  By moving individual Fe-Porphyrin-based molecules with the tip of Scanning
Tunneling Microscope in the vicinity of a Br-atom containing elbow of the
herringbone-reconstructed Au(111), we reversibly and continuously control their
magnetic state. Several regimes are obtained experimentally and explored
theoretically: from the integer spin limit, through intermediate magnetic
states with renormalized magnetic anisotropy, until the Kondo-screened regime,
corresponding to a progressive increase of charge fluctuations and mixed
valency due to an increase in the interaction of the molecular Fe states with
the substrate Fermi sea. Our results open a route for the realization, tuning
and experimental studies of novel quantum magnetic states in molecule-surface
hybrids.
