Raman measurements on thin films of the La0.7Sr0.3MnO3 manganite: a probe of substrate-induced effects
Coherentia CNR-INFM and Dipartimento di Fisica, Università “La Sapienza”, P.le A. Moro 4, 00187 Roma, Italy
2 Coherentia CNR-INFM and Dipartimento di Ingegneria Meccanica, Universita' di Roma Tor Vergata, via del Politecnico 1, 00133 Roma, Italy
Corresponding author: a email@example.com
Published online: 16 December 2005
We report on a Raman study of the phonon spectrum of La 0.7Sr0.3MnO3 thin films epitaxially grown on LaAlO3. The spectrum, as a function of film thickness d, does not change over the 1000–100 Å range, whereas a strong hardening of the phonon frequencies of both bending and stretching modes is apparent in ultra-thin films (d<100 Å) where substrate-induced effects are remarkable. This behaviour, which appears to be related with the measured d-dependence of the insulator-to-metal transition temperature, is ascribed to co-operative effects of MnO6 octahedra rotation and charge-localization. Raman spectroscopy proves to be a simple and powerful tool to monitor subtle structural modifications hardly detectable with conventional diffraction techniques in ultra-thin films.
PACS: 63.20.-e – Phonons in crystal lattices / 78.20.-e – Optical properties of bulk materials and thin films / 78.30.-j – Infrared and Raman spectra
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2005