Electronic structure and magnetism of Al-doped tris(8-hydroxyquinoline)iron investigated by experiment and first-principle calculation

Abstract Room-temperature ferromagnetism was obtained in an organic, originally paramagnetic tris(8-hydroxyquinoline)iron(Feq3) molecule by doping paramagnetic aluminum atoms. The Al-doped Feq3 films were prepared on Si substrates by vacuum thermal co-evaporation. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed that all the doped Al atoms react with the O atoms of Feq3 molecule. The magnetic measurement by a physical property measurement system indicated that the Al-doped Feq3 film shows obvious ferromagnetic property even at room temperature. First-principles density functional theory (DFT) calculations were used to study the electronic structure and magnetic properties. DFT calculations results indicated that the doped Al atom tends to place at the attraction center with respect to the two O atoms of Feq3 quinoline ligands, forming –O–Al–O– complex. Compared with pure Feq3 cell, the energy differences between antiferromagnetic and ferromagnetic states became much larger after Al atoms doped into Feq3 cell. This may explain the room-temperature ferromagnetism observed in the prepared Al-doped Feq3 film.