SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 39: Poster Session: Heterogeneous Catalysis and Surface Dynamics

O 39.5: Poster

Dienstag, 28. März 2023, 18:00–20:00, P2/EG

Surface phase transitions in doped manganite thin films — •Leonard Schüler, Tim Titze, Stefan Mathias, Daniel Steil, and Vasily Moshnyaga — I. Physikalisches Institut, Georg-August-Universität Göttingen

The symmetry breaking at the surface of strongly correlated La_1−xSr_xMnO₃ (LSMO) thin films leads to a modification of orbital occupation compared to the bulk resulting in the formation of intrinsic magnetic and electric surface phases. To obtain a phase diagram of possible surface states, LSMO films with Sr doping over the complete range x = 0 − 1 were prepared by metalorganic aerosol deposition and have been investigated by both surface-enhanced Raman spectroscopy (SERS) and pump-probe optical (SE-PPR) reflectivity. Temperature-dependent SERS reveals magnetic phase transitions by anomalous frequency shifts of the MnO₆ octahedra’s stretching mode resulting from spin-phonon coupling, as well as changes in Mn orbital occupation inferred by enhanced Raman activity of vibrational Jahn-Teller modes at the surface. Furthermore, ultrafast dynamics studied by SE-PPR reveals a surface phase transition, which is not present in the bulk LSMO.