  Kondo effect originates from antiferromagnetic (AFM) s-d coupling between
magnetic impurity and the conduction electron, while it will be totally
quenched in ferromagnetic (FM) regime due to malfunction of spin-flip. We
investigate the possibility of switching on/off Kondo effect by transition of
AFM/FM s-d coupling using 3d-metal phthalocyanine molecule (MPc) on Au(111) as
a model system. A Hamiltonian model is constructed based on the feature of MPc
molecule to show the condition for AFM/FM s-d coupling. The AFM s-d coupling
could transform to FM s-d coupling if the spin state of the lowest unoccupied
orbital changes.
