Harvesting prominent room-temperature layered organic ferrimagnetic semiconductors: the importance of interfacial coordination

The emergence of ferromagnetism inherent to two-dimensional (2D) layered organic-inorganic semiconductors is challenging due to weak magnetic interactions at organic/inorganic interfaces. Here, layered room-temperature ferrimagnetic n-type semiconductor single crystalline nanosheets were synthesized by assembling iron vacancy doped β -Fe 3 Se 4 host layers and organic Fe(peha) (peha = pentaethylenehexamine) spacer layers. Structural optimization calculations reveal a bi-stable structure of ( β -Fe 2.75 Se 4 ) 4 [Fe(peha)], where Fe 2+ (peha) complexes can transit from coordinating with top of Fe vacancies (A-type) to apical Se atoms (B-type) of β -Fe 2.75 Se 4 host layers at higher energy levels. The as-synthetic nanosheets exhibit a magnetization under 50 kOe ( M 50 ) of 0.14 μ B /f.u. and a coercivity ( H C ) of 0.82 kOe at 300 K. Upon heating to 450 K, the structural transition from A-type to B-type coordination results in an enhanced M 50 of 0.88 μ B /f.u. while suppressing H C to 0.01 kOe, indicative of a switch from antiferromagnetic-dominated to ferromagnetic-dominated magnetic interactions at organic/inorganic interfaces. First-principles calculations confirm the interfacial coordination-dependent magnetism, where the magnetization may further increase to ∼1.1 μ B /f.u. Interfacial modification also induces obvious changes in semiconducting properties, including a maximum blue shift of 10 nm in a photoluminescence emission response at interfaces. This study offers a foundation for developing advanced organic magnetic semiconductors for room-temperature applications.