Theory of the magnetoelectric effect in multiferroic epitaxial Pb(Zr0.3,Ti0.7)O3/La1.2Sr1.8Mn2O7 heterostructures

In this paper, a model of multiferroic heterostructure is constructed by growing an epitaxial piezoelectric film on a magnetostrictive layered manganite single crystal. By considering the efficient mechanical coupling at the interface, the magnetoelectric (ME) effect, especially for magnetically induced polarization of the multiferroic film, has been theoretically studied by combining the modified constitutive equations with the Landau-Ginsberg-Devonshire (LGD) thermodynamic theory, where the influence of residual strain, spontaneous polarization and magnetostriction were considered. The calculated results show that large magnetic field-induced polarization could be produced in ferroelectric film due to a gigantic magnetically induced in-plane constraint and an enhanced elastic coupling interaction, which is consistent with Green's function technique analysis. The ME effect peaks at the ferromagnetic transition temperature of the manganite. Comparison with experimental data of multilayered samples reveals good interface coupling between the magnetostrictive phase substrate and epitaxial ferroelectric film. The calculations are in broad agreement with the available experimental results.