Two-Dimensional Organometallic Kondo Lattice with Long-Range Antiferromagnetic Order

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). Low-temperature 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.