Control of Oxygen Vacancy Ordering in Brownmillerite Thin Films via Ionic Liquid Gating

Oxygen defects and their atomic arrangements play a significant role in the physical properties of many transition metal oxides. The exemplary perovskite SrCoO 3-δ ( P- SCO) is metallic and ferromagnetic. However, its daughter phase, the brownmillerite SrCoO 2.5 ( BM- SCO), is insulating and an antiferromagnet. Moreover, BM- SCO exhibits oxygen vacancy channels (OVCs) that in thin films can be oriented either horizontally ( H -SCO) or vertically ( V -SCO) to the film's surface. To date, the orientation of these OVCs has been manipulated by control of the thin film deposition parameters or by using a substrate-induced strain. Here, we present a method to electrically control the OVC ordering in thin layers via ionic liquid gating (ILG). We show that H -SCO (antiferromagnetic insulator, AFI) can be converted to P -SCO (ferromagnetic metal, FM) and subsequently to V -SCO (AFI) by the insertion and subtraction of oxygen throughout thick films via ILG. Moreover, these processes are independent of substrate-induced strain which favors formation of H -SCO in the as-deposited film. The electric-field control of the OVC channels is a path toward the creation of oxitronic devices.