe2O4, annealed under N2, air and O2, were also prepared via the same method. Compared with the films of Bi4Ti3O12, the films of the Eu-doped Bi4Ti3O12 (Bi4-xEuxTi3O12) exhibit enhanced ferroelectricity. And when x is equal to 0.6, the films of Bi4-xEuxTi3O12 show optimal ferroelectricity. Compared with the undoped NiFe2O4 film, in the films of Ni1-xCuxFe2O4, the doping of Cu2+ enhances ferromagnetism. And when x is equal to 0.3, the Ni1-xCuxFe2O4 films exhibit optimal ferromagnetism. For the composite films of Bi3.4Eu0.6Ti3O12/Ni0.7Cu0.3Fe2O4, annealing atmosphere has a significant impact on the magnetoelectric properties. In comparison with the composite films annealed under N2 and air, the composite films annealed under O2 exhibit optimum ferroelectricity (saturation polarization being 26.3 μC·cm−2), ferromagnetism (saturation magnetization being 385.6 emu·cm−3) and enhanced magnetoelectric coupling effect (magnetoelectric voltage coefficient being 86.4 mV·(cm·Oe)−1). This is beneficial for the applications in magnetoelectric functional devices.