No abstract

Two-dimensional networks of spins are fascinating both for the study of low-dimensional magnetism and for the prospects in molecular quantum devices. Here we have fabricated a 2D supramolecular lattice consisting of manganese phthalocyanine (MnPc) on Ag(111). Lowtemperature scanning tunneling microscopy/spectroscopy (STM/STS) and density functional theory (DFT) calculations are applied to study the magnetic state and the electronic structure evolution from the isolated molecule to the fully 2D self-assembled molecular network. It is found that the magnetic Kondo resonance on the Mn ion is not affected by the increasing molecular 2D coordination, whereas an unusual extension of the Kondo resonance over the MnPc molecules provides additional evidence for the magnetic polarization of the ligand. Both STS and ab initio electronic structure calculations demonstrate the formation of an underscreened 2D Kondo lattice of MnPc molecules that are prone to long-range antiferromagnetic order. A checkerboard configuration of the molecular spin density is formed above the Ag(111) surface as a result of an indirect exchange interaction mediated by the silver substrate.

The vibrational excitation related transport properties of a manganese phthalocyanine molecule suspended between the tip of a scanning tunneling microsope (STM) and a surface are investigated by combining the local manipulation capabilities of the STM with inelastic electron tunneling spectroscopy. By attachment of the molecule to the probe tip, the intrinsic physical properties similar to those exhibited by a free standing molecule become accessible. This technique allows one to study locally the magnetic properties, as well as other elementary excitations and their mutual interaction. In particular a clear correlation is observed between the Kondo resonance and the vibrations with a strong incidence of the Kondo correlation on the thermopower measured across the single-molecule junction.