Structural, electronic, and magnetic properties of tris(8-hydroxyquinoline)iron(III) molecules and its magnetic coupling with ferromagnetic surface: first-principles study

TL;DR

This study uses first-principles calculations to explore the structural, electronic, and magnetic properties of Feq3 molecules and their interaction with ferromagnetic surfaces, revealing potential for spintronic applications.

Contribution

It provides the first detailed comparison of fac- and mer-Feq3 isomers' stability, magnetic states, and their coupling with ferromagnetic surfaces using advanced DFT methods.

Findings

mer-Feq3 is more stable than fac-Feq3

High-spin state of 5 μB for both isomers with Hubbard-U

Anti-ferromagnetic coupling between Fe and Co substrate

Abstract

Using first-principles calculations, we have systematically investigated the structural, electronic, and magnetic properties of facial (fac-) and meridional (mer-) tris(8-hydroxyquinoline)iron(III) (Feq3) molecules and their interaction with ferromagnetic substrate. Our calculation results show that for the isolated Feq3, mer-Feq3 is more stable than the fac-Feq3; and both Feq3 isomers have a high spin-state of 5 {\mu}B as the ground state when an on-site Hubbard-U term is included to treat the highly localized Fe 3d electrons; while the standard DFT calculations produce a low spin-state of 1 {\mu}B. These magnetic behaviors can be understood by the octahedral ligand field splitting theory. Furthermore, we found that fac-Feq3 has a stronger bonding to the Co surface than mer-Feq3 and an anti-ferromagnetic coupling was discovered between Fe and Co substrate, originating from the superexchange coupling between Fe and Co mediated by the interface oxygen and nitrogen atoms. These findings suggest that Feq3 molecular films may serve as a promising spin-filter material in spintronic devices.