Regensburg 2016 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 12: Postersession DS

DS 12.15: Poster

Montag, 7. März 2016, 17:00–19:00, Poster A

Raman spectroscopy of crystal field excitations and vibration modes in CePt5 surface layers — •Benedikt Halbig1, Utz Bass1, Martin Zinner2, Kai Fauth2, and Jean Geurts11Universität Würzburg, Exp. Physik III, Würzburg, Germany — 2Universität Würzburg, Exp. Physik II, Würzburg, Germany

The rare-earth compound CePt5 is highly relevant for heavy-fermion quasiparticles and Kondo physics. The Ce 4f electron energy levels are split by the crystal field of their neighbor atoms by about 20 meV. We report on the detection of this splitting by Raman spectroscopy from electron crystal field excitations (CFE) in CePt5 surface layers with thicknesses between 2 and 16 unit cells, grown in UHV by annealing-induced alloying on Pt(111) substrates. For reference, LaPt5 layers were employed, i.e. without 4f electrons. The crystal lattice consists of alternating CePt2- (LaPt2-) and Pt-kagome layers, whereas the surface is a hexagonal Pt layer. Depending on the CePt5 layer thickness, up to three peaks in the insitu UHV Raman spectra at T≈20K are identified as CFE of the 4f electron because of their absence for the LaPt5 reference samples. Their energies are 17meV, 23meV and 25meV. From their individual thickness-dependent intensity behavior, we assign them to CFE transitions at the Pt(111)-CePt5 interfaces, in the CePt5 layer, and at the CePt5-Pt surface layer, respectively. Besides, we observe three additional Raman peaks: one is assigned to the E2g vibration mode of the CePt5 lattice, the other two to the near-surface part of the CePt5 layer, whose symmetry is reduced by shifted Pt layers. Equivalent vibration peaks occur for the LaPt5 reference.

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