Strain-induced phase transition at the surface of epitaxial La0.65Sr0.35MnO3 films

Abstract

The strong coupling between lattice, electron and spin systems in perovskite manganites along with symmetry breaking at interfaces could lead to inherently different electronic and structural phases at the surface of thin manganite films. To study whether the surface reconstruction can be tuned by epitaxy strain, we employed Surface-Enhanced Raman Spectroscopy (SERS) on La0.65Sr0.35MnO3 (LSMO) thin films epitaxially grown on LaAlO3 substrates. A moderate compressive strain (ε < 1 %) did not change the surface state as compared to that found in unstrained LSMO/MgO(200) films. In contrast, a strong in-plane compressive strain (2 < ε < 3.4 %) stabilizes a novel phase at the surface, characterized by a unique SERS spectrum, which reveals a phase transition at T* = 220 K accompanied by an anomalously strong hardening of the Jahn-Teller mode.