The ability to manipulate oxygen anion defects rather than metal cations incomplex oxides can facilitate creating new functionalities critical foremerging energy and device technologies. However, the difficulty in activatingoxygen at reduced temperatures hinders the deliberate control of importantdefects, oxygen vacancies. Here, strontium cobaltite (SrCoOx) is used todemonstrate that epitaxial strain is a powerful tool for manipulating theoxygen vacancy concentration even under highly oxidizing environments and atannealing temperatures as low as 300 C. By applying a small biaxial tensilestrain (2%), the oxygen activation energy barrier decreases by ~30%, resultingin a tunable oxygen deficient steady-state under conditions that would normallyfully oxidize unstrained cobaltite. These strain-induced changes in oxygenstoichiometry drive the cobaltite from a ferromagnetic metal towards anantiferromagnetic insulator. The ability to decouple the oxygen vacancyconcentration from its typical dependence on the operational environment isuseful for effectively designing oxides materials with a specific oxygenstoichiometry.
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