Oxygen Ion Pumping across Atomically Designed Oxide Heterointerfaces

Complex oxide heterointerfaces and heterostructures have demonstrated enormous emergent phenomena over the last decades, attributed to the reconstructions of mis-matched crystalline structure, polarity, and spin ordering across the heterointerfaces. This work employs the heterostructures of La_0.7Sr_0.3MnO₃ and CaFeO_2.5 as model system to demonstrate an interface-specific oxygen migration/reconstruction across the interfaces due to the mismatched chemical potential, which dramatically influences the ferromagnetic and electronic states of La_0.7Sr_0.3MnO₃ layer. Specifically, the alternative stacking of octahedral (O_h) and tetrahedral (T_d) layers in CaFeO_2.5 are used to form two distinct heterointerfaces, namely the O_h-T_d and the O_h-O_h interfaces with the adjacent La_0.7Sr_0.3MnO₃ layer. Interestingly, the oxygen ion migrates toward opposite directions across the interface for these two cases, in which the CaFeO_2.5 layer acts as an “oxygen pump” and manipulates the oxygen contents of its adjacent La_0.7Sr_0.3MnO₃ layers. Such manipulation leads to a dramatically changed ferromagnetic transition temperature for the heterostructure with the O_h-T_d and O_h-O_h interface. This work establishes a feasible and efficient strategy to control the oxygen ionic distribution through atomic-scale interface design and opens up new opportunities to exploit emergent states at the complex oxide heterostructures through selective oxygen ion evolution.