Jahn-Teller reconstructed surface of the doped manganites shown by means of surface-enhanced Raman spectroscopy

Abstract

We report direct evidence of the theoretically predicted electron-rich surface of doped perovskite manganites La0.7A0.3MnO3(A=Ca, Sr) by means of surface-enhanced Raman spectroscopy. The required Au nanoparticles were grown on top of thin manganite films by the metalorganic aerosol deposition technique, which provides a stable oxygen atmosphere and prevents deoxygenation effects. The acquired surface-enhanced Raman spectra of rhombohedral La0.7Sr0.3MnO3 thin films reveal the symmetry-forbidden Jahn-Teller stretching modes demonstrating the predicted symmetry breaking at the surface and fallback into the orthorhombic (Pnma) structure. This results in a unique Jahn-Teller reconstructed surface structure, which limits the capabilities of mixed-valence manganites in spintronic applications, but will be highly favorable for catalytic reactions.