Regensburg 2025 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 33: Poster Graphene: Electronic Structure and Excitations
O 33.7: Poster
Dienstag, 18. März 2025, 13:30–15:30, P3
Magnetic MnPc molecules adsorbed on epitaxial graphene — •James Oyuga1, Nhung Nguyen1, Uwe Gerstmann2, Eva Rauls3, Julian Koch1, and Christoph Tegenkamp1 — 1Institut für Physik, TU Chemnitz, Germany — 2Theoretische Physik, Universität Paderborn, Germany — 3Department of Mathematics and Physics, University of Stavanger, Norway
Phthalocyanines (Pc) are prototype molecules hosting magnetic ions. When adsorbed on surfaces, the spin state of the molecules is influenced by the substrate. In a combined experimental and theoretical study, we investigated this influence for the case of MnPc molecules adsorbed on monolayer graphene/SiC(0001) using STM, magnetotransport and theoretical DFT modeling. The STM measurements showed that the self-assembly of the MnPc molecules results in an almost defect-free monolayer with a (4×2) unit cell accommodating 8 MnPc molecules. The DFT modeling revealed that the structure and thereby the spin states of the molecules are decisively influenced by the substrate. In the gas phase the MnPc molecules are symmetrically bended with a spin state of S=3/2. However, on an epitaxial graphene monolayer this is changed into an even mixture of flat molecules with an S=5/2 spin state and upward bended molecules with an S=3/2 spin state. This mixture allows for a denser arrangement of the molecules in a (4×2) unit cell, that is commensurable with both the graphene layer and the underlying SiC substrate. The impact of such molecular structures towards transport in epitaxial monolayer graphene is quantified by magneto transport experiments analyzing the weak (anti) localization.
Keywords: MnPc; graphene; magnetic; molecules