Electric-Field Control of Oxygen Vacancies and Magnetic Phase Transition in a Cobaltite/Manganite Bilayer

Manipulation of oxygen vacancies (V o) in single oxide layers by varying the electric field can result in significant modulation of the ground state. However, in many oxide multilayers with strong application potentials, e.g., ferroelectric tunnel junctions and solid-oxide fuel cells, understanding V o behavior in various layers under an applied electric field remains a challenge, owing to complex V o transport between different layers. By sweeping the external voltage, a reversible manipulation of V o and a corresponding fixed magnetic phase transition sequence in cobaltite/manganite (SrCoO_3-x/La_0.45Sr0_0.55MnO_3-y) hetero-structures are reported. The magnetic phase transition sequence confirms that the priority of electric-field-induced V o formation or annihilation in the complex bilayer system is mainly determined by the V o formation energies and Gibbs free-energy differences, which is supported by theoretical analysis. We not only realize a reversible manipulation of the magnetic phase transition in an oxide bilayer but also provide insight into the electric-field control of V o engineering in heterostructures.