Magnetic properties of molecules on surfaces studied with scanning probe methods.

Magnetic molecules on surfaces provide atomically precise test beds for quantum magnetism and device concepts in spintronics and quantum information. Scanning probe techniques now resolve and control single-molecule spin states, their coupling to substrates and emergent many-body phenomena, including the Kondo effect and Yu-Shiba-Rusinov states. This review summarizes recent progress in combining molecular design, adsorption geometry and interfacial hybridization to create measurable spin anisotropy, excitations and correlations. We first recall the fundamentals of spin formation and surface-induced modifications, then survey key methodologies such as scanning tunneling microscopy, inelastic tunneling spectroscopy, pump-probe protocols, functionalized and superconducting tips, and magnetic exchange force microscopy. Case studies span single-ion magnets, metal-free Kondo-active molecules, molecular magnets on superconductors, and coupled spin architectures assembled by on-surface synthesis. Across these examples, we distill design rules for tuning exchange, anisotropy and charge transfer at the molecule-surface interface. We conclude with open challenges-reproducibility, room-temperature stability and multiscale theory-and outline opportunities in van der Waals integration, ultrafast spin dynamics and data-driven spectroscopy, charting a path from single-molecule experiments to programmable molecular spin devices.