Epitaxially Stabilized EuMoO₃: A New Itinerant Ferromagnet

Synthesizing metastable phases often open new functions in materials, but it is a challenging topic. Thin film techniques have advantages to form materials which do not exist in nature since nonequilibrium processes are frequently utilized. In this study, we successfully synthesize an epitaxially stabilized new compound of perovskite Eu²⁺Mo⁴⁺O₃ as a thin film form by a pulsed laser deposition. The analogous perovskite SrMoO₃ is a highly conducting paramagnetic material, but Eu²⁺ and Mo⁴⁺ are not compatible in equilibrium, and a previous study found that the more stable pyrochlore Eu₂³⁺Mo₂⁴⁺O₇ prefers to form. By using isostructural perovskite substrates, the gain of the interface energy between the film and the substrate stabilizes the matastable EuMoO₃ phase. This compound exhibits high conductivity and large magnetic moment, originating from Mo 4d² electrons and Eu 4f⁷ electrons, respectively. Our result indicates the epitaxial stabilization is effective not only to stabilize crystallographic structures but also to form a new compound which contains unstable combinations of ionic valences in bulk form