Coupling interaction in nanostructured piezoelectric/magnetostrictive multiferroic complex films

Nanostructured piezoelectric/magnetostrictive multiferroic composite films with a strong coupling between ferroelectric and ferromagnetic order parameters are attracting extensive attention. The coupling interaction in the nanostructured multiferroic film should be different from that in bulk composite due to large residual stress/strain in the film. In this paper, the magnetoelectric coefficient of the nanostructured BaTiO3–CoFe2O4 multiferroic films was studied by using the modified constitutive equations where the influence of residual stress and spontaneous polarization was considered. Our results show that the 1-3-type BaTiO3–CoFe2O4 composite films could exhibit a strong coupling between ferroelectric and ferromagnetic order parameters, while the 2-2-type nanostructured composite films were found to produce a much less coupling interaction. Magnetoelectric effect of the films is dependent on composition and residual stress in films, and temperature. The calculations are in broad agreement with the experimental results available.