Raman study of the vibration eigenmodes of CePt5 films on Pt(111)

Abstract

The surface intermetallic rare-earth compound CePt5 in the range of few unit cells has a high relevance in the field of Kondo- and heavy fermion physics. Besides, it shows an intriguing crystal-lattice development, which is expected to be reflected in its vibration modes. We present a temperature-dependent vibrational frequency- and symmetry analysis by polarized Raman spectroscopy on CePt5 films and for comparison isostructural LaPt5 films. Three CePt5 eigenmodes with characteristic symmetry properties occur with frequencies around 100, 120, and 130 cm−1. By group-theoretical analysis and from the evolution of their intensities they are attributed to the mode of the bulklike CePt5 film and E2- and A1 modes of a symmetry-reduced CePt5 top layer, respectively. Thus, they confirm the model, derived by low-energy electron diffraction, of this material system regarding structure and strain development. The LaPt5 vibration peaks are qualitatively similar. Slight frequency shifts of the latter are mainly attributed to a modified strain development. Finally, an anomalous low-temperature frequency shift occurs for the A1 mode of the CePt5 top layer, which might indicate an interaction with the 4f electron system.