Epitaxial Stabilization of the Perovskite Phase in (Sr_1–<i>x</i>Ba_<i>x</i>)MnO₃ Thin Films

A novel mechanism of ferroelectricity driven by off-centering magnetic Mn⁴⁺ ions was proposed in (Sr_1–<i>x</i>Ba_<i>x</i>)­MnO₃, in its ideal perovskite phase, which yields enormous expectations in the search for strong magnetoelectric materials. Still, the desired perovskite phase has never been stabilized in thin films due to its extremely metastable character. Here, we report on a thorough study of the perovskite phase stabilization of (Sr_1–<i>x</i>Ba_<i>x</i>)­MnO₃ thin films, 0.2 ≤ <i>x</i> ≤ 0.5, grown by pulsed laser deposition onto (001)-oriented perovskite substrates. X-ray diffraction measurements and scanning transmission electron microscopy reveal that, under appropriate deposition conditions, the perovskite phase is fully stabilized over the nonferroelectric hexagonal phase, despite the latter being increasingly favored on increasing Ba-content. Moreover, we have managed to grow epitaxial coherent cube-on-cube (Sr_1–<i>x</i>Ba_<i>x</i>)­MnO₃ films upon strains ranging from 0% to 4%. Our results become a milestone in further studying perovskite (Sr_1–<i>x</i>Ba_<i>x</i>)­MnO₃ thin films and pave the way for tailoring ferroic and magnetoelectric properties either by strain engineering or Ba-doping