Collective Magnetism of Spin Coronoid via On-Surface Synthesis

Polyradicals obtained from open-shell coronoids hold promise for applications in spintronics and quantum technologies due to the strong interactions between spins in fully fused cyclic systems. Coronoid synthesis has long been considered difficult due to the cyclization of nanographene. It becomes an immense challenge to synthesize open-shell coronoids since radicals appear only when the macrocycle size exceeds a critical value. Here we present an open-shell coronoid with six radicals achieved through an on-surface synthesis. This spin coronoid displays a collective spin state arising from both the nearest-neighbor exchange interaction and the next-nearest-neighbor exchange interaction of six unpaired π electrons along the conjugation pathways. The characterization of the spin excitation from the ground state to the excited state was carried out by using inelastic electron tunneling spectroscopy. Additionally, we show that the spin coronoid can be utilized as a nanoscale platform to achieve short antiferromagnetic spin-1/2 Heisenberg chains through tip manipulation. Our findings present a design strategy for creating coronoids with polyradicals, which could provide inspiration for fabrication of open-shell coronoid or cyclic spintronic systems.