Topotactic Phase Transition in Epitaxial La _0.7 Sr _0.3 MnO _3‐δ Films Induced by Oxygen Getter Assisted Thermal Annealing

Abstract Oxygen vacancies play a crucial role in controlling the physical properties of complex oxides. In La _0.7 Sr _0.3 MnO _3‐δ , the topotactic phase transition from Perovskite (PV) to Brownmillerite (BM) can be triggered, e.g., via oxygen removal during thermal annealing. Here, a very efficient thermal vacuum annealing method is reported using aluminum as an oxygen getter material. The topotactic phase transition is characterized by X‐ray Diffraction, which confirms a successful transition from PV to BM in La _0.7 Sr _0.3 MnO _3‐δ thin films grown via physical vapor deposition. The efficiency of this method is confirmed using La _0.7 Sr _0.3 MnO _3‐δ micron‐sized bulk powder. The accompanying transition from the original Ferromagnetic (FM) to an Antiferromagnetic (AF) state and the simultaneous transition from a metallic to an insulating state are characterized using Superconducting Quantum Interference Device (SQUID) magnetometry and Alternating Current (AC) resistivity measurements, respectively. The near‐surface manganese oxidation states are probed by synchrotron X‐ray Absorption Spectroscopy. Moreover, X‐ray Reflectivity, Atomic Force Microscopy, and Scanning Transmission Electron Microscopy reveal surface segregation and cation redistribution during the oxygen getter‐assisted annealing process.