Oxygen Ion Pumping across Atomically Designed Oxide Heterointerfaces

Abstract 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 0.7 Sr 0.3 MnO 3 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 0.7 Sr 0.3 MnO 3 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 0.7 Sr 0.3 MnO 3 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 0.7 Sr 0.3 MnO 3 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.