Scanning Tunnelling Microscopy Study of Spin Interactions in Transition‐Metal Phthalocyanine Adsorbates: Mechanisms, Signatures, and Control Strategies

Spin interactions between magnetic molecules and substrates are of fundamental importance, as they offer key insights into spin-related phenomena and underpin the development of energy-efficient spintronic devices. Transition-metal phthalocyanine (TMPc) molecules serve as exemplary model systems for probing these interactions, owing to their high structural stability, tunable magnetic moments, and well-defined local environment. When adsorbed on different substrates, TMPc molecules can exhibit a rich variety of spin-related phenomena including the Kondo effect, spin excitations, and Yu-Shiba-Rusinov (YSR) states, which can be directly resolved by scanning tunnelling microscopy (STM). This review summarizes recent STM advances on the coexistence and competition of spin-related phenomena in TMPc adsorbates, emphasizing the underlying mechanisms and practical control strategies enabled by chemical design and electric- and magnetic-field stimuli, and concludes with an outlook on emerging directions for future research.