Effect of induced strain by substrate orientation on magnetic properties in BaTiO3/La0.7Sr0.3MnO3 bilayers

Hybrid multiferroics composed of ferromagnetic (FM) / ferroelectric (FE) heterostructures offer a possible route to design artificial multiferroic material exhibiting, for example, magnetoelectric coupling. We have grown BaTiO3 (100 nm)/ La2/3Sr1/3MnO3 (25 nm) bilayers on (001)-, (110)-, and (111)-oriented SrTiO3 substrate to study the induced strain influence in their magnetic properties. From structural characterization by x-ray analysis we found that La2/3Sr1/3MnO3 (LSMO) layer grew epitaxially strained, whereas BaTiO3 (BTO) film grew relaxed with lattice parameter close to that for single film. The magnetic measurements show a ferromagnetic order for all bilayers at room temperature with a Curie temperature TC∼350 K exhibiting a slight decrease of the magnetic properties (MS, HC and TC) of the bilayers in comparison with those for the La2/3Sr1/3MnO3 film. These variations could be associated to strained/relaxed regions induced by substrate orientation, and dislocation formation close to BTO/LSMO interface, among others phenomena. The magnetization mechanism was studied using the Berger model, where a critical β exponent ∼ 0.25 was found for all LSMO films in different STO orientations, which agrees with the tricritical point model. However, we found a β=0.283 only for the bilayer deposited on (001)STO substrate that coincides with previous reports for YMnO3 multiferroic materials. This behavior is not observed neither in the bilayer grown on (110) STO or (111) STO and displays indirectly a possible magnetoelectrical coupling in this configuration.