Room-Temperature Ferromagnetism in Perylene Diimide Organic Semiconductor

The development of pure organic magnets with high Curie temperatures remains a challenging task in material science. Introducing high-density free radicals to strongly interacting organic molecules may be an effective method to this end. In this study, a solvothermal approach with excess hydrazine hydrate is used to concurrently reduce and dissolve rigid-backbone perylene diimide (PDI) crystallites into the soluble dianion species with a remarkably high reduction potential. The as-prepared PDI powders comprising radical anion aggregates are fabricated by a subsequent self-assembly and spontaneous oxidation process. The results of magnetic measurements show that the PDI powders exhibit room-temperature ferromagnetism and a Curie temperature higher than 400 K, with a vast saturation magnetization that reaches ≈1.2 emu g^-1 . Elemental analysis along with the diamagnetic signal of the ablated residue are used to rule out the possibility that the magnetism is due to metal contamination. The findings suggest that the long-range ferromagnetic ordering can survive at room-temperature in organic semiconductors, and offers a new optional way to create room-temperature magnetic semiconductors.