# Topotactic phase transition in epitaxial La0.7Sr0.3MnO3-{\delta} films induced by oxygen getter assisted thermal annealing

## TL;DR

This study demonstrates an efficient oxygen getter-assisted thermal annealing method to induce a topotactic phase transition from Perovskite to Brownmillerite in La0.7Sr0.3MnO3-{ extdelta} films, significantly altering their magnetic and electronic properties.

## Contribution

The paper introduces a novel, highly effective annealing technique using aluminum as an oxygen getter to control phase transitions in complex oxide films.

## Key findings

- Successful PV to BM phase transition confirmed by XRD
- Transition from ferromagnetic to antiferromagnetic state observed
- Metallic to insulating transition characterized by resistivity measurements

## Abstract

Oxygen vacancies play a crucial role in controlling the physical properties of complex oxides. In La0.7Sr0.3MnO3-{\delta}, the topotactic phase transition from Perovskite (PV) to Brownmillerite (BM) can be triggered e.g. via oxygen removal during thermal annealing. Here we report on a very efficient thermal vacuum annealing method 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 La0.7Sr0.3MnO3-{\delta} thin films grown via physical vapor deposition. The efficiency of this method is confirmed using La0.7Sr0.3MnO3-{\delta} 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 is 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.

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Source: https://tomesphere.com/paper/2508.21023