Low-Temperature Topotactic Control of a Double Exchange Interaction in an La0.5Sr0.5CoO3 Oxygen Sponge Facilitates the Development of Ultra-Sensitive and Stable Correlated Oxygen Sensors

Abstract

Exotic oxygen-driven control of quantum-mechanical properties has attracted considerable attention for the oxygen sensors since it can give superior sensitivity to conventional sensors. Here, it is shown that La0.5Sr0.5CoO3 oxygen sponges simultaneously exhibit a huge change of resistance by three orders of magnitude, a reversible modulation of ferromagnetic ordering, stability, and reusability when the films in vacuum and oxygen is successively annealed. The correlated oxygen sensors work at lower temperatures (175-250 degrees C) and within a shorter timeframe (8-30 minutes) compared with conventional oxygen sensors working above 500 degrees C. The oxygen-driven control starts softly via oxygen-vacancy-driven relaxation of double exchange interaction in the perovskite La0.5Sr0.5CoO3, which is further amplified with the topotactic transition into brownmillerite La0.5Sr0.5CoO2.5. This more facile transition is attributable to oxygen-driven filling of correlated electrons in Co 3d-orbitals and successive destabilization of CoO6 octahedra into CoO4 tetrahedra. The La0.5Sr0.5CoO3 oxygen sponges with ionic-electric-magnetic coupling constitute a proof-of-principle demonstration that ultra-sensitive and stable oxygen sensors can be achieved.