Raman scattering study of La0.7Sr0.3MnO3/SrTiO3 multilayers

We report room-temperature Raman scattering results on perovskite-type [(La0.7Sr0.3MnO3)(m)/(SrTiO3)(n)](15) multilayers, in and n being the thicknesses of layers alternated 15 times. Distinct changes in the Raman spectra for different n and in have been analysed in the light of structural modifications and point to a tensile-strain-induced rhombohedral-to-orthorhombic phase transition in the La0.7Sr0.3MnO3 (LSMO) layers. As a matter of fact, the presented results provide anew structural basis for the earlier proposed magnetic phase separation model. The present work validates tensile strain as an important variable in thin films, which not only allows us to distort the perovskite structure within a crystallographic space group but can readily induce a transition towards another space group and its related physical properties. As shown in this study, the fabrication of superlattice materials then constitutes a powerful method to stabilize such artificial crystal structures (here artificial orthorhombic LSMO at 300 K) over a greater overall thickness than would be possible in single films.