The possibility of controlling magnetic properties through external parameters such as electric field or structural variations is a fascinating field of research both for the interplay of several physical properties between different materials  and for possible technological implementations . Indeed, multiferroic heterostructures, integrating individual ferroelectric and ferromagnetic materials, are gaining interest in the scientific community as possible spintronic devices . Within this field, a promising and deeply studied class of materials is that of perovskite metal oxides: they are known to be strongly correlated systems, in which charge and spin degrees of freedom are entangled, and their physical properties can be engineered by doping and strain .
In the present work a La0.65Sr0.35MnO3 (LSMO) thin film (30 unit cells thick) was grown on a BaTiO3 (BTO) ferroelectric single crystal by Molecular Beam Epitaxy, and its magnetic properties were studied with X-ray Magnetic Circular Dichroism (XMCD) as a function of temperature and of the polarization state of the substrate (pristine and after application of an out-of-plane electric field).
The results show that the structural phase transitions of the substrate affect the magnetic response of LSMO in a sensible way: with the substrate in the unpolarized state, a dichroic effect in the Mn L edges is observed only when BTO is in the orthorombic phase (temperature between 180 and 280 K) and not when it is in the tetragonal (at room temperature) or rhombohedral (below 180 K) phases. Furthermore, out-of-plane polarization of the substrate induces the appearance of ferromagnetic ordering in the LSMO film at room temperature, which was absent in the unpolarized state. Ab-initio simulations suggest that in the strain condition studied there is a tight competition between ferromagnetic and antiferromagnetic ordering in the LSMO.
These observations can be explained as the effects of a strong interplay between the structural properties of the BTO substrate, resulting in variations of the LSMO thin layer strain, and the magnetic properties of the latter.
 H.Y. Hwang, Y. Iwasa et al – Nat. Mat. 11 (2012) 103
 F. Matsukura, Y. Tokura and H. Ohno – Nat. Nanotech. 10 (2015) 209
 J.M. Hu, L.Q. Chen and C.W. Nan - Adv. Mat. 28 (2016) 15
 A.M. Haghiri-Gosnet and J.P. Renard – Jour. Phys D: Appl. Phys 36 (2003) R127