A Route for Fabricating Epitaxial Europium Titanate Film in a Wide Strain Range

Strain engineering of antiferromagnetic-paraelectric perovskite oxides with strong spin-phonon coupling presents a route to induce a multiferroic phase with simultaneous large electric polarization as well as strong magnetoelectric coupling. Such a multiferroic phase is of great importance as it offers real transformative technological applications where one can manipulate the large electric polarization by a magnetic field and the magnetic order by an electric field. However, difficulty in the thin-film fabrication of such materials in the pure phase and requirement of large epitaxial strain to induce multiferroicity present a big challenge for experimental realization of the multiferroic phase in these materials. Here, for the first time, we report the successful thin-film growth of one such material, i.e., europium titanate (EuTiO3), in a wide strain range (from -2.89 to +2.15%). The upper limits of this strain range are substantially higher than the minimum strain value (-1.2 and +0.75% in the case of compressive and tensile strains, respectively) required to induce the multiferroic phase in this material. The strain-dependent magnetic phases of these films, as inferred by detailed magnetic characterization, are well in accordance with the theoretically predicted phase diagram. Importantly, our thin-film growth methodology is relatively simple and time efficient, and growth conditions are easily achievable in any thin-film growth chamber. Our work paves the way for technological exploitation of such multiferroic phases as well as exploring the concepts such as multiferroic quantum criticality and dynamical multiferroicity.