Dynamics of proximity-induced magnetism at cobalt/molecular interfaces

Interfacing ferromagnetic metals with organic molecules is a versatile strategy to control key parameters in magnetic and spintronic technologies. Hybridization between the metal’s surface d orbitals and molecular p orbitals profoundly alters both the interfacial molecular layer and adjacent metal interface atomic layers, causing substantial changes in the magnetic properties of metal/molecule heterostructures. While magnetic modifications within the metallic layer are relatively well understood, the interfacial magnetism remains elusive. Using ultrafast time-resolved magneto-optical spectroscopy, we investigate the magnetic dynamics in such heterostructures and identify a distinct interfacial magnetic component that appears universal across various cobalt/molecule combinations. Our findings reveal a highly anisotropic magnetic layer localized at the interface, which has remained undetected in static measurements. This interfacial layer likely originates from strong chemical modifications in the cobalt surface induced by chemisorbed molecules. These results underscore the crucial role of molecular chemisorption in shaping interfacial magnetic properties, offering further opportunities for tuning functionalities in molecule-based spintronic devices.