Enhanced Ferromagnetism Induced by Chemical Doping and Epitaxial Strain in La0.8Sr0.2CoO3 Films

The perovskite LaCoO3 and La0.8Sr0.2CoO3 thin films were synthesized successfully by a polymer-assisted deposition method. The structural characterization and thermal decomposition measurements indicate that appropriately increasing the annealing temperature is helpful in improving the film crystallinity. Compared with LaCoO3 films, the Curie temperature is enhanced to a higher temperature in La0.8Sr0.2CoO3 films, which is attributed to the changes in both the valence state and spin state induced by the chemical doping. In addition, a broad transition temperature region is observed in La0.8Sr0.2CoO3 films, revealing the existence of inhomogeneous ground states in this system.