Abstract
Single molecule magnets (SMMs) play an important role in molecular spintronics. They are characterized by a high-spin ground state with zero-field splitting that leads to long magnetization relaxation times. A relevant class of molecules are the lanthanide double-decker phthalocyanines (LnPc2) with only one metal atom in the center of two organic Pc ligands. The late-Ln complexes TbPc2 and DyPc2 are known to be SSMs with relatively high blocking temperatures in bulk or diluted bulk samples. Hence, NdPc2 is a promising candidate for being an SMM, but was not yet experimentally investigated. For envisaged spintronics applications it is important to understand the molecule-substrate interaction and its impact on the electronic and magnetic properties. Here, we study single adsorbed NdPc2 by means of low-temperature scanning tunneling microscopy and spectroscopy (STM and STS) and density-functional theory (DFT) calculations.
The NdPc2 molecules were home-made and in-situ evaporated from a Knudsen cell on clean metallic surfaces such as Cu(100), Au(111), and Fe/W(110). We find that a significant fraction of the NdPc2 decomposes into two single-decker Pc. The decomposition probability is strongly substrate dependent. STS-spectra indicate that a stronger substratemolecule interaction leads to enhanced charge transfer, which strengthens the intramolecular electrostatic bonding and thus reduces the decomposition probability.
For the NdPc2/Cu(100) system we record energy dependent topography images, differential conductivity (dI/dV) maps, and I(V) spectroscopy curves for different molecular sites. Spatially and energetically resolved orbitals are compared to ab-initio DFT calculations of NdPc2/Cu(100), which allow identifying them with specific electronic states of the molecule-substrate complex. In particular we demonstrate for the first time that the spinpolarized Nd 4f-states are involved in charge transport through the early-Ln complex NdPc2 absorbed on Cu(100). This opens up prospects for electrical manipulation and detection of the molecular spin state, providing the basis for all-electrically controlled device concepts in molecular spintronics.
Coffee and tea will be served 20 minutes prior to the seminar.