Self-assembly of 1D FeSe2 chains and Fe(dien)2 complexes for ferrimagnetic inorganic-organic hybrid cuboids

Challenges still remain in producing room-temperature ferromagnetism/ferrimagnetism in inorganic–organic hybrid compounds. Here, we report the Fe vacancy-doped inorganic–organic (Fe x Se 2 ) 2 Fe(dien) 2 (dien = diethylenetriamine, x  = 0.86) hybrid cuboids by self-assemble of finite one-dimensional (1D) FeSe 2 chains and Fe(dien) 2 complexes. A growth model is proposed by kinetically controllable syntheses of novel Fe 2x+1 Se 4 (dien) 2 hybrids. The Rietveld refinement reveals that Fe vacancies in the Fe 2.71 Se 4 (dien) 2 hybrid cuboids induce large distortions of the FeSe 2 chains and the room-temperature lattice parameters are a = 9.225(4) Å, b = 18.021(8) Å and c = 11.609(6) Å. Magnetic measurements and electron spin resonance spectra of the Fe 2.71 Se 4 (dien) 2 hybrid cuboids show the ferrimagnetism with the Curie temperature (T C ) of 600 K and the spin glass state with the freezing temperature (T f ) of 108 K. Impressive room-temperature ferrimagnetic properties of the Fe 2.71 Se 4 (dien) 2 hybrid cuboids were ascribed to the high concentration of Fe 3+ vacancies (0.29 per cell) in the hybrid cuboids, which is supported by the 57 Fe Mössbauer spectrum fitting based on the ferrimagnetic model.