TEM imaging and in-situ EELS study of multiple ferroic transitions in LaCoO3*

The perovskite oxide LaCoO3 has attracted increasing attention due to its reported room-temperature ferroelastic behavior, and a ferromagnetic transition observed at around 90K in epitaxially strained thin films. To advance our understanding of these nanoscale properties of LaCoO3, a combination of analytical TEM techniques, including the atomic-resolution Z-contrast imaging and electron energy-loss spectroscopy in combination with in-situ cooling experiments have been used to study the relationship of the multiple ferroic transitions in bulk LaCoO3. In particular, we find that the bulk LaCoO3 samples compressed above the coercive stress exhibit ferromagnetic transitions, similar to the ferromagnetic behavior of the epitaxially strained LaCoO3 thin film. While the bulk LaCoO3 samples compressed below the coercive stress do not exhibit any ferromagnetic transitions down to 5K. We will further correlate this ferromagnetic property to the ferroelastic property of LaCoO3, and show how the strain of the LaCoO3 affects the ferromagnetic property of the sample.