Observation of unexpected uniaxial magnetic anisotropy in La(2/3)Sr(1/3)MnO(3) films by a BaTiO(3) overlayer in an artificial multiferroic bilayer

We studied in detail the in-plane magnetic properties of heterostructures based on a ferroelectric BaTiO(3) overlayer deposited on a ferromagnetic La(2/3)Sr(1/3)MnO(3) film grown epitaxially on pseudocubic (001)-oriented SrTiO(3), (LaAlO(3))(0.3)(Sr(2)TaAlO(6))(0.7) and LaAlO(3) substrates. In this configuration, the combination of both functional perovskites constitutes an artificial multiferroic system with potential applications in spintronic devices based on the magnetoelectric effect. La(2/3)Sr(1/3)MnO(3) single layers and BaTiO(3)/La(2/3)Sr(1/3)MnO(3) bilayers using the pulsed-laser deposition technique. We analyzed the films structurally through X-ray reciprocal space maps and high-angle annular dark field microscopy, and magnetically via thermal demagnetization curves and in-plane magnetization versus applied magnetic field loops at room temperature. Our results indicate that the BaTiO(3) layer induces an additional strain in the La(2/3)Sr(1/3)MnO(3) layers close to their common interface. The presence of BaTiO(3) on the surface of tensile-strained La(2/3)Sr(1/3)MnO(3) films transforms the in-plane biaxial magnetic anisotropy present in the single layer into an in-plane uniaxial magnetic anisotropy. Our experimental evidence suggests that this change in the magnetic anisotropy only occurs in tensile-strained La(2/3)Sr(1/3)MnO(3) film and is favored by an additional strain on the La(2/3)Sr(1/3)MnO(3) layer promoted by the BaTiO(3) film. These findings reveal an additional mechanism that alters the magnetic behavior of the ferromagnetic layer, and consequently, deserves further in-depth research to determine how it can modify the magnetoelectric coupling of this hybrid multiferroic system.