Abstract
Topotactic phase transitions induced by changes in the oxygen vacancy concentration can largely alter the physical properties of complex oxides, including electronic and magnetic phases, while maintaining the structural integrity of the crystal lattice. An oxygen-vacancy-induced topotactic phase transition from perovskite (PV) to brownmillerite (BM) is achieved in epitaxial La0.6Sr0.4CoO3−δ (LSCO) thin films. Two novel intermediate states with different oxygen content are identified by X-ray diffraction, which involves a single-phase reduced PV state and a mixed state of co-existing PV and BM. The combination of depth-sensitive polarized neutron reflectometry (PNR) and Rutherford backscattering (RBS) allows a quantitative determination of magnetization and the mean oxygen content in all states, revealing a continuous transition from La0.6Sr0.4CoO2.97 to La0.6Sr0.4CoO2.5. BM formation is observed for an LSCO layer with an oxygen content of 2.67, while the magnetic and electronic transition already occurs for a layer with a higher oxygen content of 2.77 (and above) and in the absence of a BM signature. These results demonstrate that the physics of electronic metal-to-insulator transition (MIT), magneticferromagnet-to-non-ferromagnet transition (FM-to-non-FM), and structural PV-to-BM phase transition should be considered within the framework of separate but interrelated processes.
Original language | English |
---|---|
Journal | Advanced Functional Materials |
DOIs | |
State | Accepted/In press - 2024 |
Funding
S.H., O.P., and F.G. gratefully acknowledge collaborative project funding by Forschungszentrum Jülich within the Helmholtz Association. This research used resources at the Spallation Neutron Source, a Department of Energy Office of Science User Facility operated by the Oak Ridge National Laboratory. The authors thank H. Ambaye for his assistance in preparation for the neutron experiment. Notice: This manuscript has been authored by UT‐Battelle, LLC, under Contract No. DE6AC0500OR22725 with the U.S. Department of Energy. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation hereon. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe‐publicaccess‐plan ).
Keywords
- electronic and magnetic phase transitions
- ionotronics
- oxide electronics
- polarized neutron reflectivity
- topotactic phase transition