Observation of Ferromagnetic ordering in Mn-doped tris-(8-hydroxy quinoline) aluminum

Abstract

The ferromagnetic property of Mn-doped 8-hydroxy-quinoline aluminum (Alq3), synthesized by thermal coevaporation of pure Mn metals and Alq3 powders, was investigated. The weak ferromagnetic property was observed in 5%-doped Alq3, with saturation magnetization of around 0.05μB/Mn. The doped Mn chemically interacted with O atoms, producing a new gap state at 0.34 eV above the highest occupied molecular orbital and reducing the effective electron concentration. This led to the decrease of the electron affinity and increase of the optical bandgap, resulting in the reduction of the hole-injection barrier in comparison with the electron-injection barrier to the Alq3 layer. From these, the origin of the observed ferromagnetism is suggested.